Spin valve film

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: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a magnetic head which utilizes the magnetoresistive effect. 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. Patent 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. Patent No. 4,949,039. For the spin valve film, the fundamental conception is also disclosed in U.S. Patent No. 5,206,590. In this disclosure, as materials forming each layer of the spin valve film, Co, Fe, Ni, NiFe, NiFe 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 good 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 obtaining 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 contrary, 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 contrary, 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 than 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 second 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) In the case where Hf is used for the 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 µm 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)) x 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)) x 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)) x 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)) x 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)) x 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)) x 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)) x 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)) x 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 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. According to the invention a spin valve film is disclosed 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. First magnetic layer Second magnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) CoZrNb CoZrNb 1 4 800 740 CoZrMo CoZrMo 1 3.5 730 690 FeSiAl FeSiAl 2 5 940 920 FeSi FeSi 10 5 570 490 NiFe NiFe 2 4 770 730 NiFe FeSiAl 2 5 980 910 FeSiAl NiFe 2 4 790 770 NiFe CoZrNb 1 4 880 810 FeSiAl CoZrNb 3 4 760 720 CoZrNb CoZrMo 1 4.5 1050 970 First magnetic layer Second magnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) CoZrNb CoZrNb 2 5 930 860 CoZrMo CoZrMo 1 3.5 810 670 FeSiAl FeSiAl 3 6 1070 980 FeSi FeSi 9 5 670 570 NiFe NiFe 2 4.5 820 770 NiFe FeSiAl 3 4.5 970 920 FeSiAl NiFe 1 4 870 810 NiFe CoZrNb 2 4 870 820 FeSiAl CoZrNb 4 5 790 790 CoZrNb CoZrMo 2 4.5 1070 1060 First magnetic layer Second magnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) CoZrNb CoZrNb 1 4 870 900 CoZrMo CoZrMo 1 3 800 820 FeSiAl FeSiAl 2 7 900 930 FeSi FeSi 10 5 650 670 NiFe NiFe 2 4 790 810 NiFe FeSiAl 1 4 930 990 FeSiAl NiFe 1 4.5 880 940 NiFe CoZrNb 1 3.5 870 870 FeSiAl CoZrNb 3 4 810 860 CoZrNb CoZrMo 1 4 990 1070 Non-magnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) Cu 1 5 990 1040 Al 2 4.5 910 1000 Si 4 3.5 810 880 Ti 3 5 850 880 V 3.5 4 790 850 Zn 7 3.5 680 690 Zr 1 4.5 880 990 Nb 10 2 330 380 Mo 3 5.5 910 900 Pd 2 4.5 930 940 Ag 1 6 1100 1130 Sn 5 4 810 860 Hf 2 5 860 920 Ir 1 7 1120 1150 Ta 1 4.5 900 890 W 2 4 890 910 Pt 1 5 960 990 Au 1 7 1270 1330 Pb 10 3 290 310 Bi 20 3.5 220 230 C 9 2 270 300 SiC 7 2.5 260 270 Non-magnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) Cu 3 4 550 590 Al 4 3.5 670 660 Si 5 3 470 460 Ti 7 4 460 420 V 8 3 390 420 Zn 17 3 260 280 Zr 6 3.5 460 490 Nb 25 2.5 170 190 Mo 6 5 670 660 Pd 4 4 720 690 Ag 3 5 820 870 Sn 6 3 680 750 Hf 7 4 620 690 Ta 4 5.5 860 870 W 6 4 790 810 Pt 2 4.5 810 910 Au 5 5 760 750 Pb 16 2.5 280 280 Bi 30 3 140 190 C 12 2.5 160 210 SiC 7 2.5 280 330 Antiferromagnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) FeMn 1 5 880 930 NiO 4 4.5 770 790 NiO + CoO 3 4.5 790 830 NiO + FeO 3 4 820 880 Fe 2 O 3 6 3 380 390 MnO 4 4 760 850 CrO 1 6.5 920 960 Cr 3 2.5 460 400 Mn 5 3 490 520 Antiferromagnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) FeMn 2 6 830 800 NiO 3 5.5 810 790 NiO + CoO 2 4.5 770 810 NiO + FeO 4 4 680 760 Fe 2 O 3 10 4 480 450 MnO 3 4.5 620 600 CrO 2 5.5 940 930 Cr 4 3.5 570 490 Mn 7 3.5 470 530 Element added to antiferromagnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) Mo 2 5 730 780 W 3 5.5 820 790 V 3 4.5 680 740 Nb 1 5 990 1020 Ta 4 4 680 690 Ir 1 6 1030 1070 Mn 3 4.5 760 750 Tc 2 5.5 870 990 Re 1 4.5 800 780 Ru 3 5 820 790 Rh 2 5 820 770 Fe 2 5.5 810 760 Co 1 6 960 1080 Ni 3 4.5 720 740 Pt 2 5.5 840 900 Pd 3 4.5 780 810 Au 2 5 860 820 Ag 1 5 1000 1120 Cu 1 6 1270 1340 Element added to antiferromagnetic layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) Mo 3 5.5 780 840 W 2 5.5 820 780 V 3 5 740 790 Ir 2 6 890 930 Nb 2 6 890 1030 Ta 3 6 870 990 Mn 2 5.5 850 950 Tc 4 6.5 930 1040 Re 2 5.5 900 1050 Ru 3 5 810 800 Rh 2 6 860 840 Fe 3 5.5 780 800 Co 2 5 810 790 Ni 2 4.5 760 760 Pt 3 5.5 830 840 Pd 2 5 770 840 Au 3 5 770 830 Ag 1 6 1100 1110 Cu 2 6.5 1110 1170 Buffer layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) Ta 2 5 780 750 Hf 3 4.5 770 730 Si 7 3 510 490 Au 4 2 190 180 Pt 8 3 350 360 Ag 4 4 670 730 Cu 8 3.5 470 550 Ti 17 2.5 370 400 Mn 13 3.5 320 330 Cr 14 3 360 390 Al 5 4 680 660 Si 3 N 4 2 6 820 930 SiO 2 3 6 840 940 Al 2 O 3 2 6.5 910 970 SiC 3 6 870 920 C 10 2.5 250 290 Diamond-like carbon 3 6 910 970 Buffer layer Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance Shield head reproducing output (µV) Yoke head reproducing output (µV) Ta 1 5.5 820 860 Hf 2 5 810 770 Si 18 3.5 260 310 Au 3 4 720 760 Pt 3 6 820 900 Ag 4 6.5 860 890 Cu 11 3.5 370 350 Ti 15 3 220 270 Mn 14 3.5 280 320 Cr 19 2 170 190 Al 5 6 780 820 Si 3 N 4 2 7 1030 1080 SiO 2 3 7 1020 1100 Al 2 O 3 2 6.5 1010 1110 SiC 2 7 990 1100 C 12 2.5 220 290 Diamond-like carbon 3 6.5 960 1090 Protective layer Thickness (nm) Second magnetic layer inverted magnetic field (Oe) Rate of change in magneto-resistance (%) Shield head reproducing output (µV) Yoke head reproducing output (µV) Ta 3 2 5 820 840 Hf 3 3 5.5 810 850 Si 40 3 5 850 860 Au 2 2 5 840 880 Pt 2 2 5.5 810 870 Ag 2 2 6 830 880 Cu 2 2 6 850 900 Ti 3 3 5.5 830 850 Cr 3 3 5 840 840 Al 3 2 5.5 830 860 Si 3 N 4 50 2 6 820 930 SiO 2 80 3 6 840 940 Al 2 O 3 60 2 6.5 910 970 SiC 20 3 6 870 920 C 30 4 5.5 780 810 Diamond-like carbon 20 3 6.5 830 880 CuTi 3 2 6 840 850 CuPt 3 2 6 810 860 TaTi 3 2 6.5 820 880 PtAu 3 2 6.5 830 880 AgAu 2 2 6 820 860 CuCr 3 3 6 810 870 Si oxide + Al oxide 60 2 6.5 820 890 Si nitride + Al nitride 50 2 6 830 860 Si nitride + Si oxide 60 2 6.5 840 890 Al nitride + Al oxide 80 3 6.5 820 870 Si oxide + Si nitride + Al oxide + Al nitride 50 2 6.5 840 900 Protective layer Thickness (nm) Second magnetic layer inverted magnetic field (Oe) Rate of change in magneto-resistance (%) Shield head reproducing output (µV) Yoke head reproducing output (µV) Ta 3 2 6 920 970 Hf 3 2 7 1020 1070 Si 40 3 6.5 950 1020 Au 2 2 6.5 970 1110 Pt 2 2 7 1030 1090 Ag 2 3 6.5 900 910 Cu 2 2 7 1090 1130 Ti 3 3 6.5 930 940 Cr 3 3 6.5 940 970 Al 3 2 6 910 960 Si 3 N 4 50 2 7 960 1130 SiO 2 80 2 7 990 1170 Al 2 O 3 60 3 6.5 910 960 SiC 20 2 7 1100 1180 C 30 5 6 720 750 Diamond-like carbon 20 2 7 900 910 CuTi 3 3 6.5 930 970 CuPt 3 2 6.5 910 980 TaTi 3 3 6 890 950 PtAu 3 2 7 910 960 AgAu 2 2 7 920 990 CuCr 3 3 6.5 820 860 Si oxide + Al oxide 60 2 7 940 960 Si nitride + Al nitride 50 2 7 940 970 Si nitride + Si oxide 60 2 6.5 880 920 Al nitride + Al oxide 80 2 6.5 870 870 Si oxide + Si nitride + Al oxide + Al nitride 50 2 7 940 1040 Substrate Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance (%) Shield head reproducing output (µV) Yoke head reproducing output (µV) Glass 2 5.5 830 870 SiO 2 3 6 920 990 Si 3 N 4 2 5.5 850 880 AlN 2 7 1010 1130 Al 2 O 3 2 6.5 910 940 SiO 2 + Si 3 N 4 3 6.5 930 970 AlN + Al 2 O 3 2 6.5 940 970 Si 3 N 4 + Al 2 O 3 3 7 990 1070 Si 3 N 4 + AlN 2 6.5 910 950 SiO 2 + Al 2 O 3 + Si 3 N 4 + AlN 3 7 940 1040 Al 2 7 680 650 Cu 3 7.5 690 660 W 2 7 850 830 Ti 2 7 840 810 Mo 2 7.5 880 810 NiCr alloy 3 7 890 840 Zn 2 7 880 850 CuZn alloy 2 7 860 830 TiAl alloy 2 6.5 780 780 Polycarbonate 8 4.5 430 470 Vinyl chloride 14 4 380 390 Polyimide 5 5 760 790 Polyolefin 7 4.5 510 550 Polycarbonate + polyolefin 6 5.5 680 720 Substrate Second magnetic layer inverted magnetic field (Oe) Rate of change in magnetoresistance (%) Shield head reproducing output (µV) Yoke head reproducing output (µV) Glass 2 6.5 820 860 SiO 2 2 7 960 980 Si 3 N 4 3 6.5 790 810 AlN 2 7.5 950 980 Al 2 O 3 3 7 970 1040 SiO 2 + Si 3 N 4 2 7 970 1030 AlN + Al 2 O 3 2 7 940 1010 Si 3 O 2 + Al 2 O 3 3 7.5 980 1090 Si 3 N 4 + AlN 2 7 920 940 SiO 2 + Al 2 O 3 + Si 3 N 4 + AlN 2 7.5 1010 1040 Al 2 8 920 990 Cu 3 7.5 910 1010 W 2 7 890 930 Ti 2 7.5 930 1030 Mo 3 7 900 960 NiCr alloy 3 7 890 960 Zn 2 6.5 810 850 CuZn alloy 2 7 870 910 TiAl alloy 2 7 920 960 Polycarbonate 5 6 630 680 Vinyl chloride 8 5 580 610 Polyimide 3 6 770 780 Polyolefin 5 5 610 680 Polycarbonate + polyolefin 6 6 710 760 Film thickness of first magnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 5 590 470 10 900 780 15 920 850 20 890 860 25 850 840 30 820 800 35 710 750 40 600 680 45 470 570 Film thickness of first magnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 5 420 380 10 750 690 15 880 790 20 960 860 25 880 850 30 810 810 35 680 750 40 510 650 45 360 520 Film thickness of first magnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 5 470 420 10 770 720 15 920 880 20 910 950 25 850 870 30 720 810 35 600 740 40 440 650 45 210 470 Film thickness of second magnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 5 690 560 10 880 740 15 900 960 20 780 820 25 690 720 30 560 600 35 410 480 40 260 320 45 190 220 Film thickness of nonmagnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 0.5 0 0 1.0 0 0 1.5 260 300 2.0 780 810 2.5 880 890 3.0 920 930 3.5 890 880 4.0 740 770 4.5 690 650 5.0 520 510 Film thickness of nonmagnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 0.5 0 0 1.0 0 0 1.5 320 330 2.0 750 790 2.5 840 880 3.0 930 950 3.5 870 840 4.0 760 720 4.5 640 600 5.0 490 470 Film thickness of antiferromagnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 10 880 890 20 900 890 50 870 860 100 850 840 200 830 810 500 780 760 1000 720 730 Film thickness of antiferromagnetic layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 0 0 10 780 770 20 840 860 50 870 880 100 840 850 200 820 820 500 800 790 1000 780 750 Film thickness of Cu protective layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 920 940 0.5 910 950 1.0 920 930 1.5 900 900 2.0 900 920 2.5 890 910 3.0 850 880 3.5 820 840 4.0 760 790 4.5 720 750 5.0 680 690 Film thickness of AgTi alloy protective layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 970 930 0.5 960 950 1.0 960 940 1.5 940 920 2.0 950 900 2.5 920 910 3.0 920 870 3.5 880 810 4.0 790 760 4.5 710 710 5.0 650 630 Film thickness of Si 3 N 4 protective layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 920 940 1 910 950 2 920 930 5 900 940 10 920 920 20 910 950 50 920 950 100 920 940 Film thickness of Al 2 O 3 protective layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 930 940 1 940 940 2 930 950 5 940 930 10 920 920 20 940 940 50 920 930 100 930 920 Film thickness of CuPtAuAg alloy buffer layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 920 950 5 910 940 10 910 940 15 890 920 20 860 850 25 810 810 30 760 720 35 700 660 Film thickness of Ta alloy buffer layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 850 870 5 840 840 10 830 840 15 810 800 20 780 750 25 740 720 30 690 680 35 640 630 Film thickness of Si 3 N 4 buffer layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 780 790 5 820 830 10 850 860 15 880 890 20 890 890 25 910 910 30 900 900 35 890 890 Film thickness of buffer layer (nm) Shield head reproducing output (µV) Yoke head reproducing output (µV) 0 740 760 5 830 840 10 860 870 15 850 860 20 870 890 25 860 880 30 880 870 35 860 890

Claims: A spin valve film comprising a first magnetic layer, a non-magnetic layer, a second magnetic layer, and an antiferromagnetic layer as the fundamental structure for the film, wherein a single-layered film or a multi-layered film consisting of CoZrNb, CoZrMo, FeSiAl or FeSi is used for at least one of said first magnetic layer and second magnetic layer. The spin valve film according to Claim 1, wherein 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 is used for said non-magnetic layer. The spin valve film according to Claim 1 or 2, wherein 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 or 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 used as said antiferromagnetic layer. The spin valve film according to any of Claims 1 to 3, wherein 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 is used for said first or second magnetic layer. A spin valve film comprising a first magnetic layer, a non-magnetic layer, a second magnetic layer, and an antiferromagnetic layer as the fundamental structure for the film, wherein at least one of said first magnetic layer and said second magnetic layer is formed of NiFe or NiFeCo, and 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 and silicon carbide or a mixture thereof is used for said non-magnetic layer. The spin valve film according to Claim 5, wherein a single substance selected from CoO, FeO, Fe 2 O 3 , MnO, CrO, Cr and Mn or a mixture thereof, or a single-layered film or a multi-layered film of 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 used as said antiferromagnetic layer. The spin valve film according to any of Claims 1 to 6, wherein said first magnetic layer or said antiferromagnetic layer is in contact with a substrate or a buffer layer formed on the substrate. The spin valve film according to Claim 7, wherein a protective layer is formed on the outermost layer. The spin valve film according to Claim 7 or 8, wherein at least one of said first magnetic layer and said second magnetic layer is formed of CoZrNb, CoZrMo, FeSiAl, FeSi, NiFe or NiFeCo, and a single-layered film or a multi-layered film formed of glass, ceramic, metal, metal compound or plastic or a mixture thereof is used for said substrate. The spin valve film according to any of Claims 7 to 9, wherein 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 is used for said buffer layer. The spin valve film according to any of Claims 8 to 10, wherein 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 thereof is used for said protective layer. The spin valve film according to any of Claims 1 to 11, wherein the film thickness of at least one of said first magnetic layer and said second magnetic layer is 5 to 30 nm. The spin valve film according to any of Claims 1 to 12, wherein the film thickness of said non-magnetic layer is 2 to 5 nm. The spin valve film according to any of Claims 1 to 13, wherein the film thickness of said antiferromagnetic layer is 10 to 100 nm. The spin valve film according to any of Claims 1 to 14, wherein the film thickness of a metallic protective layer is 3 nm or less. The spin valve film according to any of Claims 1 to 15, wherein the film thickness of a non-metallic protective layer is 2 nm or more. The spin valve film according to any of Claims 1 to 16, wherein the film thickness of a metallic buffer layer is 15 nm or less. The spin valve film according to any of Claims 1 to 17, wherein the film thickness of a non-metallic buffer layer is 5 nm or more.

Inventors: HAYASHI KAZUHIKO, HAYASHI, KAZUHIKO, HAYASHI, KAZUHIKO, C/O NEC CORP.
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1995
Main classification: G01R33
IPC codes: G11B5, H01L43, G01R33, H01F10