Magnetoresistive effect sensor, thin-film magnetic head with the sensor and manufacturing method of the thin-film magnetic head

A thin-film magnetic head having a spin valve effect multi-layered structure including a non-magnetic electrically conductive material layer, first and second ferromagnetic material layers separated by the non-magnetic electrically conductive material layer, and an anti-ferromagnetic material layer formed adjacent to and in physical contact with one surface of the second ferromagnetic material layer. This one surface is an opposite side from the non-magnetic electrically conductive material layer and the multi-layered structure has ends at its track-width direction. The head also has longitudinal bias means formed at both the track-width ends of the multi-layered structure, for providing a longitudinal magnetic bias to the multi-layered structure. The multi-layered structure and the longitudinal bias means are formed such that an angle between a direction of exchange coupling magnetic bias in the second ferromagnetic material layer produced by the exchange coupling with the anti-ferromagnetic material layer and a direction of the longitudinal magnetic bias in the second ferromagnetic material layer is more than 90.degree. in at least part of the second ferromagnetic material layer.

FIELD OF THE INVENTION
 The present invention relates to a magnetoresistive effect (MR) sensor
 especially using a giant magnetoresistive effect (GMR), such as spin valve
 effect, to a thin-film magnetic head with the MR sensor used in a HDD
 (Hard Disk Drive) unit for a computer, and to a manufacturing method of
 the thin-film magnetic head.
 DESCRIPTION OF THE RELATED ART
 Recent widespread use of personal computers has increased the popularity of
 network transmissions of digital information including for not only
 conventional numerical digital data but also digital image data. Thus, the
 amounts of information to be treated are dramatically increasing.
 In order to process such massive amounts of digital information, it is
 necessary to use fast microprocessor units (MPU) and fast and reliable HDD
 units with large capacity. To realize such HDD units, high sensitivity and
 large output magnetic heads are required.
 An anisotropic magnetoresistive effect (AMR) head utilizing an abnormal
 magnetoresistive effect of a ferromagnetic thin-film layer based upon
 so-called spin-orbit interaction, wherein electrical resistance of the
 ferromagnetic layer varies depending upon the electrical field, has been
 widely known. For example, IEEE Transaction on Magnetics, Vol. MAG-7, No.
 1, pp. 150-154, March 1971 discloses such an AMR head.
 A thin-film layer of NiFe, NiFeCo, FeCo or NiCo material usually forms the
 AMR sensor in such a head. However, the relative change in resistance
 .DELTA.R/R of the NiFe thin-film layer, which exhibits most excellent soft
 magnetic characteristics among these materials, is merely 2-3 % at most.
 Thus, it was necessary to develop MR material with a greater
 magnetoresistance.
 In order to satisfy the requirement for high sensitivity and high power
 magnetic heads, more recently, thin-film magnetic heads with MR sensors
 based on the spin valve effect of CMR characteristics have been proposed.
 For example, Physical Review B, Vol.43, No. 1, pp. 1297-1300, Jan. 1991,
 Journal of Applied Physics, Vol. 69, No. 8, pp. 4774-4779, Apr. 1991, IEEE
 Transaction on Magnetics, Vol. 30, No. 6, pp. 3801-3806, Nov. 1994, and
 U.S. Pat. Nos. 5,206,590 and 5,422,571 disclose these heads.
 The spin valve effect thin-film structure includes first and second
 thin-film layers of a ferromagnetic material magnetically separated by a
 thin-filmlayer of non-magnetic metallicmaterial, and an adjacent layer of
 anti-ferromagnetic material is formed in physical contact with the second
 ferromagnetic layer to provide an exchange bias magnetic field by exchange
 coupling at the interface of the layers. The magnetization direction in
 the second ferromagnetic layer is constrained or maintained by the
 exchange coupling, hereinafter the second layer is called the "pinned
 layer". On the other hand, the magnetization direction of the first
 ferromagnetic layer is free to rotate in response to an externally applied
 magnetic field, hereinafter, the first layer is called the "free layer".
 The direction of the magnetization in the free layer changes between
 parallel and anti-parallel against the direction of the magnetization in
 the pinned layer, and hence the magneto-resistance greatly changes and the
 GMR characteristics are obtained.
 The output characteristic of the spin valve effect MR sensor depends upon
 the angular difference of magnetization between the free and pinned
 ferromagnetic layers. The direction of the magnetization of the free layer
 is free to rotate in accordance with an external magnetic field. That of
 the pinned layer is theoretically fixed to a specific direction (referred
 to as "pinned direction") by the exchange coupling between this layer and
 an adjacently formed anti-ferromagnetic layer.
 In fact, the spin valve effect MR sensor for the magnetic read head is
 fabricated by patterning the multi-layered spin valve effect MR sensor in
 a rectangular shape, by providing to the free layer the axis of easy
 magnetization along the track-width direction (longitudinal direction),
 and by providing to the pinned layer the exchange coupling bias
 magnetization along the sensor-height direction (transverse direction)
 which is perpendicular to the track-width direction so that magnetization
 directions of the free and pinned layers are kept orthogonal to each other
 under no magnetic field environment.
 In this kind of spin valve effect MR sensor, the direction of the
 magnetization of the pinned layer may change or rotate by various reasons
 as follows.
 (1) In general, at both end portions in the track-width direction of the
 spin valve effect MR sensor, hard magnet layers are formed for providing
 the longitudinal bias for a static magnetic field to the free layer so as
 to prevent non-linear magnetization in the free layer and non-reciprocal
 change in magnetization, called Barkhausen noise, from occuring. However,
 this longitudinal magnetic bias is applied not only to the free layer but
 also to the pinned layer causing the magnetization direction of the pinned
 layer at its both end portions to change or rotate.
 (2) A sense current is applied to the spin valve effect MR sensor to flow
 toward a specific direction (against direction) to produce a magnetic
 field which will change the magnetization of the free layer to its
 longitudinal direction. However, since the magnetic field produced by the
 sense current does not have the same direction as the exchange coupling
 bias magnetization in the pinned layer, the magnetization direction of the
 pinned layer will change or rotate.
 (3) Furthermore, since the exchange magnetic bias produced between the
 pinned layer and the anti-ferromagnetic layer has temperature dependency,
 the applied exchange magnetic bias to the pinned layer will be reduced in
 magnitude when the temperature of the spin valve effect MR sensor
 increases. This reduction of the exchange coupling bias may build up the
 change or rotation of the magnetization direction of the pinned layer.
 If the direction of the magnetization changes, the angular difference
 between the pinned and free layers also changes and, therefore, the output
 characteristic also changes. Consequently, stabilizing the direction of
 the magnetization in the pinned layer is very important.
 SUMMARY OF THE INVENTION
 It is therefore an object of the present invention to resolve the
 aforementioned problems by using a new approach, and to provide an MR
 sensor, a thin-film magnetic head with the MR sensor and manufacturing
 method of the thin-film magnetic head, whereby improved output
 characteristics and an enlarged permissible temperature range can be
 expected.
 According to the present invention, pinned direction and its distribution
 are determined with consideration of the rotation of magnetization in the
 pinned layer.
 More particularly, a thin-film magnetic head according to the present
 invention has a spin valve effect multi-layered structure including a
 non-magnetic electrically conductive material layer, first and second
 ferromagnetic material layers (free and pinned layers) separated by the
 non-magnetic electrically conductive material layer, and an
 anti-ferromagnetic material layer formed adjacent to and in physical
 contact with one surface of the second ferromagnetic material layer. This
 one surface is an opposite side of the non-magnetic electrically
 conductive material layer. The multi-layered structure has ends at its
 track-width direction. The head also has longitudinal bias means formed at
 both the track-width ends of the multi-layered structure, for providing a
 longitudinal magnetic bias to the multi-layered structure. The
 multi-layered structure and the longitudinal bias means are formed such
 that an angle between a direction of exchange coupling magnetic bias in
 the second ferromagnetic material layer produced by the exchange coupling
 with the anti-ferromagnetic material layer and a direction of the
 longitudinal magnetic bias in the second ferromagnetic material layer (Hex
 angle) is more than 90.degree. in at least part of the second
 ferromagnetic material layer.
 The Hex angle, which is the angle between the direction of the exchange
 coupling magnetic bias applied to the pinned layer (pinned direction) and
 the longitudinal bias direction (reference direction), is set to an angle
 of more than 90.degree. at least part of the pinned layer. Thus, after the
 magnet magnetization process is executed, the angles .theta.p in the
 pinned layer become substantially 90.degree.
 (.theta.p.apprxeq.90.degree.). As a result, improved output
 characteristics, namely improved output wave shape and improved wave
 symmetry, and also enlarged permissible temperature range can be expected.
 In general, the pinned layer suffers influences of the longitudinal
 magnetic field Hhm, applied external magnetic field Happl, magnetic field
 induced by the sense current His and self-demagnetization magnetic field
 of the pinned layer Hdp other than the exchange coupling magnetic bias
 Hex. If the magnetization in the free layer is directed toward the
 longitudinal direction, the track-width of the spin valve effect
 multi-layered structure is greater than its height and the anisotropic
 magnetic field of the pinned layer Hk is small, the magnetization angle of
 the pinned layer .theta.p is given as follows:
EQU .theta.p=tan.sup.-1 {(Hex+Happl+His-0.5
 Hdp).multidot.tp/(Hhm.multidot.thm)}
 where tp is a thickness of the pinned layer and thm is a thickness of the
 longitudinal bias means.
 The applied external magnetic field Happl varies between a positive and a
 negative level and the sense current magnetic field His is typically a
 negative level (if positive, it will be up to 20 Oe at the sense current
 of 5 mA). Therefore, in order to control the magnetization angle of the
 pinned layer as .theta.p=90.degree., it is necessary to provide an
 exchange coupling magnetic bias Hex sufficiently greater than the
 longitudinal magnetic field Hhm, the applied external magnetic field
 Happl, the magnetic field induced by the sense current His and the
 self-demagnetization magnetic field of the pinned layer Hdp. However, the
 exchange coupling magnetic bias Hex will be typically 200-1000 Oe, whereas
 the longitudinal magnetic field Hhm is not negligible as 100-2000 Oe.
 Therefore, into the pinned layer, particularly to the areas near its
 track-width ends, a strong longitudinal magnetic bias is applied causing
 .theta.p to become an angle much smaller than 90.degree.. Also, .theta.p
 over the whole area of the pinned layer will become smaller than
 90.degree.. In addition, if the temperature of the spin valve effect
 multi-layered stricture increases, the exchange coupling magnetic bias Hex
 component of the anti-ferromagnetic material with a lower blocking
 temperature decreases, causing the pinned direction to incline toward the
 longitudinal bias direction and thus causing .theta.p to further decrease.
 However, according to the present invention, because the direction of the
 exchange coupling magnetic bias Hex is set to compensate for such a
 decrease of .theta.p, the finally composed .theta.p becomes substantially
 equal to 90.degree..
 It is preferred that the Hex angle is equal to or less than 130.degree.. It
 is also preferred that the Hex angle is more than 90.degree. over the
 whole area of the pinned layer.
 It is preferred that the Hex angle in both longitudinal end portions of the
 pinned layer is greater than the Hex angle in a center portion of the
 pinned layer. Preferably, this Hex angle is equal to or more than
 100.degree. and equal to or less than 140.degree. in both the longitudinal
 end portions of the pinned layer.
 According to the present invention, furthermore, a method of manufacturing
 a thin-film magnetic head has a step of forming a spin valve effect
 multi-layered structure including a non-magnetic electrically conductive
 material layer, first and second ferromagnetic material layers (free and
 pinned layers) separated by the non-magnetic electrically conductive
 material layer, and an anti-ferromagnetic material layer formed adjacent
 to and in physical contact with one surface of the second ferromagnetic
 material layer, the one surface being an opposite side of the non-magnetic
 electrically conductive material layer, the multi-layered structure having
 ends at its track-width direction, a step of forming longitudinal bias
 means at both the track-width ends of the multi-layered structure, the
 means providing a longitudinal magnetic bias to the multi-layered
 structure, and a step of annealing the multi-layered structure at a
 temperature equal to or less than the blocking temperature of the
 anti-ferromagnetic material layer under application of magnetic field to
 the multi-layered structure, for providing exchange coupling between the
 anti-ferromagnetic material layer and the second ferromagnetic material
 layer. The exchange coupling produces an exchange coupling magnetic bias
 in the second ferromagnetic material layer. An angle between a direction
 of the produced exchange coupling magnetic bias in the second
 ferromagnetic material layer and a direction of the longitudinal magnetic
 bias in the second ferromagnetic material layer is greater than
 90.degree..
 By executing the annealing step, the Hex angle, which is the angle between
 the direction of the exchange coupling magnetic bias applied to the pinned
 layer (pinned direction) and the longitudinal bias direction (reference
 direction) is set to an angle greater than 90.degree. at least part of the
 pinned layer. Thus, even if the longitudinal bias means is formed, the
 angles .theta.p between the directions of the finally composed
 magnetization and the reference direction under no magnetic field
 environment become substantially 90.degree.. In other words, the total
 angles .theta.p in the pinned layer becomes substantially 90.degree.
 (.theta.p=90.degree.). As a result, improved output characteristics,
 namely, improved output wave shape and improved wave symmetry, and also an
 enlarged permissible temperature range can be expected.
 It is preferred that the annealing step provides the exchange coupling
 between the anti-ferromagnetic material layer and the pinned layer so that
 the Hex angle is equal to or less than 130.degree..
 According to the present invention, also, a method of manufacturing a
 thin-film magnetic head has a step of forming a spin valve effect
 multi-layered structure including a non-magnetic electrically conductive
 material layer, first and second ferromagnetic material layers separated
 by the non-magnetic electrically conductive material layer, and an
 anti-ferromagnetic material layer formed adjacent to and in physical
 contact with one surface of the second ferromagnetic material layer, the
 one surface being an opposite side of the non-magnetic electrically
 conductive material layer, the multi-layered structure having ends at its
 track-width direction, a step of forming a longitudinal bias means at both
 the track-width ends of the multi-layered structure, for providing a
 longitudinal magnetic bias to the multi-layered structure, a step of
 magnetizing the longitudinal bias means toward in a direction opposite a
 reference direction for the longitudinal magnetic bias, a step of
 annealing the multi-layered structure at a temperature equal to or less
 than the blocking temperature of the anti-ferromagnetic material layer
 under application of magnetic field in a direction perpendicular to the
 reference direction for the longitudinal magnetic bias to the
 multi-layered structure, for producing exchange coupling between the
 anti-ferromagnetic material layer and the second ferromagnetic material
 layer, the exchange coupling producing exchange coupling magnetic bias in
 the second ferromagnetic material layer, and a step of magnetizing again
 the longitudinal bias means toward the reference direction for the
 longitudinal magnetic bias.
 Since the longitudinal bias means are magnetized toward the opposite to a
 reference direction for the longitudinal magnetic bias and thereafter an
 annealing step for providing the exchange coupling between the
 anti-ferromagnetic material layer and the pinned layer to produce exchange
 coupling magnetic bias in this pinned layer, the Hex angle in both
 longitudinal end portions of the pinned layer becomes more than 90.degree.
 and the Hex angle in a center portion of the pinned layer becomes about
 90.degree.. In other words, during the annealing process, in the
 longitudinal end portions of the pinned layer, the longitudinal magnetic
 bias Hhm operates causing the Hex angle of the composed exchange coupling
 bias to become more than 90.degree.. Thus, after again the longitudinal
 bias means is magnetized again toward the normal direction, the angles
 .theta.p between the directions of the finally composed magnetization and
 the reference direction under no magnetic field environment become
 substantially 90.degree.. In other words, the total angles .theta.p over
 the whole area in the pinned layer become substantially 90.degree.
 (.theta.p.apprxeq.90.degree.). As a result, improved output
 characteristics, namely improved output wave shape and improved wave
 symmetry, and also an enlarged permissible temperature range can be
 expected.
 It is preferred that the annealing step provides the exchange coupling
 between the anti-ferromagnetic material layer and the pinned layer so that
 the Hex angle is equal to or more than 100.degree. and equal to or less
 than 140.degree. in both the longitudinal end portions of the pinned
 layer.
 It is also preferred that the method further has a step of controlling
 anisotropy of the free layer, executed before the annealing step.
 According to the present invention, furthermore, a MR sensor has a magnetic
 multi-layered structure including a non-magnetic electrically conductive
 material layer, first and second ferromagnetic material layers separated
 by the non-magnetic electrically conductive material layer, and an
 anti-ferromagnetic material layer formed adjacent to and in physical
 contact with one surface of the second ferromagnetic material layer. This
 one surface is an opposite side of the non-magnetic electrically
 conductive material layer. The multi-layered structure is formed such that
 an angle between a direction of exchange coupling magnetic bias in the
 second ferromagnetic material layer produced by the exchange coupling with
 the anti-ferromagnetic material layer and a magnetically sensitive surface
 direction of the magnetoresistive effect sensor is more than 90.degree. in
 at least part of the second ferromagnetic material layer.
 Also, according to the present invention, a thin-film magnetic head has a
 magnetic multi-layered structure including a non-magnetic electrically
 conductive material layer, first and second ferromagnetic material layers
 separated by the non-magnetic electrically conductive material layer, and
 an anti-ferromagnetic material layer formed adjacent to and in physical
 contact with one surface of the second ferromagnetic material layer. This
 one surface is an opposite side of the non-magnetic electrically
 conductive material layer. The multi-layered structure is formed such that
 an angle between a direction of exchange coupling magnetic bias in the
 second ferromagnetic material layer produced by the exchange coupling with
 the anti-ferromagnetic material layer and a track-width direction of the
 thin-film magnetic head is more than 90.degree. in at least part of the
 second ferromagnetic material layer.
 Further objects and advantages of the present invention will be apparent
 from the following description of the preferred embodiments of the
 invention as illustrated in the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIG. 1 illustrates a spin valve effect multi-layered structure and hard
 magnet layers for producing longitudinal magnetic bias of a spin valve
 effect Mr sensor of a thin-film magnetic head. Referring to FIG. 1,
 reference numerals 10 and 12 denote first and second ferromagnetic
 thin-film layers, respectively, which are magnetically separated by a
 thin-film layer 11 of a non-magnetic electrically conductive material. On
 the second ferromagnetic thin-film layer 12, a thin-film layer 13 of
 anti-ferromagnetic material is stacked, and a magnetic field generated by
 the exchange coupling at the interface of the thin-film layers 12 and 13
 magnetizes the ferromagnetic layer 12, and, so to speak, the layer is
 pinned. Thus, the second ferromagnetic layer 12 is referred to as a pinned
 layer. The first ferromagnetic thin-film layer 10 is a free layer in which
 there is no effect of exchange coupling and hence the magnetization is
 free to rotate in response to an externally applied magnetic field. In
 FIG. 1, furthermore, reference numerals 14 and 15 denote hard magnet
 layers formed to contact with the both end portions in the track-width
 direction of the spin valve effect multi-layered structure 16 for
 providing longitudinal magnetic bias toward one direction to the free
 layer 10 of the multi-layered structure 16. Stacked structures of
 anti-ferromagnetic material layers and ferromagnetic material layers may
 be used for providing the longitudinal magnetic bias instead of the
 permanent magnet layers 14 and 15. Thus, the second ferromagnetic layer 12
 is called as a pinned layer. The first ferromagnetic thin-film layer 10 is
 a free layer in which there is no effect of exchange coupling and hence
 the magnetization is free to rotate in response to an externally applied
 magnetic field. In FIG. 1, furthermore, reference numerals 14 and 15
 denote hard magnet layers formed to contact with the both end portions in
 the track-width direction of the spin valve effect multi-layered structure
 16 for providing longitudinal magnetic bias toward one direction to the
 free layer 10 of the multi-layered structure 16. Stacked structures of
 anti-ferromagnetic material layers and ferromagnetic material layers may
 be used for providing the longitudinal magnetic bias in stead of the
 permanent magnet layers 14 and 15.
 According to the invention, the constitution of the spin valve effect
 structure is not limited to a specific embodiment. Each layer of the
 structure can be made of any material with the necessary function. For
 example, the anti-ferromagnetic material layer 13 can be made of PtMn,
 NiMn or IrMn, the second ferromagnetic material layer 12 can be made of
 Co, FeCo or NiFe, the non-magnetic metallic material layer 11 can be made
 of Cu, Ag or Au, and the first ferromagnetic material layer 10 can be made
 of FeCo, NiCo or FeCoNi. The hard magnet layers 14 and 15 can be made of
 CoPt, CoCrPt or SmCo. The spin valve effect structure 16 can additionally
 include a seed or under layer, an electron reflection layer, a bias
 cancellation layer and/or a protection layer. Furthermore, the stacking
 order of each layer of the structure can be inverted as from the substrate
 the anti-ferromagnetic material layer, the second ferromagnetic material
 layer, the non-magnetic metallic material layer and the first
 ferromagnetic material layer.
 In the aforementioned specific embodiment, AITiC is used for the substrate,
 a two-layered structure of NiFe/Co is used for the first ferromagnetic
 material layer (free layer) 10, Cu is used for the non-magnetic metallic
 material layer 11, Co is used for the second ferromagnetic material layer
 (pinned layer) 12, and FeMn is used for the anti-ferromagnetic material
 layer 13. To fabricate the spin valve effect structure 16, an under seed
 layer of Al.sub.2 O.sub.3, an under shield layer of FeAISi and an under
 gap layer of Al.sub.2 O.sub.3 are deposited on an AlTiC substrate (wafer),
 and thereafter, a seed layer of Ta with 5 nm thickness, ferromagnetic
 material layers of NiFe with 9 nm thickness and Co with nm thickness which
 constitute the free layer 10, a non-magnetic metallic material layer 11 of
 Cu with 2.5 nm thickness, a ferromagnetic material layer of Co with 2.5 nm
 of thickness which constitutes the pinned layer 12, an anti-ferromagnetic
 material layer 13 of FeMn with 10 nm thickness and a protection layer of
 Ta with 5 nm thickness are sequentially deposited by Rf sputtering.
 After a patterned resist layer is formed, ion milling patterns the spin
 valve effect structure 16. Then, a seed layer of TiW with 10 nm thickness,
 magnet layers 14 and 15 of CoPt with 50 nm thickness and lead conductor
 layers of Ta with 50 nm thickness are stacked. Thereafter, an upper gap
 layer of Al.sub.2 O.sub.3 and an upper shield layer of NiFe are stacked.
 Thus, on the wafer, many spin valve effect MR sensors are formed. The
 above-mentioned processes for fabricating the MR sensors are known
 processes.
 According to the present invention, the following specific annealing
 processes for thus fabricated wafer to magnetize the free layer 10 and the
 pinned layer 12 of each MR sensor in directions orthogonal to each other
 are executed.
 First, an annealing process of the free layer 10 is executed. In this
 annealing process, as shown in FIG. 2a, the wafer is heated at about
 250.degree. C. under application of an external magnetic field of 1-3 kOe
 in a longitudinal direction (track-width direction) of each spin valve
 effect Mr sensor which is hereinafter referred to as a direction of
 longitudinal magnetic bias or a reference direction so that the axis of
 easy magnetization of the free layer 10 in each Mr sensor is directed
 toward the reference direction.
 Then, an annealing process for providing the exchange coupling magnetic
 bias to each spin valve effect Mr sensor is executed. In this annealing
 process, the temperature of the wafer is decreased to about 160.degree. C.
 and then the wafer is rotated by an angle which is greater than 90.degree.
 but equal to or less than 130.degree. under the application of the
 above-mentioned external magnetic field. Thus, the applied external
 magnetic field forms an angle that is more than 90.degree. but equal to or
 less than 130.degree. from the reference direction. The temperature of the
 wafer is then decreased to room temperature. According to this process, as
 shown in FIG. 2b, the exchange coupling magnetic bias Hex forms an angle
 which is more than 90.degree. but equal to or less than 130.degree. from
 the reference direction.
 Then, a magnet magnetization process is executed. In this process, a shown
 in FIG. 2c, the hard magnet layers 14 and 15 are magnetized toward the
 reference direction at normal room temperature so that the magnet layers
 14 and 15 produce the longitudinal magnetic bias Hhm (FIG. 1) in the
 reference direction.
 As aforementioned, the latter annealing process provides the exchange
 coupling magnetic bias with the Hex angle of more than 90.degree. over the
 whole region of the pinned layer 12 of each MR sensor. Thus, after the
 magnet magnetization process is executed, although angles .theta.p between
 the directions of the finally composed magnetization and the reference
 direction become less than 90.degree. at the both end portions of the
 pinned layer 12 of each MR sensor as shown in FIG. 2c, the total angles
 .theta.p become substantially 90.degree.(.theta.p.apprxeq.90.degree.) over
 the whole area of the pinned layer 12 as shown in FIG. 1.
 FIGS. 3 and 4 illustrate measured results of output voltage characteristics
 versus applied external magnetic field of a spin valve effect MR sensor
 with different Hex angles of 50.degree. to 130.degree.. The different Hex
 angles were provided to the sensor by changing the direction of the
 applied external magnetic field during the annealing process at angles of
 50.degree. to 130.degree. from the reference direction. The measurements
 were done for the spin valve effect MR sensor at normal room temperature
 using a .rho.-H tester. During the measurement, a sense current of 4 mA
 flowing toward the against direction which would result good symmetry in
 wave shape was applied to the sensor.
 FIG. 5 illustrates peak output voltage characteristics versus Hex angle of
 the spin valve effect MR sensor, obtained by calculating the
 aforementioned measured results of output voltage characteristics with
 respect to the applied external magnetic field. Also, FIG. 6 illustrates
 output asymmetry characteristics versus Hex angle of the spin valve effect
 MR sensor. As will be apparent from these figures, an output voltage of
 900 .mu.V or more can be obtained from the spin valve effect MR sensor and
 asymmetry of the output voltage can be kept within a permissible range
 when the Hex angle is more than 90.degree. but equal to or less than
 130.degree..
 FIG. 7 illustrates temperature dependency of the exchange coupling magnetic
 bias Hex of the spin valve effect MR sensor of this embodiment. The higher
 the temperature of the sensor, the lower the exchange coupling magnetic
 bias Hex. At about 160.degree. C., Hex=0.
 FIGS. 8 and 9 illustrate peak output voltage characteristics versus
 temperature of the spin valve effect MR sensor with different Hex angles
 under uniform magnetic field of 60 Oe.
 As shown in FIG. 8, when the Hex angle is between 50.degree. and
 90.degree., the larger Hex angle, the higher peak output voltage is
 provided. Within this range of the Hex angle, the peak output voltage is
 not kept high when the temperature increases. Also, as shown in FIG. 9,
 when the Hex angle is between 90.degree. and 130.degree., substantially
 the same peak output voltage is provided at the normal room temperature of
 about 25.degree. C. for the different Hex angles. Within this range of the
 Hex angle, the peak output voltage is kept high as well as that at the
 normal room temperature even when the temperature is within 50.degree. C.
 to 120.degree. C. Thus, it will be understood that, when the Hex angle is
 between 90.degree. and 130.degree., a high peak output voltage can be
 expected and this high peak output voltage can be maintained even if the
 temperature of the MR sensor increases.
 FIGS. 10a to 10d illustrate procedure of an annealing process in
 manufacturing a thin-film magnetic head as another embodiment according to
 the present invention. In this embodiment, the constitution of the spin
 valve effect structure and the wafer fabricating processes except for
 annealing processes are the same as these in the embodiment shown in FIG.
 1. Therefore, the following explanation of this embodiment is executed
 about annealing processes for the fabricated wafer to magnetize the free
 layer 10 and the pinned layer 12 of each MR sensor in directions
 orthogonal to each other.
 A first magnet magnetization process is executed. In this process, as shown
 in FIG. 10a, the hard magnet layers 14 and 15 are magnetized toward in a
 direction opposite that of the reference direction at normal room
 temperature so that the magnet layers 14 and 15 produce the longitudinal
 magnetic bias in the opposite direction against the reference direction.
 Then, an annealing process of the free layer 10 is executed. In this
 annealing process, as shown in FIG. 10b, the wafer is heated at about
 250.degree. C. under application of external magnetic field of 1-3 kOe in
 the reference direction so that the axis of easy magnetization of the free
 layer 10 in each MR sensor is directed toward the reference direction.
 Then, an annealing process for providing the exchange coupling magnetic
 bias to each spin valve effect MR sensor is executed. In this annealing
 process, the temperature of the wafer is decreased to about 160.degree. C.
 and then the wafer is rotated by 90.degree. under the application of the
 above-mentioned external magnetic field. Thus, the applied external
 magnetic field forms 90.degree. from the reference direction. The
 temperature of the wafer is then decreased to a room temperature.
 According to this process, as shown in FIG. 10c, at the center portion of
 the pinned layer 12, since there is no influence of the longitudinal
 magnetic bias in the opposite direction against the reference direction,
 the exchange coupling magnetic bias Hex forms 90.degree. from the
 reference direction. Whereas, at the both end portions of the pinned layer
 12, because there exists influence of the longitudinal magnetic bias in
 the opposite direction against the reference direction, the exchange
 coupling magnetic bias Hex forms an angle of more than 90.degree. from the
 reference direction.
 In case that residual magnetization of the hard magneto layers of CoPt 14
 and 15 is 750 emu/cm.sup.3, if the thickness of these layers are 20-50 nm,
 the longitudinal magnetic bias in the opposite direction against the
 reference direction of 250-1000 Oe will be applied into areas of the
 pinned layer 12 lying up to about 0.15 .mu.m length from the track ends.
 Thus, if the exchange coupling magnetic bias of 1000-2000 Oe in the
 transverse direction is provided at the annealing process, the composed
 magnetization of the lateral exchange coupling magnetic bias and the
 longitudinal magnetic bias will become equal to or more than 1000 and
 equal to or less than 130.degree. with respect to the reference direction.
 Then, a second magnet magnetization process is executed. In this process,
 as shown in FIG. 10d, the hard magnet layers 14 and 15 are magnetized
 toward the reference direction at the normal room temperature so that the
 magnet layers 14 and 15 produce the longitudinal magnetic bias in the
 reference direction.
 As aforementioned, the exchange coupling bias annealing process provides
 the exchange coupling magnetic bias with the Hex angle of
 100.degree.-140.degree. at the both end portions of the pinned layer 12 of
 each MR sensor. Thus, after the second magnet magnetization process is
 executed, angles .theta.p between the directions of the finally composed
 magnetization and the reference direction become substantially
 90.degree.(.theta.p .apprxeq.90.degree.) over the whole area of the pinned
 layer 12.
 Many widely different embodiments of the present invention may be
 constructed without departing from the spirit and scope of the present
 invention. It should be understood that the present invention is not
 limited to the specific embodiments described in the specification, except
 as defined in the appended claims.