Abstract:
Disclosed is a spin valve film having a first magnetic layer, a non-magnetic layer, a second magnetic layer, and an antiferromagnetic layer as the fundamental structure for the film. In such structure of the spin valve film, a single-layered film or a multi-layered film consisting of CoZrNb, CoZrMo, FeSiAl or FeSi, or a material prepared by adding Cr, Mn, Pt, Ni, Cu, Ag, Al, Ti, Fe, Co or Zn to the above-mentioned substance is used for at least one of the first magnetic layer and second magnetic layer. According to the present invention, a thin spin valve film having a good sensitivity with respect to magnetic field and a significant magnetoresistive effect can be obtained. When using this thin film for a shield reproducing head or a yoke reproducing head, the maximum reproducing output obtainable is approximately four times that of a reproducing head which utilizes the magnetoresistive effect provided by the application of the prior art.

Description:
This is a Continuation of application Ser. No. 08/407,375 filed Mar. 20, 1995 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a magnetic head which utilizes the magnetoresistive effect. 
     2. Description of the Related Art 
     With regard to the magnetic field sensor which utilizes the variation of the magnetoresistance of a multi-layered thin film formed by laminating magnetic metal and non-magnetic conductive material, an idea is disclosed in the specification of U.S. Pat. No. 4,949,039. A spin valve film results from the development of such idea thus disclosed, and it is obtained by fixing the magnetization of a magnetic layer on one side by the provision of an antiferromagnetic layer adjacent to it. Thus, the spin valve film belongs to the subordinate conception disclosed in the U.S. Pat. No. 4,949,039. For the spin valve film, the fundamental conception is also disclosed in U.S. Pat. No. 5,206,590. In this disclosure, as materials forming each layer of the spin valve film, Co, Fe, Ni, NiFe, FeCo and NiCo are introduced as the thin film layer of the ferromagnetic elements, and Au, Ag, Cu, Pt, Pd, Cr and Ta, as the non-magnetic metallic elements, and FeMn, as the antiferromagnetic layer. 
     When NiFe is used for the spin valve film using a conventional substrate or base layer, the variation of the magnetoresistive rate for the spin valve film is made greater from 5 to 10%, but the magnetic characteristic of the NiFe varies greatly depending on crystallinity. Therefore, in order to materialize the rood sensitivity with respect to magnetic field, it is necessary to reduce the oxygen concentration in a target, and back pressure when forming a film, and to make the temperature of a substrate high and constant. Accordingly, the target purity must be enhanced, and thus, the purchase price of the target is inevitably increased. In order to reduce the back pressure at the time of film formation, a vacuum pump, a chamber and other expensive equipment are required for maintaining a high vacuum condition. Further, while a heater and other equipment are needed in the interior of the vacuum device for raising the temperature of the substrate, a heavy load is applied to the bearing and others provided for the self-revolving equipment to rotate the substrate. Such an arrangement is indispensable to obtain a thin uniform film. Also, such equipment must be operated at a high temperature, and consequently, the replacement of parts should be made more frequently, leading to an increased running cost. In addition, in order to reduce the back pressure at the time of film formation, the substrate must be left to stand for a long time after it has been set until the film formation begins, and then, the temperature of the substrate is made high in order to form the film. Therefore, after completion of the film formation, a long cooling period is needed until the spin valve film formed on the substrate can be released. To meet these requirements, it is inevitable that the frequency of film formation per unit period should be limited, thus hindering the implementation of its production on a large scale. Therefore, in order to reduce the cost of the film formation, it is necessary to obtain a magnetic material which enables the provision of good crystal more easily than NiFe or to obtain a buffer layer or a substrate on which crystal is easily grown so that NiFe can obtain a good magnetic characteristic if the NiFe should be used eventually. 
     In the prior art, Cu is used for the non-magnetic layer. In the cases where the Cu is used, it is necessary to increase the purity of the Cu target, to reduce the back pressure at the time of film formation, and to control the temperature of the substrate also at the time of film formation as in the case of the magnetic film. This arrangement inevitably leads to the increased cost of manufacturing. In order to reduce the manufacturing cost, it is required to obtain a non-magnetic material which enables the provision of a good MR characteristic more easily than the Cu. If the Cu should be used, there is a need for the arrangement of a substrate or buffer layer capable of promoting its crystal growth to obtain a good MR characteristic. 
     According to the prior art, FeMn is actually used as the antiferromagnetic material. While the FeMn and NiFe provide an exchange coupling in a good condition, there is a disadvantage that FeMn is easily subjected to oxidation. Here, in order to enhance reliability, it is necessary to obtain in place of FeMn an antiferromagnetic material which is not easily oxidized in the air and the characteristics of which are not easily deteriorated, or if the FeMn should be used, it is required to provide a protective film to prevent the FeMn layer from being in contact with the air so that it may be oxidized with difficulty. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a spin valve film which is superior to the conventional one in terms of the reliability and the manufacturing cost, and also, is capable of presenting a higher MR ratio and a better characteristics of the head output than those of the conventional spin valve film. 
     In a spin valve film having a first magnetic layer/a non-magnetic layer/a second magnetic layer/an antiferromagnetic layer as its fundamental structure of the film, a single-layered film or a multi-layered film formed of CoZrNb, CoZrMo, FeSiAl or FeSi is used for at least one of the first magnetic layer and the second magnetic layer. It may be possible to use for the non-magnetic layer a single-layered film or a multi-layered film formed of a single substance selected from Al, Si, Ti, Ir, V, Cu, Zn, Zr, Nb, Mo, Pd, Ag, Sn, Hf, Ta, W, Pt, Au, Pb, Bi, C and silicon carbide or a mixture thereof. As the antiferromagnetic layer, a single-layered film or a multi-layered film formed of a single substance selected from FeMn, NiO, CoO, FeO, Fe 2  O 3 , MnO, CrO, Cr and Mn, a mixture thereof, or a material prepared by adding to the substance or mixture Mo, W, V, Ir, Nb, Ta, Mn, Tc, Re, Ru, Rh, Fe, Co, Ni, Pt, Pd, Au, Ag or Cu may be used. For the first or second magnetic layer, a single-layered film or a multi-layered film formed of a material to which Cr, Mn, Pt, Ni, Ir, Cu, Ag, Al, Ti, Fe, Co or Zn is added may be used. 
     Or, in a spin valve film having a first magnetic layer/a non-magnetic layer/a second magnetic layer/an antiferromagnetic layer as its fundamental structure of the film, at least one of the first magnetic layer and the second magnetic layer is formed of either NiFe or NiFeCo, and for the non-magnetic layer, a single-layered film or a multi-layered film formed of a single substance selected from Al, Si, Ti, Ir, V, Zn, Zr, Nb, Mo, Pd, Ag, Sn, Hf, Ta, W, Pt, Au, Pb, Bi, C or silicon carbide or a mixture thereof is used. In this case, as the antiferromagnetic layer, a single-layered film or a multi-layered film formed of a single substance selected from CoO, FeO, Fe 2  O 3 , MnO, CrO, Cr and Mn, a mixture thereof, or a material prepared by adding Mo, W, V, Ir, Nb, Ta, Mn, Tc, Re, Ru, Rh, Fe, Co, Ni, Pt, Pd, Au, Ag or Cu to the substance or the mixture may be used. It may be possible to provide a constitution in which the first magnetic layer or the antiferromagnetic layer is in contact with the substrate or the buffer layer formed on the substrate. It may also be possible to arrange a constitution in which a protective layer is provided on the outermost layer. 
     In addition, at least one of the first magnetic layer and the second magnetic layer may be formed of CoZrNb, CoZrMo, FeSiAl or FeSi, and for the substrate, a single-layered film or a multi-layered film may be formed of glass, ceramic, metal, metallic compound or plastic, or a mixture of these materials. A single-layered film or a multi-layered film formed of a single substance selected from Ta, Hf, Si, Au, Pt, Ag, Cu, Ti, Mn, Cr, Al, Si nitride, Si oxides, Al oxide, AlN, Al nitride, SiC and C or a mixture thereof may be used for the buffer layer. For the protective layer, a single-layered film or a multi-layered film formed of Ta, Hf, Si, Au, Pt, Ag, Cu, Mn, Ti, Cr, Al, Si nitride, Si oxides, Al oxide, Al nitride, SiC, C or diamond-like carbon, or a mixture or alloy of these substances may be used. At least one of the first magnetic layer and the second magnetic layer is formed of NiFe or NiFeCo, and fundamentally, it may be possible to use a single-layered film or a multi-layered film formed of ceramic, metal, metallic compound or plastic or a mixture of these materials. For the buffer layer, a single-layered film or a multi-layered film formed of a single substance selected from Si, Au, Pt, Ag, Cu, Ti, Mn, Cr, Al, Si 3  N 4 , Si nitride, SiO 2 , Si nitride, Al 2  O 3 , Al oxide, AlN, Al nitride, SiC, C and diamond-like carbon or a mixture thereof may be used. For the protective layer, a single-layered film or a multi-layered film formed of Ta, Hf, Si, Au, Pt, Ag, Ti, Cr, Al, Si nitride, Si oxides, Al oxide, Al nitride, SiC, C or diamond-like carbon, or a mixture or alloy thereof. The film thickness of at least one of the first magnetic layer and the second magnetic layer may be 5 to 30 nm. The film thickness of the non-magnetic layer may be 2 to 5 nm. The film thickness of the antiferromagnetic layer may be 10 to 100 nm. The film thickness of the metallic protective layer may be 3 nm or less. The film thickness of the non-metallic protective layer may be 2 nm or more. The film thickness of the metallic buffer layer may be 15 nm or less. The film thickness of the non-metallic buffer layer may be 5 nm or more. 
     CoZrNb and CoZrMo, and a material obtained by adding Cr, Mn, Pt, Ni, Cu, Ag, Ir, Al, Ti, Fe, Co or Zn to CoZrNb or CoZrMo become amorphous when film formation is performed using usual sputtering. Therefore, if any of the above-mentioned material is used for a substrate or a buffer layer, good magnetic characteristics can be obtained even in the case where special attention is not paid to the back pressure during the film formation and target purity as compared to the case where NiFe and others are used. Also, since FeSiAl and FeSi are materials having body-centered cubic structure, and good crystallinity, it is easier to form a film having a good crystal, and obtain a good magnetic characteristic if such materials are used. 
     Also, when Ag, Au, an alloy of Ag and Au or a material prepared by adding to Ag or Au a single substance selected from Al, Si, Ti, Ir, V, Cu, Zn, Zr, Nb, Mo, Pd, Sn, Hf, Ta, W, Pt, Pb, Bi and C or some of the substances in combination is used for the non-magnetic layer, the current characteristic of the film hardly changes with time because the Ag or Au is a material which is hardly oxidized, and presents a nature which does not allow the interfacial diffusion to occur easily between the magnetic layer and the non-magnetic layer due to its wettability. Also, when a material prepared by adding to Cu a single substance selected from Al, Si, Ti, Ir, V, Zr, Nb, Mo, Pd, Sn, Hf, Ta, W and Bi or a plurality of the substances is used for the non-magnetic layer, the reliability is enhanced because the element thus added can adsorb the element such as oxygen that may promote the change of the current characteristic with passage of time. Also, when Ti, Ir, V, Zn, Pd, Sn, Hf, Ta, W, Pt, Pb, Bi or C is added to Cu, it is anticipated that these elements function to moderate the interfacial diffusion of the Cu to the magnetic layer. 
     In addition, among the antiferromagnetic materials, a single substance selected from NiO, CoO, FeO, Fe 2  O 3 , MnO and CrO, a mixture thereof, or a material prepared by adding to the substance or mixture Mo, W, V, Ir, Nb, Ta, Mn, Tc, Re, Ru, Rh, Fe, Co, Ni, Pt, Pd, Au, Ag or Cu is stable in the air because the main component thereof is an oxide. The single substance of Cr and Mn, a mixture thereof or a material prepared by adding to the substance or mixture Mo, W, V, Ir, Nb, Ta, Mn, Tc, Re, Ru, Rh, Fe, Co, Ni, Pt, Pd, Au, Ag or Cu is stable in the air because both Mn and Cr are materials which are comparatively hardly oxidized although the main component is metal. 
     When a single-layered film or a multi-layered film formed of Ta, Hf, Si, Au, Pt, Ag, Cu, Mn, Ti, Cr, Al, Si nitride, Si oxides, Al oxide, Al nitride, SiC, C or diamond-like carbon, or a mixture or alloy of these substances is used as a protective layer on the outermost layer, the protective layer functions to prevent the magnetic layer, non-magnetic layer, and antiferromagnetic layer from being in contact with the air. Therefore, the reliability of the spin valve film can be securely obtained even when a material that may comparatively be oxidized easily is used for the magnetic layer, non-magnetic layer, and antiferromagnetic layer. 
     When a crystalline material is used for the magnetic layer and non-magnetic layer, the combination of substrate and buffer layer affects the crystallinity of the material although its degree depends on the material to be used. If the single substance of Si 3  N 4 , SiO 2 , AlN and Al 2  O 3 , a mixture thereof, a laminated film or glass is used for the substrate, it is effective to use a single-layered film or a multi-layered film formed of the single substance of Au, Pt, Ag, Cu, Ti, Mn, Cr and Al or a mixture thereof for the buffer layer. When a plastic such as polycarbonate, vinyl chloride, polyimide, polyolefin, and a mixture or laminated film of these materials is used for the substrate, it is possible to obtain the similar effect as in the case where the single substance of Si 3  N 4 , SiO 2 , AlN, Al 2  O 3  and glass or a mixture thereof and a laminated film is used for a substrate if a single substance of silicon oxides, silicon nitride, aluminum oxide, aluminum nitride, other ceramics, glass, a mixture thereof, or a laminated film is formed on the substrate as a first buffer layer, and further thereon, a single-layered film or a multi-layered film formed of a single substance of Au, Pt, Ag, Cu, Ti, Mn, Cr and Al or a mixture thereof is provided as a second buffer layer. On the other hand, when an amorphous material such as CoZrNb and CoZrMo is used for the magnetic layer, it is possible to use for the buffer layer the single substance of Au, Pt, Ag, Cu, Ti, Mn, Cr, Al, silicon oxides, silicon nitride, aluminum oxide, aluminum nitride, other ceramics, glass, SiC, C, diamond-like carbon and the like, a mixture, or laminated film thereof because the buffer layer is not required to provide properties that may promote the crystallinity of the film. 
     If the film thickness of the magnetic layer is too small, it becomes difficult to allow a good inversion of spin to take place following the impression of the magnetic field. On the other hand, if it is too large, the magnitude of the coupled magnetic field becomes too small because the magnitude of the coupled magnetic field of the exchange coupling film is proportional to the film thickness. As a result, there is an appropriate range for setting a film thickness. 
     If the film thickness of the non-magnetic layer is too small, the exchange coupling between the first magnetic layer and the second magnetic layer becomes too strong. Therefore, it becomes difficult for the second magnetic layer to generate its inversion. On the other hand, if it is too large, the MR ratio of the spin valve film is lowered because the rate of dependency of the diffusion of electron in the direction of magnetization becomes small on the interface between the magnetic layer and non-magnetic layer. As a result, there is an appropriate range for setting a film thickness. 
     When a conductive protective layer and a conductive buffer layer are used, the electric resistance of the spin valve film is lowered as a whole, thus lowering the amount of change in the magnetoresistance if the film thickness is too large. The film thickness of the conductive protective layer and the buffer layer should not be too large. 
     If the non-conductive protective layer and buffer layer are used, it may be possible to make the film thickness larger to a certain extent because the amount of change in the magnetoresistance is not affected even when the film thickness is large. There are better cases where the film thickness is made larger to a certain extent taking the reliability and the crystal growth into consideration. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings, in which: 
     FIG. 1 is a conceptional view showing a spin valve film according to the present invention; 
     FIG. 2 is a conceptional view showing a spin valve film according to the present invention; 
     FIG. 3 is a conceptional view showing a spin valve film according to the present invention; 
     FIG. 4 is a conceptional view showing a spin valve film according to the present invention; 
     FIG. 5 is a conceptional view showing a spin valve film according to the present invention; 
     FIG. 6 is a conceptional view showing a spin valve film according to the present invention; 
     FIG. 7 is a conceptional view showing a spin valve film according to the present invention; and 
     FIG. 8 is a conceptional view showing a spin valve film according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described below in detail by way of Examples. 
     EXAMPLE 1 
     In a structure shown in FIG. 1, a spin valve film was produced by changing the composition of the first magnetic layer and second magnetic layer as shown in Table 1, and using the antiferromagnetic layer of (1), (2) or (3) given below. Then, the inverted magnetic field and the rate of change of the magnetoresistance of the second magnetic layer were measured. 
     Next, using this spin valve film, a shield reproducing head and a yoke reproducing head were produced to conduct reading tests on a magnetic domain having a width of 0.3 μm recorded on a commercially available hard disk by use of an inductive head. The inverted magnetic field, the rate of change of the magnetoresistance, and the value of reproducing output of the second magnetic layer in this case are shown in each table. The same magnetic domain was reproduced by use of the conventional MR head to give the reproducing signal of 260 μV. Thus, the reproducing signal presented an improvement of two to four times. 
     (1) In the case where NiO is used for the antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, silicon nitride as the buffer layer (10 nm), Cu as the non-magnetic layer (3 nm), NiO as the antiferromagnetic layer (30 nm) and copper as the protective layer (2 nm) and by changing the composition of the first and second magnetic layers as shown in Table 1 while their film thickness being made 15 nm in these cases. The result of measurement is also shown in Table 1. 
     Table 1 
     (2) In the case where FeMn is used for the antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, silicon nitride as the buffer layer (10 nm), Cu as the non-magnetic layer (3 nm), FeMn as the antiferromagnetic layer (10 nm) and copper as the protective layer (2 nm) and by changing the composition of the first and second magnetic layers as shown in Table 2 while their film thickness being made 15 nm in these cases. The result of measurement is also shown in Table 2. 
     Table 2 
     (3) In the case where a mixture of CoO and Nio is used for the antiferromagnetic layer: 
     a spin valve film was produced using Al 2  O 3  glass as the substrate, TA as the buffer layer (15 nm), Ag as the non-magnetic layer (3 nm), a mixture of CoO and NiO as the antiferromagnetic layer (40 nm) and copper as the protective layer (2 nm) and by changing the composition of the first and second magnetic layers as shown in Table 3 while their film thickness being made 12 nm and 16 nm, respectively. The result of measurement is also shown in Table 3. 
     Table 3 
     EXAMPLE 2 
     In the structure shown in FIG. 1, a spin valve film was produced by changing the composition of the non-magnetic layer and using the first and second magnetic layers of (1) and (2) given below. Then, the inverted magnetic field and the rate of change of magnetoresistance of the second magnetic layer were measured. Also, in the same manner as in Example 1, the inverted magnetic field, the rate of change of magnetoresistance, and the value of reproducing output of the second magnetic layer of shield and yoke reproducing heads were measured. 
     (1) In the case where FeSiAl is used for both the first and second magnetic layers: 
     a spin valve film was produced using SiO 2  as the substrate, Hf nitride as the buffer layer (10 nm), FeSiAl as the first magnetic layer (15 nm), FeSiAl as the second magnetic layer (20 nm) and a mixture of FeO, NiO and CoO as the antiferromagnetic layer (35 nm), and copper as the protective layer (2 nm) and by changing the composition of the non-magnetic layer as shown in Table 4 while its film thickness being made 3 nm in these cases. The result of measurement is also shown in Table 4. 
     Table 4 
     (2) In the case where FeSiAl is used for the first magnetic layer and NiFe for the second magnetic layer: 
     a spin valve film was produced using SiO 2  as the substrate, Al nitride as the buffer layer (10 nm), FeSiAl as the first magnetic layer (15 nm), NiFe as the second magnetic layer (13 nm), FeMn as the antiferromagnetic layer (8 nm) and copper as the protective layer (3 nm) and by changing the composition of the non-magnetic layer as shown in Table 5 while its film thickness being made 3 nm in these cases. The result of measurement is also shown in Table 5. 
     Table 5 
     EXAMPLE 3 
     In the structure shown in FIG. 1, a spin valve film was produced by changing the composition of the antiferromagnetic layer and using the first and second magnetic layers of (1) and (2) given below. Then, the inverted magnetic field and the rate of change of magnetoresistance of the second magnetic layer were measured. Also, in the same manner as in Example 1, the inverted magnetic field, the rate of change of magnetoresistance, and the value of reproducing output of the second magnetic layer of shield and yoke reproducing heads were measured. 
     (1) In the case where FeSiAl is used for the first magnetic layer and CoZrNb for the second magnetic layer: 
     a spin valve film was produced using glass as the substrate, Au as the buffer layer (8 nm), FeSiAl as the first magnetic layer (10 nm), Al as the non-magnetic layer (2.5 nm), CoZrNb as the second magnetic layer (16 nm) and copper as the protective layer (2 nm) and by changing the composition of the antiferromagnetic layer as shown in Table 6 while its film thickness being made 12 nm in these cases. The result of measurement is also shown in Table 6. 
     Table 6 
     (2) In the case where FeSiAl is used for the first magnetic layer and NiFeCo for the second magnetic layer: 
     a spin valve film was produced using glass as the substrate, Si 2  O 3  as the buffer layer (11 nm), FeSiAl as the first magnetic layer (16 nm), Ag as the non-magnetic layer (3.5 nm), NiFe as the second magnetic layer (14 nm) and Ag as the protective layer (2 nm) and by changing the composition of the antiferromagnetic layer as shown in Table 7 while its film thickness being made 18 nm in these cases. The result of measurement is also shown in Table 7. 
     Table 7 
     EXAMPLE 4 
     In the structure shown in FIG. 1, a spin valve film was produced by using the antiferromagnetic layer of (1) or (2) given below and changing the elements to be added thereto. Then, the inverted magnetic field and the rate of change of magnetoresistance of the second magnetic layer were measured. Also, in the same manner as in Example 1, the inverted magnetic field, the rate of change of magnetoresistance, and the value of reproducing output of the second magnetic layer of shield and yoke reproducing heads were measured. 
     (1) In the case where elements are added to the FeMn antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, Pt as the buffer layer (15 nm), FeSiAl as the first magnetic layer (15 nm), Cu as the non-magnetic layer (2.5 nm), NiFe as the second magnetic layer (16 nm) and Ag as the protective layer (2 nm) and by adding various elements to the FeMn antiferromagnetic layer (12 nm) as shown in Table 8. The result of measurement is also shown in Table 8. 
     Table 8 
     (2) In the case where elements are added to the NiO antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, a glass-sputtered film as the buffer layer (20 nm), NiFe as the first magnetic layer (20 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (20 nm) and Cu as the protective layer (2 nm) and by adding various elements to the NiO antiferromagnetic layer (17 nm) as shown in Table 9. The result of measurement is also shown in Table 9. 
     Table 9 
     EXAMPLE 5 
     In the structure shown in FIG. 1, a spin valve film was produced by changing the composition of the buffer layer and using the first and second magnetic layers of (1) and (2) given below. Then, the inverted magnetic field and the rate of change of magnetoresistance of the second magnetic layer were measured. Also, in the same manner as in Example 1, the inverted magnetic field, the rate of change of magnetoresistance, and the value of reproducing output of the second magnetic layer of shield and yoke reproducing heads were measured. 
     (1) In the case where the first magnetic layer is NiFe, and the second magnetic layer is FeSiAl: 
     a spin valve film was produced using glass as the substrate, NiFe as the first magnetic layer (15 nm), Al as the non-magnetic layer (3 nm), FeSiAl as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and copper as the protective layer (2 nm) and by changing the composition of the buffer layer as shown in Table 10 while its film thickness being made 15 nm in these cases. The result of measurement is also shown in Table 10. 
     Table 10 
     (2) In the case where the first magnetic layer is NiFe and the second magnetic layer is CoZrNb: 
     a spin valve film was produced using glass as the substrate, NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), CoZrNb as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and copper as the protective layer (2 nm) and by changing the composition of the buffer layer as shown in Table 11 while its film thickness being made 15 nm in these cases. The result of measurement is also shown in Table 11. 
     Table 11 
     EXAMPLE 6 
     In the structure shown in FIG. 1, a spin valve film was produced by changing the composition of the protective layer and using the antiferromagnetic layer of (1) and (2) given below. Then, the inverted magnetic field, and the rate of change of magnetoresistance of the second magnetic layer were measured. Also, in the same manner as in Example 1, the inverted magnetic field, the rate of change of magnetoresistance, and the value of reproducing output of the second magnetic layer of shield and yoke reproducing heads were measured. 
     (1) In the case where NiO is used for the antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, Hf as the buffer layer (10 nm), FeSiAl as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), FeSiAl as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (15 nm) and by changing the composition and thickness of the protective layer as shown in Table 12. The result of measurement is also shown in Table 12. 
     Table 12 
     (2) In the case where FeMn is used for the antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, SiO 2  as the buffer layer (10 nm), NiFe as the first magnetic layer (12 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (16 nm) and FeMn as the antiferromagnetic layer (15 nm) and by changing the composition and thickness of the protective layer as shown in Table 13. The result of measurement is also shown in Table 13. 
     Table 13 
     EXAMPLE 7 
     In the structure shown in FIG. 1, a spin valve film was produced by changing the material of the substrate and using the buffer layer of (1) and (2) given below. Then, the inverted magnetic field and the rate of change of magnetoresistance of the se cond magnetic layer were measured. Also, in the same manner as Example 1, the inverted magnetic field, the rate of change of magnetoresistance, and the value of reproducing output of the second magnetic layer of shield and yoke reproducing heads were measured. 
     (1) I n the case where Hf is used for t he buffer layer: 
     a spin valve film was produced using Hf as the buffer layer (10 nm), FeSiAl as the first magnetic layer (17 nm), Cu as the non-magnetic layer (3 nm), FeSiAl as the second magnetic layer (17 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm) and by changing the composition of the substrate as shown in Table 14. The result of measurement is also shown in Table 14. 
     Table 14 
     (2) In the case where Si 3  N 4  is used for the buffer layer: 
     a spin valve film was produced using Si 3  N 4  as the buffer layer (80 nm), NiFe as the first magnetic layer (14 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (14 nm), FeMn as the antiferromagnetic layer (15 nm) and Si 3  N 4  as the protective layer (80 nm) and by changing the composition of the substrate as shown in Table 15. The result of measurement is also shown in Table 15. 
     Table 15 
     EXAMPLE 8 
     In each of the elemental structures of the spin valve film shown in FIG. 1 to FIG. 8, the inverted magnetic field and the rate of change of magnetoresistance of 5.5% were measured for the second magnetic layer by use of the first and second magnetic layers of (1) and (2) given below. 
     Then, a shield reproducing head and a yoke reproducing head were produced using the respective spin valve films, and the reading tests were performed on the magnetic domain having a width of 0.3 μm recorded on a commercially available hard disk by use of an inductive head. 
     (1) In the case where the first magnetic layer is CoZrMo and the second magnetic layer is CoZrNb: 
     (a) When a spin valve film was produced in the structure as shown in FIG. 1 using Al 2  O 3  as the substrate, Ta as the buffer layer (10 nm), CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (50 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 30e and the rate of change of magnetoresistance of 5.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 890 μV and 960 μV, respectively. 
     (b) When a spin valve film was produced in the structure as shown in FIG. 2 using Al 2  O 3  as the substrate, CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (50 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 870 μV and 920 μV, respectively. 
     (c) When a spin valve film was produced in the structure as shown in FIG. 3 using Al 2  O 3  as the substrate, CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (50 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 6% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 910 μV and 940 μV, respectively. 
     (d) When a spin valve film was produced in the structure as shown in FIG. 4 using Al 2  O 3  as the substrate, Ta as the buffer layer (10 nm), CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (50 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 6% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 920 μV and 960 μV, respectively. 
     (e) When a spin valve film was produced in the structure as shown in FIG. 5 using Al 2  O 3  as the substrate, CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm) and NiO as the antiferromagnetic layer (50 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 830 μV and 880 μV, respectively. 
     (f) When a spin valve film was produced in the structure as shown in FIG. 6 using Al 2  O 3  as the substrate, Ta as the buffer layer (10 nm), CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (50 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 5.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 870 μV and 860 μV, respectively. 
     (g) When a spin valve film was produced in the structure as shown in FIG. 7 using Al 2  O 3  as the substrate, CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (50 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 5.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 870 μV and 860 μV, respectively. 
     (h) When a spin valve film was produced in the structure as shown in FIG. 8 using Al 2  O 3  as the substrate, Ta as the buffer layer (10 nm), CoZrMo as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (50 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 30e and the rate of change of magnetoresistance of 6% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 890 μV and 940 μV, respectively. 
     (2) In the case where both of the first and second magnetic layers are NiFe: 
     (a) When a spin valve film was produced in the structure as shown in FIG. 1 using glass as the substrate, Hf as the buffer layer (10 nm), NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm) Nio as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 6.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 830 μV and 870 μV, respectively. 
     (b) When a spin valve film was produced in the structure as shown in FIG. 2 using glass as the substrate, NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (15 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 5.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 770 μV and 840 μV, respectively. 
     (c) When a spin valve film was produced in the structure as shown in FIG. 3 using glass as the substrate, NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 40e and the rate of change of magnetoresistance of 6% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 690 μV and 750 μV, respectively. 
     (d) When a spin valve film was produced in the structure as shown in FIG. 4 using glass as the substrate, Hf as the buffer layer (10 nm), NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (15 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 5.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 800 μV and 810 μV, respectively. 
     (e) When a spin valve film was produced in the structure as shown in FIG. 5 using glass as the substrate, NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (15 nm), there were obtained the inverted magnetic field of 50e and the rate of change of magnetoresistance of 5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 680 μV and 740 μV, respectively. 
     (f) When a spin valve film was produced in the structure as shown in FIG. 6 using glass as the substrate, Hf as the buffer layer (10 nm), NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm) and NiO as the antiferromagnetic layer (15 nm), there were obtained the inverted magnetic field of 60e and the rate of change of magnetoresistance of 5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 720 μV and 750 μV, respectively. 
     (g) When a spin valve film was produced in the structure as shown in FIG. 7 using glass as the substrate, NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 70e and the rate of change of magnetoresistance of 5.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 810 μV and 830 μV, respectively. 
     (h) When a spin valve film was produced in the structure as shown in FIG. 8 using glass as the substrate, Hf as the buffer layer (10 nm), NiFe as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 40e and the rate of change of magnetoresistance of 5.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 760 μV and 840 μV, respectively. 
     EXAMPLE 9 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the first magnetic layer of (1) or (2) given below and changing its film thickness. A shield reproducing head and a yoke reproducing head were manufactured by use of this spin valve film. Then, reading tests were performed on the magnetic domain having a width of 0.3 gm recorded on a commercially available hard disk by use of an inductive head. 
     (1) In the case where FeSiAl is used for the first magnetic layer: 
     a spin valve film was produced using glass as the substrate, Hf as the buffer layer (10 nm), Cu as the non-magnetic layer (3 nm), FeSiAl as the second magnetic layer (17 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm) and by changing the film thickness of the FeSiAl first magnetic layer as shown in Table 16. The values of the reproducing output are also shown in Table 16. 
     Table 16 
     (2) In the case where NiFe is used for the first magnetic layer: 
     a spin valve film was produced using glass as the substrate, SiO 2  as the buffer layer (80 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and SiO 2  as the protective layer (80 nm) and by changing the film thickness of the NiFe first magnetic layer as shown in Table 17. The values of the reproducing output are also shown in Table 17. 
     Table 17 
     EXAMPLE 10 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the second magnetic layer of (1) or (2) given below and changing its film thickness. The values of reproducing outputs of a shield reproducing head and a yoke reproducing head were measured in the same manner as in Example 9. 
     (1) In the case where CoZrNb is used for the second magnetic layer: 
     a spin valve film was produced using glass as the substrate, Ta as the buffer layer (10 nm), Cu as the non-magnetic layer (3 nm), CoZrMo as the first magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm) and by changing the film thickness of the CoZrMb second magnetic layer as shown in Table 18. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 18, respectively. 
     Table 18 
     (2) In the case where NiFe is used for the second magnetic layer: 
     a spin valve film was produced using glass as the substrate, Al 2  O 3  as the buffer layer (30 nm), Cu as the non-magnetic layer (3 nm), NiFe as the first magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and Al 2  O 3  as the protective layer (50 nm) and by changing the film thickness of the NiFe second magnetic layer as shown in Table 19. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 19, respectively. 
     Table 19 
     EXAMPLE 11 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the non-magnetic layer of (1) or (2) given below and changing its film thickness. The values of reproducing outputs of a shield reproducing head and a yoke reproducing head were measured in the same manner as in Example 9. 
     (1) In the case where Cu is used for the non-magnetic layer: 
     a spin valve film was produced using glass as the substrate, Cr as the buffer layer (10 nm), NiFe as the first magnetic layer (17 nm), FeSiAl as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm) and by changing the film thickness of the Cu non-magnetic layer as shown in Table 20. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 20, respectively. 
     Table 20 
     (2) In the case where Al is used for the non-magnetic layer: 
     a spin valve film was produced using glass as the substrate, AlN as the buffer layer (30 nm), CoZrMo as the first magnetic layer (17 nm), FeSiAl as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and SiO 2  as the protective layer (30 nm) and by changing the film thickness of the Al non-magnetic layer as shown in Table 21. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 21, respectively. 
     Table 21 
     EXAMPLE 12 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the antiferromagnetic layer of (1) or (2) given below and changing its film thickness. The values of reproducing outputs of a shield reproducing head and a yoke reproducing head were measured in the same manner as in Example 9. 
     (1) In the case where FeMn is used for the antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, Ta as the buffer layer (10 nm), NiFe as the first magnetic layer (18 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (14 nm) and Cu as the protective layer (2 nm) and by changing the film thickness of the FeMn ferromagnetic layer as shown in Table 22. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 22, respectively. 
     Table 22 
     (2) In the case where a mixture of NiO, CoO, and FeO is used for the antiferromagnetic layer: 
     a spin valve film was produced using glass as the substrate, Pt as the buffer layer (10 nm), FeSiAl as the first magnetic layer (16 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (18 nm) and Pt as the protective layer (2 nm) and by changing the film thickness of the ferromagnetic layer formed of NiO, CoO and FeO as shown in Table 23. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 23, respectively. 
     Table 23 
     EXAMPLE 13 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the metallic protective layer of (1) or (2) given below and changing its film thickness. The values of reproducing outputs of a shield reproducing head and a yoke reproducing head were measured in the same manner as in Example 9. 
     (1) In the case where Cu is used for the metallic protective layer: 
     a spin valve film was produced using glass as the substrate, Mo as the buffer layer (10 nm), NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and Cu as the protective layer and by changing the film thickness of the Cu protective layer as shown in Table 24. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 24, respectively. 
     Table 24 
     (2) In the case where an AgTi alloy is used for the metallic protective layer: 
     a spin valve film was produced using glass as the substrate, Si 3  N 4  as the buffer layer (50 nm), SiAlTi as the first magnetic layer (13 nm), Au as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and AgTi alloy as the protective layer and by changing the film thickness of the AgTi alloy protective layer as shown in Table 25. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 25, respectively. 
     Table 25 
     EXAMPLE 14 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the non-metallic protective layer of (1) or (2) given below and changing its film thickness. The values of reproducing outputs of a shield reproducing head and a yoke reproducing head were measured in the same manner as in Example 9. 
     (1) In the case where Si 3  N 4  is used for the non-metallic protective layer: 
     a spin valve film was produced in the structure shown in FIG. 1 using glass as the substrate, Si 3  N 4  as the buffer layer (80 nm), NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and Si 3  N 4  as the protective layer and by changing the film thickness of the Si 3  N 4  protective layer as shown in Table 26. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 26, respectively. 
     Even when the film thickness of the protective layer is varied as described above, there are almost no changes in the head reproducing outputs. However, if the film thickness is made less than 2 nm, the FeMn antiferromagnetic layer is conspicuously oxidized, thus causing a problem with respect to reliability. 
     Table 26 
     (2) In the case where an Al 2  O 3  alloy is used for the non-metallic protective layer: 
     a spin valve film was produced using glass as the substrate, Al 2  O 3  as the buffer layer (80 nm), FeSiAl as the first magnetic layer (14 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (16 nm), FeMn as the antiferromagnetic layer (15 nm) and Al 2  O 3  as the protective layer and by changing the film thickness of the Al 2  O 3  protective layer as shown in Table 27. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 27, respectively. 
     Even when the film thickness of the protective layer is varied as described above, almost no changes are found in the head reproducing outputs. However, if the film thickness is made less than 2 nm, there is a tendency that the FeMn antiferromagnetic layer is conspicuously oxidized. 
     Table 27 
     EXAMPLE 15 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the metallic buffer layer of (1) or (2) given below and changing its film thickness. The values of reproducing outputs of a shield reproducing head and a yoke reproducing head were measured in the same manner as in Example 9. 
     (1) In the case where a CuPtAuAg alloy is used for the metallic buffer layer: 
     a spin valve film was produced using glass as the substrate, CuPtAuAg alloy as the buffer layer, NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and Si 3  N 4  as the protective layer (50 nm) and by changing the film thickness of the CuPtAuAg alloy buffer layer as shown in Table 28. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 28, respectively. 
     Table 28 
     (2) In the case where Ta is used for the metallic buffer layer: 
     a spin valve film was produced using glass as the substrate, Ta as the buffer layer, CoZrMo as the first magnetic layer (15 nm), Ag as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and Si 3  N 4  as the protective layer (50 nm) and by changing the film thickness of the buffer layer as shown in Table 29. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 29, respectively. 
     Table 29 
     EXAMPLE 16 
     In the structure as shown in FIG. 1, a spin valve film was produced by using the non-metallic buffer layer of (1) or (2) given below and changing its film thickness. The values of reproducing outputs of a shield reproducing head and a yoke reproducing head were measured in the same manner as in Example 9. 
     (1) In the case where Si 3  N 4  is used for the metallic buffer layer: 
     a spin valve film was produced using SiO 2  as the substrate, Si 3  N 4  as the buffer layer, NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and Si 3  N 4  as the protective layer (50 nm) and by changing the film thickness of the buffer layer as shown in Table 30. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 30, respectively. 
     Table 30 
     (2) In the case where a mixture of SiO 2 , Si 3  N 4 , AlN, and Al 2  O 3  is used for the non-metallic buffer layer: 
     a spin valve film was produced using garnet as the substrate, a mixture of SiO 2 , Si 3  N 4 , AlN and Al 2  O 3  as the buffer layer, FeSi as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), NiFe as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and AlN as the protective layer (60 nm) and by changing the film thickness of the buffer layer as shown in Table 31. The values of the reproducing outputs of the shield and yoke reproducing heads are also shown in Table 31, respectively. 
     Table 31 
     EXAMPLE 17 
     In the structure as shown in FIG. 1, the magnetic layers were formed under the conditions of (1) to (5) given below. The inverted magnetic field and the rate of change of the magnetoresistance of the second magnetic layer were measured. 
     Then, a shield reproducing head and a yoke reproducing head were manufactured by use of a spin valve film thus produced. Reading tests were performed on the magnetic domain having a width of 0.3 μm recorded on a commercially available hard disk by use of an inductive head. Then, the values of reproducing output were obtained. 
     (1) In the case where a double-layered film is used for the first magnetic layer: 
     When a spin valve film was produced using Al 2  O 3  as the substrate, Ti as the buffer layer (10 nm), a double-layered film of CoZrMo (5 nm)/CoZrNb (10 nm) as the first magnetic layer, Cu as the non-magnetic layer (3.5 nm), CoZrNb as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 7% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 930 μV and 970 μV, respectively. 
     (2) In the case where an eight-layered film is used for the first magnetic layer: 
     When a spin valve film was produced using Al 2  O 3  as the substrate, Ti as the buffer layer (10 nm), an eight-layered film of (CoZrMo (2 nm)/CoZrNb (2 nm))×4 as the first magnetic layer, Cu as the non-magnetic layer (3 nm), CoZrNb as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 8% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 1070 μV and 1130 μV, respectively. 
     (3) In the case where a three-layered film is used for the second magnetic layer: 
     When a spin valve film was produced using glass as the substrate, W as the buffer layer (10 nm), FeSiAl as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), a three-layered film of FeNi (5 nm)/FeSiAl (5 nm)/FeSi (5 nm) as the second magnetic layer, FeMn as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 6.5% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 910 μV and 940 μV, respectively. 
     (4) In the case where a 16-layered film is used for the second magnetic layer: 
     When a spin valve film was produced using glass as the substrate, W as the buffer layer (10 nm), FeSiAl as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), a 16-layered film of (FeNi (1 nm)/FeSiAl (1 nm))×8 as the second magnetic layer, FeMn as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 7% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 950 μV and 930 μV, respectively. 
     (5) In the case where a 16-layered film is used for the first magnetic layer and another 16-layered film is used for the second magnetic layer: 
     When a spin valve film was produced using glass as the substrate, Si 3  N 4  as the buffer layer (80 nm), a 16-layered film of (NiFe (1 nm)/FeSiAl (1 nm))×8 as the first magnetic layer, Cu as the non-magnetic layer (3 nm), a 16-layered film of (FeNi (1 nm)/FeSiAl (1 nm))×8 for the second magnetic layer, FeMn as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 9% for the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 1270 μV and 1300 μV, respectively. 
     EXAMPLE 18 
     In the structure shown in FIG. 1, the non-magnetic layers were formed under the conditions of (1) and (2) given below. The inverted magnetic field and the rate of change of the magnetoresistance of the second magnetic layer were measured. Also, the reproducing output value of the shield reproducing head and that of the yoke reproducing head were measured in the same manner as in Example 17. 
     (1) In the case where a double-layered film is used for the non-magnetic layer: 
     When a spin valve film was produced using glass as the substrate, Si 3  N 4  as the buffer layer (80 nm), a 16-layered film of (NiFe (1 nm)/FeSiAl (1 nm))×8 as the first magnetic layer, a double-layered film of Au (1.5 nm)/Ag (1.5 nm) as the non-magnetic layer, a 16-layered film of (FeNi (1 nm)/FeSiAl (1 nm))×8 as the second magnetic layer, FeMn as the antiferromagnetic layer (15 nm) and Cu as the protective layer, there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 9.5% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 1290 μV and 1330 μV, respectively. 
     (2) In the case where a three-layered film is used for the non-magnetic layer: 
     When a spin valve film was produced using glass as the substrate, Si 3  N 4  as the buffer layer (80 nm), a 16-layered film of (NiFe (1 nm)/FeSiAl (1 nm))×8 as the first magnetic layer, a three-layered film of Ag (1 nm)/Cu (1 nm)/Ag (1 nm) as the non-magnetic layer, a 16-layered film of (FeNi (1 nm)/FeSiAl (1 nm))×8 as the second magnetic layer, FeMn as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of le and the rate of change of magnetoresistance of 9.5% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 1270 μV and 1310 μV, respectively. 
     EXAMPLE 19 
     In the structure shown in FIG. 1, the antiferromagnetic layers were formed under the conditions of (1) and (2) given below. The inverted magnetic field and the rate of change of the magnetoresistance of the second magnetic layer were measured. Also, the reproducing output value of the shield reproducing head and that of the yoke reproducing head were measured in the same manner as in Example 17. 
     (1) In the case where a double-layered film is used for the antiferromagnetic layer: 
     When a spin valve film was produced using glass as the substrate, Hf as the buffer layer (10 nm), NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), a double-layered film of NiO (10 nm)/CoO (10 nm) as the antiferromagnetic layer and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 7.5%. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 910 μV and 920 μV, respectively. 
     (2) In the case where a three-layered film is used for the antiferromagnetic layer: 
     When a spin valve film was produced using glass as the substrate, Hf as the buffer layer (10 nm), FeSiAl as the first magnetic layer (15 nm), Pt as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), a three-layered film of NiO (5 nm)/FeMn (5 nm)/NiO (5 nm) as the antiferromagnetic layer and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 20e and the rate of change of magnetoresistance of 8%. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 970 μV and 940 μV, respectively. 
     EXAMPLE 20 
     In the structure shown in FIG. 1, the buffer layers were formed under the conditions of (1) and (2) given below. The inverted magnetic field and the rate of change of the magnetoresistance of the second magnetic layer were measured. Also, the reproducing output value of the shield reproducing head and that of the yoke reproducing head were measured in the same manner as in Example 17. 
     (1) In the case where a double-layered film is used for the buffer layer: 
     When a spin valve film was produced using polycarbonate as the substrate, a double-layered film of Si 3  N 4  (50 nm)/Hf (10 nm) as the buffer layer, NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), a double-layered film of NiO (10 nm)/CoO (10 nm) as the antiferromagnetic layer and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 8% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 980 μV and 960 μV, respectively. 
     (2) When a three-layered film is used for the buffer layer: 
     When a spin valve film was produced using polycarbonate as the substrate, a three-layered film of Si 3  N 4  (50 nm)/Hf (5 nm)/Ta (5 nm) as the buffer layer, NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), a double-layered film of NiO (10 nm)/CoO (10 nm) as the antiferromagnetic layer and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 9% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 1260 μV and 1290 μV, respectively. 
     EXAMPLE 21 
     In the structure shown in FIG. 1, the protective layers were formed under the conditions of (1) and (2) given below. The inverted magnetic field and the rate of change of the magnetoresistance of the second magnetic layer were measured. Also, the reproducing output value of the shield reproducing head and that of the yoke reproducing head were measured in the same manner as in Example 17. 
     (1) In the case where a double-layered film is used for the protective layer: 
     When a spin valve film was produced using glass as the substrate, a double-layered film of Si 3  N 4  (50 nm)/Hf (10 nm) as the buffer layer, Cu as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and a double-layered film of Cu (2 nm)/Si 3  N 4  (50 nm) as the protective layer, there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 8% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 970 μV and 950 μV, respectively. 
     (2) When a three-layered film is used for the protective layer: 
     When a spin valve film was produced using glass as the substrate, a double-layered film of Si 3  N 4  (50 nm)/Hf (10 nm) as the buffer layer, NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), FeMn as the antiferromagnetic layer (15 nm) and a three-layered film of Cu (2 nm)/Si 3  N 4  (50 nm)/ an ultraviolet-curing resin (500 nm) as the protective layer, there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 8% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 950 μV and 950 μV, respectively. 
     EXAMPLE 22 
     In the structure shown in FIG. 1, the substrates of the following conditions (1) and (2) were used to measure the inverted magnetic field and the rate of change of the magnetoresistance of the second magnetic layer. Also, the reproducing output value of the shield reproducing head and that of the yoke reproducing head were measured in the same manner as in Example 17. 
     (1) In the case where a double-layered substrate is used: 
     When a spin valve film was produced using glass/SiO 2  as the substrate, Hf as the buffer layer (10 nm), NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 7% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 920 μV and 950 μV, respectively. 
     (2) In the case where another double-layered substrate is used: 
     When a spin valve film was produced using glass/UV-curing resin as the substrate, a double-layered film of SiO 2  (70 nm)/Hf (10 nm) as the buffer layer, NiFe as the first magnetic layer (15 nm), Cu as the non-magnetic layer (3 nm), FeNi as the second magnetic layer (15 nm), NiO as the antiferromagnetic layer (15 nm) and Cu as the protective layer (2 nm), there were obtained the inverted magnetic field of 10e and the rate of change of magnetoresistance of 7% of the second magnetic layer. The reproducing output value of the shield reproducing head and that of the yoke reproducing head were 940 μV and 910 μV, respectively. 
     As described above, according to the application of the present invention, a thin film having a good sensitivity with respect to magnetic field and a significant magnetoresistive effect can be obtained. When using this thin film for a shield reproducing head or a yoke reproducing head, the maximum reproducing output obtainable is approximately four times that of a reproducing head which utilizes the magnetoresistive effect provided by the application of the prior art. 
     
          TABLE 1!______________________________________            Second            magnetic        Shield            layer           head            inverted Rate of                            repro-                                  Yoke headFirst   Second   magnetic change in                            ducing                                  reproduc-magnetic   magnetic field    magneto-                            output                                  ing outputlayer   layer    (Oe)     resistance                            (μV)                                  (μV)______________________________________CoZrNb  CoZrNb   1        4      800   740CoZrMo  CoZrMo   1        3.5    730   690FeSiAl  FeSiAl   2        5      940   920FeSi    FeSi     10       5      570   490NiFe    NiFe     2        4      770   730NiFe    FeSiAl   2        5      980   910FeSiAl  NiFe     2        4      790   770NiFe    CoZrNb   1        4      880   810FeSiAl  CoZrNb   3        4      760   720CoZrNb  CoZrMo   1        4.5    1050  970______________________________________ 
    
     
          TABLE 2!______________________________________            Second            magnetic        Shield            layer           head            inverted Rate of                            repro-                                  Yoke headFirst   Second   magnetic change in                            ducing                                  reproduc-magnetic   magnetic field    magneto-                            output                                  ing outputlayer   layer    (Oe)     resistance                            (μV)                                  (μV)______________________________________CoZrNb  CoZrNb   2        5      930   860COZrMo  CoZrMo   1        3.5    810   670FeSiAl  FeSiAl   3        6      1070  980FeSi    FeSi     9        5      670   570NiFe    NiFe     2        4.5    820   770NiFe    FeSiAl   3        4.5    970   920FeSiAl  NiFe     1        4      870   810NiFe    CoZrNb   2        4      870   820FeSiAl  CoZrNb   4        5      790   790CoZrNb  CoZrMo   2        4.5    1070  1060______________________________________ 
    
     
          TABLE 3!______________________________________            Second            magnetic        Shield            layer           head            inverted Rate of                            repro-                                  Yoke headFirst   Second   magnetic change in                            ducing                                  reproduc-magnetic   magnetic field    magneto-                            output                                  ing outputlayer   layer    (Oe)     resistance                            (μV)                                  (μV)______________________________________CoZrNb  CoZrNb   1        4      870   900CoZrMo  CoZrMo   1        3      800   820FeSiAl  FeSiAl   2        7      900   930FeSi    FeSi     10       5      650   670NiFe    NiFe     2        4      790   810NiFe    FeSiAl   1        4      930   990FeSiAl  NiFe     1        4.5    880   940NiFe    CoZrNb   1        3.5    870   870FeSiAl  CoZrNb   3        4      810   860CoZrNb  CoZrMo   1        4      990   1070______________________________________ 
    
     
          TABLE 4!______________________________________     Second     magnetic            Shield     layer               head     inverted Rate of    repro-                               Yoke headNon-      magnetic change in  ducing                               reproduc-magnetic  field    magneto-   output                               ing outputlayer     (Oe)     resistance (μV)                               (μV)______________________________________Cu        1        5          990   1040Al        2        4.5        910   1000Si        4        3.5        810   880Ti        3        5          850   880V         3.5      4          790   850Zn        7        3.5        680   690Zr        1        4.5        880   990Nb        10       2          330   380Mo        3        5.5        910   900Pd        2        4.5        930   940Ag        1        6          1100  1130Sn        5        4          810   860Hf        2        5          860   920Ir        1        7          1120  1150Ta        1        4.5        900   890W         2        4          890   910Pt        1        5          960   990Au        1        7          1270  1330Pb        10       3          290   310Bi        20       3.5        220   230C         9        2          270   300SiC       7        2.5        260   270______________________________________ 
    
     
          TABLE 5!______________________________________     Second     magnetic            Shield     layer               head     inverted Rate of    repro-                               Yoke headNon-      magnetic change in  ducing                               reproduc-magnetic  field    magneto-   output                               ing outputlayer     (Oe)     resistance (μV)                               (μV)______________________________________Cu        3        4          550   590Al        4        3.5        670   660Si        5        3          470   460Ti        7        4          460   420V         8        3          390   420Zn        17       3          260   280Zr        6        3.5        460   490Nb        25       2.5        170   190Mo        6        5          670   660Pd        4        4          720   690Ag        3        5          820   870Sn        6        3          680   750Hf        7        4          620   690Ta        4        5.5        860   870W         6        4          790   810Pt        2        4.5        810   910Au        5        5          760   750Pb        16       2.5        280   280Bi        30       3          140   190C         12       2.5        160   210SiC       7        2.5        280   330______________________________________ 
    
     
          TABLE 6!______________________________________      Second      magnetic            Shield      layer               head      inverted Rate of    repro-                                Yoke headAntiferro- magnetic change in  ducing                                reproduc-magnetic   field    magneto-   output                                ing outputlayer      (Oe)     resistance (μV)                                (μV)______________________________________FeMn       1        5          880   930NiO        4        4.5        770   790NiO + CoO  3        4.5        790   830NiO + FeO  3        4          820   880Fe.sub.2 O.sub.3      6        3          380   390MnO        4        4          760   850CrO        1        6.5        920   960Cr         3        2.5        460   400Mn         5        3          490   520______________________________________ 
    
     
          TABLE 7!______________________________________      Second      magnetic            Shield      layer               head      inverted Rate of    repro-                                Yoke headAntiferro- magnetic change in  ducing                                reproduc-magnetic   field    magneto-   output                                ing outputlayer      (Oe)     resistance (μV)                                (μV)______________________________________FeMn       2        6          830   800NiO        3        5.5        810   790NiO + CoO  2        4.5        770   810NiO + FeO  4        4          680   760Fe.sub.2 O.sub.3      10       4          480   450MnO        3        4.5        620   600CrO        2        5.5        940   930Cr         4        3.5        570   490Mn         7        3.5        470   530______________________________________ 
    
     
          TABLE 8!______________________________________     Second     magnetic            ShieldElement   layer               headadded to  inverted Rate of    repro-                               Yoke headantiferro-     magnetic change in  ducing                               reproduc-magnetic  field    magneto-   output                               ing outputlayer     (Oe)     resistance (μV)                               (μV)______________________________________Mo        2        5          730   780W         3        5.5        820   790V         3        4.5        680   740Nb        1        5          990   1020Ta        4        4          680   690Ir        1        6          1030  1070Mn        3        4.5        760   750Tc        2        5.5        870   990Re        1        4.5        800   780Ru        3        5          820   790Rh        2        5          820   770Fe        2        5.5        810   760Co        1        6          960   1080Ni        3        4.5        720   740Pt        2        5.5        840   900Pd        3        4.5        780   810Au        2        5          860   820Ag        1        5          1000  1120Cu        1        6          1270  1340______________________________________ 
    
     
          TABLE 9!______________________________________     Second     magnetic            ShieldElement   layer               headadded to  inverted Rate of    repro-                               Yoke headantiferro-     magnetic change in  ducing                               reproduc-magnetic  field    magneto-   output                               ing outputlayer     (Oe)     resistance (μV)                               (μV)______________________________________Mo        3        5.5        780   840W         2        5.5        820   780V         3        5          740   790Ir        2        6          890   930Nb        2        6          890   1030Ta        3        6          870   990Mn        2        5.5        850   950Tc        4        6.5        930   1040Re        2        5.5        900   1050Ru        3        5          810   800Rh        2        6          860   840Fe        3        5.5        780   800Co        2        5          810   790Ni        2        4.5        760   760Pt        3        5.5        830   840Pd        2        5          770   840Au        3        5          770   830Ag        1        6          1100  1110Cu        2        6.5        1110  1170______________________________________ 
    
     
          TABLE 10!______________________________________     Second     magnetic            Shield     layer               head     inverted Rate of    repro-                               Yoke head     magnetic change in  ducing                               reproduc-Buffer    field    magneto-   output                               ing outputlayer     (Oe)     resistance (μV)                               (μV)______________________________________Ta        2        5          780   750Hf        3        4.5        770   730Si        7        3          510   490Au        4        2          190   180Pt        8        3          350   360Ag        4        4          670   730Cu        8        3.5        470   550Ti        17       2.5        370   400Mn        13       3.5        320   330Cr        14       3          360   390Al        5        4          680   660Si.sub.3 N.sub.4     2        6          820   930SiO.sub.2 3        6          840   940Al.sub.2 O.sub.3     2        6.5        910   970SiC       3        6          870   920C         10       2.5        250   290Diamond-  3        6          910   970likecarbon______________________________________ TABLE 11!______________________________________     Second     magnetic            Shield     layer               head     inverted Rate of    repro-                               Yoke head     magnetic change in  ducing                               reproduc-Buffer    field    magneto-   output                               ing outputlayer     (Oe)     resistance (μV)                               (μV)______________________________________Ta        1        5.5        820   860Hf        2        5          810   770Si        18       3.5        260   310Au        3        4          720   760Pt        3        6          820   900Ag        4        6.5        860   890Cu        11       3.5        370   350Ti        15       3          220   270Mn        14       3.5        280   320Cr        19       2          170   190Al        5        6          780   820Si.sub.3 N.sub.4     2        7          1030  1080SiO.sub.2 3        7          1020  1100Al.sub.2 O.sub.3     2        6.5        1010  1110SiC       2        7          990   1100C         12       2.5        220   290Diamond-  3        6.5        960   1090likecarbon______________________________________ TABLE 12!______________________________________             Second   Rate of                             Shield                                   Yoke             magnetic change head  head             layer    in     repro-                                   repro-    Thick-   inverted magneto-                             ducing                                   ducingProtective    ness     magnetic resist-                             output                                   outputlayer    (nm)     field (Oe)                      ance (%)                             (μV)                                   (μV)______________________________________Ta       3        2        5      820   840Hf       3        3        5.5    810   850Si       40       3        5      850   860Au       2        2        5      840   880Pt       2        2        5.5    810   870Ag       2        2        6      830   880Cu       2        2        6      850   900Ti       3        3        5.5    830   850Cr       3        3        5      840   840Al       3        2        5.5    830   860Si.sub.3 N.sub.4    50       2        6      820   930SiO.sub.2    80       3        6      840   940Al.sub.2 O.sub.3    60       2        6.5    910   970SiC      20       3        6      870   920C        30       4        5.5    780   810Diamond-like    20       3        6.5    830   880carbonCuTi     3        2        6      840   850CuPt     3        2        6      810   860TaTi     3        2        6.5    820   880PtAu     3        2        6.5    830   880AgAu     2        2        6      820   860CuCr     3        3        6      810   870Si oxide +    60       2        6.5    820   890Al oxideSi nitride +    50       2        6      830   860Al nitrideSi nitride +    60       2        6.5    840   890Si oxideAl nitride +    80       3        6.5    820   870Al oxideSi oxide +    50       2        6.5    840   900Si nitrideAl oxideAl nitride______________________________________ TABLE 13!______________________________________             Second   Rate of                             Shield                                   Yoke             magnetic change head  head             layer    in     repro-                                   repro-    Thick-   inverted magneto-                             ducing                                   ducingProtective    ness     magnetic resist-                             output                                   outputlayer    (nm)     field (Oe)                      ance (%)                             (μV)                                   (μV)______________________________________Ta       3        2        6      920   970Hf       3        2        7      1020  1070Si       40       3        6.5    950   1020Au       2        2        6.5    970   1110Pt       2        2        7      1030  1090Ag       2        3        6.5    900   910Cu       2        2        7      1090  1130Ti       3        3        6.5    930   940Cr       3        3        6.5    940   970Al       3        2        6      910   960Si.sub.3 N.sub.4    50       2        7      960   1130SiO.sub.2    80       2        7      990   1170Al.sub.2 O.sub.3    60       3        6.5    910   960SiC      20       2        7      1100  1180C        30       5        6      720   750Diamond-like    20       2        7      900   910carbonCuTi     3        3        6.5    930   970CuPt     3        2        6.5    910   980TaTi     3        3        6      890   950PtAu     3        2        7      910   960AgAu     2        2        7      920   990CuCr     3        3        6.5    820   860Si oxide +    60       2        7      940   960Al oxideSi nitride +    50       2        7      940   970Al nitrideSi nitride +    60       2        6.5    880   920Si oxideAl nitride +    80       2        6.5    870   870Al oxideSi oxide +    50       2        7      940   1040Si nitrideAl oxideAl nitride______________________________________ TABLE 14!______________________________________      Second   Rate of    Shield      magnetic change     head      layer    in         repro-                                Yoke head      inverted magneto-   ducing                                reproduc-      magnetic resist-    output                                ing outputSubstrate  field (Oe)               ance (%)   (μV)                                (μV)______________________________________Glass      2        5.5        830   870SiO.sub.2  3        6          920   990Si.sub.3 N.sub.4      2        5.5        850   880AlN        2        7          1010  1130Al.sub.2 O.sub.3      2        6.5        910   940SiO.sub.2 + Si.sub.3 N.sub.4      3        6.5        930   970AlN + Al.sub.2 O.sub.3      2        6.5        940   970Si.sub.3 N.sub.4 + Al.sub.2 O.sub.3      3        7          990   1070Si.sub.3 N.sub.4 + AlN      2        6.5        910   950SiO.sub.2 + Al.sub.2 O.sub.3 +      3        7          940   1040Si.sub.3 N.sub.4 + AlNAi         2        7          680   650Cu         3        7.5        690   660W          2        7          850   830Ti         2        7          840   810Mo         2        7.5        880   810NiCr alloy 3        7          890   840Zn         2        7          880   850CuZn alloy 2        7          860   830TiAl alloy 2        6.5        780   780Polycarbonate      8        4.5        430   470Vinyl      14       4          380   390chloridePolyimide  5        5          760   790Polyolefin 7        4.5        510   550Polycarbonate +      6        5.5        680   720polyolefin______________________________________ TABLE 15!______________________________________      Second   Rate of    Shield      magnetic change     head      layer    in         repro-                                Yoke head      inverted magneto-   ducing                                reproduc-      magnetic resist-    output                                ing outputSubstrate  field (Oe)               ance (%)   (μV)                                (μV)______________________________________Glass      2        6.5        820   860SiO.sub.2  2        7          960   980Si.sub.3 N.sub.4      3        6.5        790   810AlN        2        7.5        950   980Al.sub.2 O.sub.3      3        7          970   1040SiO.sub.2 + Si.sub.3 N.sub.4      2        7          970   1030AlN + Al.sub.2 O.sub.3      2        7          940   1010Si.sub.3 O.sub.2 + Al.sub.2 O.sub.3      3        7.5        980   1090Si.sub.3 N.sub.4 + AlN      2        7          920   940SiO.sub.2 + Al.sub.2 O.sub.3 +      2        7.5        1010  1040Si.sub.3 N.sub.4 + AlNAl         2        8          920   990Cu         3        7.5        910   1010W          2        7          890   930Ti         2        7.5        930   1030Mo         3        7          900   960NiCr alloy 3        7          890   960Zn         2        6.5        810   850CuZn alloy 2        7          870   910TiAl alloy 2        7          920   960Polycarbonate      5        6          630   680Vinyl      8        5          580   610chloridePolyimide  3        6          770   780Polyolefin 5        5          610   680Polycarbonate +      6        6          710   760polyolefin______________________________________ TABLE 16!______________________________________Film thickness of         Shield head  Yoke headfirst magnetic layer         reproducing output                      reproducing output(nm)          (μV)      (μV)______________________________________0             0            05             590          47010            900          78015            920          85020            890          86025            850          84030            820          80035            710          75040            600          68045            470          570______________________________________ 
    
     
          TABLE 17!______________________________________Film thickness of         Shield head  Yoke headfirst magnetic layer         reproducing output                      reproducing output(nm)          (μV)      (μV)______________________________________0             0            05             420          38010            750          69015            880          79020            960          86025            880          85030            810          81035            680          75040            510          65045            360          520______________________________________ 
    
     
          TABLE 18!______________________________________Film thickness of         Shield head  Yoke headfirst magnetic layer         reproducing output                      reproducing output(nm)          (μV)      (μV)______________________________________0             0            05             470          42010            770          72015            920          88020            910          95025            850          87030            720          81035            600          74040            440          65045            210          470______________________________________ 
    
     
          TABLE 19!______________________________________Film thickness of         Shield head  Yoke headsecond magnetic         reproducing output                      reproducing outputlayer (nm)    (μV)      (μV)______________________________________0             0            05             690          56010            880          74015            900          96020            780          82025            690          72030            560          60035            410          48040            260          32045            190          220______________________________________ 
    
     
          TABLE 20!______________________________________Film thickness of         Shield head  Yoke headnonmagnetic layer         reproducing output                      reproducing output(nm)          (μV)      (μV)______________________________________0             0            00.5           0            01.0           0            01.5           260          3002.0           780          8102.5           880          8903.0           920          9303.5           890          8804.0           740          7704.5           690          6505.0           520          510______________________________________ 
    
     
          TABLE 21!______________________________________Film thickness of         Shield head  Yoke headnonmagnetic layer         reproducing output                      reproducing output(nm)          (μV)      (μV)______________________________________0             0            00.5           0            01.0           0            01.5           320          3302.0           750          7902.5           840          8803.0           930          9503.5           870          8404.0           760          7204.5           640          6005.0           490          470______________________________________ 
    
     
          TABLE 22!______________________________________Film thickness of         Shield head  Yoke headantiferromagnetic         reproducing output                      reproducing outputlayer (nm)    (μV)      (μV)______________________________________0             0            010            880          89020            900          89050            870          860100           850          840200           830          810500           780          7601000          720          730______________________________________ 
    
     
          TABLE 23!______________________________________Film thickness of         Shield head  Yoke headantiferromagnetic         reproducing output                      reproducing outputlayer (nm)    (μV)      (μV)______________________________________0             0            010            780          77020            840          86050            870          880100           840          850200           820          820500           800          7901000          780          750______________________________________ 
    
     
          TABLE 24!______________________________________Film thickness of Cu        Shield head  Yoke headprotective layer        reproducing output                     reproducing output(nm)         (μV)      (μV)______________________________________0            920          9400.5          910          9501.0          920          9301.5          900          9002.0          900          9202.5          890          9103.0          850          8803.5          820          8404.0          760          7904.5          720          7505.0          680          690______________________________________ 
    
     
          TABLE 25!______________________________________Film thickness of        Shield head  Yoke headAgTi alloy protective        reproducing output                     reproducing outputlayer (nm)   (μV)      (μV)______________________________________0            970          9300.5          960          9501.0          960          9401.5          940          9202.0          950          9002.5          920          9103.0          920          8703.5          880          8104.0          790          7604.5          710          7105.0          650          630______________________________________ 
    
     
          TABLE 26!______________________________________Film thickness of        Shield head  Yoke headSi.sub.3 N.sub.4 protective layer        reproducing output                     reproducing output(nm)         (μV)      (μV)______________________________________0            920          9401            910          9502            920          9305            900          94010           920          92020           910          95050           920          950100          920          940______________________________________ 
    
     
          TABLE 27!______________________________________Film thickness of        Shield head  Yoke headAl.sub.2 O.sub.3 protective layer        reproducing output                     reproducing output(nm)         (μV)      (μV)______________________________________0            930          9401            940          9402            930          9505            940          93010           920          92020           940          94050           920          930100          930          920______________________________________ 
    
     
          TABLE 28!______________________________________Film thickness of         Shield head  Yoke headCuPtAuAg alloy buffer         reproducing output                      reproducing outputlayer (nm)    (μV)      (μV)______________________________________0             920          9505             910          94010            910          94015            890          92020            860          85025            810          81030            760          72035            700          660______________________________________ 
    
     
          TABLE 29!______________________________________Film thickness of Ta         Shield head  Yoke headalloy buffer layer         reproducing output                      reproducing output(nm)          (μV)      (μV)______________________________________0             850          8705             840          84010            830          84015            810          80020            780          75025            740          72030            690          68035            640          630______________________________________ 
    
     
          TABLE 30!______________________________________Film thickness of        Shield head  Yoke headSi.sub.3 N.sub.4 buffer layer        reproducing output                     reproducing output(nm)         (μV)      (μV)______________________________________0            780          7905            820          83010           850          86015           880          89020           890          89025           910          91030           900          90035           890          890______________________________________ 
    
     
          TABLE 31!______________________________________Film thickness of        Shield head  Yoke headbuffer layer reproducing output                     reproducing output(nm)         (μV)      (μV)______________________________________0            740          7605            830          84010           860          87015           850          86020           870          89025           860          88030           880          87035           860          890______________________________________