Magnetic head and magnetic recording and reproducing apparatus

Abstract

The present application provides a magnetic head and a magnetic recording and reproducing apparatus in which the deterioration of a spin torque control element can be easily known. The magnetic head according to an embodiment includes a main pole, an auxiliary pole disposed apart from the main pole by a write gap, a spin torque control element disposed in the write gap, a bias current control section that supplies a bias current to the spin torque control element, and a resistance measurement section that measures a resistance value of the spin torque control element, wherein the difference between a first resistance value when the bias current is supplied with a polarity opposite to the polarity of the magnetization reversal of the spin torque control element and a second resistance value when the bias current is supplied with the polarity of the magnetization reversal of the spin torque control element is 4% or less.

Description

[0001] This application enjoys priority based on Japanese Patent Application No. 2022-014220 (filed on February 1, 2022). This application incorporates the entire contents of that basic application by reference. Technical Field

[0002] Embodiments of the present invention relate to magnetic heads and magnetic recording and reproducing apparatuses. Background Technology

[0003] In magnetic recording and playback devices equipped with auxiliary components such as spin torque control elements, signs of oxidation and degradation of the spin torque control element due to prolonged operation at high temperatures can be detected by an increase in the resistance of the spin torque control element. However, after a write operation, the spin torque control element is prone to becoming a disordered residual magnetized state. Consequently, the resistance value deviates due to the magnetoresistive effect, making it difficult to accurately detect the presence or absence of oxidation and degradation. Summary of the Invention

[0004] The present invention provides a magnetic head and a magnetic recording and reproducing apparatus in which the degradation of the spin torque control element can be easily detected.

[0005] According to the embodiment, it includes: a main magnetic pole; an auxiliary magnetic pole disposed with an open write gap from the main magnetic pole; a spin torque control element disposed in the write gap; a bias current control unit that supplies a bias current to the spin torque control element; and a resistance measuring unit that measures the resistance value of the spin torque control element, wherein the absolute difference between a first resistance value when the bias current is applied with the polarity of the magnetization reversal of the spin torque control element and a second resistance value when the bias current is applied with the polarity opposite to the magnetization reversal of the spin torque control element is 4% or less. Attached Figure Description

[0006] Figure 1 This is a block diagram that schematically illustrates a disk drive (HDD) according to an embodiment.

[0007] Figure 2 This is a side view showing the magnetic head, suspension, and recording medium in an HDD according to the implementation method.

[0008] Figure 3 It is a simplified cross-sectional view showing the head of the magnetic head and a portion of the disk used in the embodiment, magnified.

[0009] Figure 4 It is a simplified cross-sectional view showing the front end of the recording head and a portion of the disk used in the embodiment, magnified.

[0010] Figure 5 It means to make Figure 4 A cross-sectional view of the magnetic head after it has been in operation for an extended period of time.

[0011] Figure 6 This is a model diagram representing an example of the magnetization direction returning to the magnetic pole.

[0012] Figure 7 This is a model diagram representing an example of the magnetization direction of the magnetization control layer.

[0013] Figure 8 This is a diagram showing an example of the magnetization direction at the front end of the main magnetic pole.

[0014] Figure 9 It is a graph representing the results of the resistance measurement test of the sample.

[0015] Figure 10 It means Figure 9 A graph showing the proportion of the deviation in resistance values.

[0016] Figure 11 It is a graph showing the results of the resistance value measurement test of the sample involved in the implementation method.

[0017] Figure 12 It means Figure 11 A graph showing the proportion of the deviation in resistance values.

[0018] Figure 13 This is a schematic diagram illustrating the state of current flow biased by a bias current with reversed magnetization polarity.

[0019] Figure 14 This is a schematic diagram illustrating the state of a bias current being applied with a polarity opposite to that of the magnetization reversal.

[0020] Figure 15 This is a cross-sectional view that schematically illustrates other examples of magnetic heads used in the implementation.

[0021] Figure 16 This is a cross-sectional view that schematically illustrates other examples of magnetic heads used in the implementation.

[0022] Figure 17 This is a model diagram representing an example of the magnetization direction returning to the magnetic pole.

[0023] Figure 18 This is a model diagram representing an example of the magnetization direction of the magnetization control layer.

[0024] Figure 19 This is a diagram showing an example of the magnetization direction at the front end of the main magnetic pole.

[0025] Figure 20This is a flowchart illustrating an example of the detection process of the magnetoresistive effect.

[0026] Label Explanation

[0027] 11. Frame, 12. Disk, 13. ABS, 14. Spindle Motor, 15. Slider, 16. Magnetic Head, 17. Head, 18. Head Actuator, 30. Head Amplifier IC, 40. Main Controller, 54. Replay Head, 58. Recording Head, 60. Main Magnetic Pole, 62. Auxiliary Magnetic Pole, 64. Lead Core, 65. Spin Torque Control Element, 65-1. Stack, 65a. First Non-Magnetic Conductive Layer, 65b. Second Non-Magnetic Conductive Layer, 65c. Magnetization Control Layer, 81. Recording Current Supply Circuit, 82. Auxiliary Element Current Supply Circuit, 83. Heater Voltage Supply Circuit, 84. Read Voltage Supply Circuit, 85. Auxiliary Element Resistance Measurement Circuit Detailed Implementation

[0028] The magnetic head according to the embodiment includes: a main magnetic pole; an auxiliary magnetic pole disposed with an open write gap from the main magnetic pole; a spin torque control element disposed in the write gap; a bias current control unit that supplies bias current to the spin torque control element; and a resistance measuring unit that measures the resistance value of the spin torque control element. In the magnetic head according to the embodiment, the absolute value of the difference between a first resistance value when the bias current is applied with the polarity of the magnetization reversal of the spin torque control element and a second resistance value when the bias current is applied with the polarity opposite to the first resistance value is 4% or less.

[0029] Other embodiments of the magnetic head include: a main magnetic pole; an auxiliary magnetic pole disposed with an open write gap from the main magnetic pole; and a spin torque control element disposed in the write gap. In the magnetic head of the second embodiment, the absolute value of the magnetoresistive effect between the spin torque control element and the auxiliary magnetic pole or between the spin torque control element and the main magnetic pole is 4% or less.

[0030] In addition, another embodiment of the magnetic recording and reproduction apparatus includes the magnetic head of the embodiment or the magnetic head of other embodiments.

[0031] According to the embodiment, the magnetic head can suppress the resistance value deviation of the spin torque control element after the write operation by having an absolute value of 4% or less of the difference between the first resistance value and the second resistance value, or by having an absolute value of 4% or less of the magnetoresistive effect between the spin torque control element and the auxiliary magnetic pole or between the spin torque control element and the main magnetic pole, and can detect signs of oxidation and deterioration of the spin torque control element with good accuracy from the resistance change.

[0032] The spin torque control element may include a magnetization control layer and a non-magnetic conductive layer.

[0033] The spin torque control element can use multiple magnetized control layers and non-magnetic conductive layers, and can alternately stack magnetized control layers and non-magnetic conductive layers.

[0034] In order to make the absolute value of the difference between the first resistance value and the second resistance value less than 4%, or to make the absolute value of the magnetoresistive effect between the spin torque control element and the auxiliary magnetic pole or between the spin torque control element and the main magnetic pole less than 4%, the material or thickness of the magnetization control layer or the non-magnetic conductive layer can be adjusted.

[0035] The magnetization control layer can be an alloy containing at least one first element selected from iron (Fe), cobalt (Co), and nickel (Ni). Furthermore, the magnetization control layer can be composed of an alloy material containing both a first element and a second element, wherein the second element is at least one selected from chromium (Cr), vanadium (V), manganese (Mn), titanium (Ti), scandium (Sc), molybdenum (Mo), palladium (Pd), and iridium (Ir).

[0036] Alternatively, the magnetization control layer may be composed of a stack of at least one first element selected from Fe, Co, and Ni, and a second element other than the first element. Further, the second element may be at least one selected from Cr, V, Mn, Ti, Sc, Mo, Pd, and Ir.

[0037] For example, the absolute value of the spin polarization of the magnetization control layer can be set to 0 to 0.2. Examples of materials with such properties include FeCr and FeV.

[0038] When the thickness of the magnetization control layer is set to tF and the spin diffusion length is set to λF, it can be assumed that tF ≤ λF. Assuming that the spin torque control element operates due to the spin torque between itself and the auxiliary magnetic pole, the spin diffusion length λF is the distance by which the spin of conduction electrons, which is unbiased in the direction injected from the non-magnetic conductive layer on the main magnetic pole side to the magnetization control layer, changes direction as it is mitigated by conduction from the magnetization control layer to the non-magnetic conductive layer side on the auxiliary magnetic pole side. Therefore, when tF ≤ λF and the spin diffusion length λF of the magnetization control layer is long, even if the spin polarization of the magnetization control layer is high, the spin information from the injected non-magnetic conductive layer is not lost, and no bias occurs in the direction of the spin flowing from the magnetization control layer to the auxiliary magnetic pole side. Therefore, it tends not to produce a change in resistance when the magnetization direction of the magnetization control layer and the auxiliary magnetic pole changes.

[0039] Furthermore, when the thickness of the non-magnetic conductive layer on the interface side generating the spin torque is set as ts, and the spin diffusion length is set as λs, it can be assumed that ts ≥ λs. Assuming that the spin torque control element operates due to the spin torque between itself and the auxiliary magnetic pole, the spin diffusion length λs is a distance such that the spin of conduction electrons biased in the direction flowing from the magnetization control layer to the auxiliary magnetic pole is moderated, and their direction changes to a distance without bias in that direction. Therefore, when ts ≥ λs, even if the spin polarization of the magnetization control layer is large, no bias is generated in the direction of the spin flowing from the magnetization control layer to the auxiliary magnetic pole. Thus, there is a tendency not to produce a change in resistance when the magnetization direction of the magnetization of the magnetization control layer and the auxiliary magnetic pole changes.

[0040] Furthermore, the thickness of the magnetization control layer can be set to 0.5 nm or more and 20 nm or less. When the film thickness is as thin as less than 0.5 nm, there is a tendency for the magnetization to disappear due to insufficient crystal growth. On the other hand, in order to ensure the recording performance of the recording lines of the recording head, the write gap length is preferably generally 20 nm or less, so the thickness of the magnetization control layer can be set to 20 nm or less even at its maximum.

[0041] When the non-magnetic conductive layer on the main magnetic pole side is designated as the first non-magnetic conductive layer and the non-magnetic conductive layer on the auxiliary magnetic pole side is designated as the second non-magnetic conductive layer, materials with short spin diffusion lengths, such as Ta, Ru, and Ir, can be used as the first non-magnetic conductive layer, while materials with long spin diffusion lengths, such as Cu, Ag, Cr, and NiCr, can be used as the second non-magnetic conductive layer. Furthermore, the first and second non-magnetic conductive layers can be interchanged.

[0042] The embodiments will now be described with reference to the accompanying drawings.

[0043] Furthermore, the disclosed example is merely one instance, and any technical solutions that can be readily conceived by those skilled in the art while maintaining the spirit of the invention are naturally included within the scope of this invention. Additionally, to make the description clearer, the drawings sometimes schematically represent the width, thickness, shape, etc., of various parts compared to the actual form; however, this is merely an example and does not limit the interpretation of the invention. Furthermore, in this specification and the drawings, sometimes the same reference numerals are given to elements that have been described in the preceding drawings, and detailed descriptions are appropriately omitted.

[0044] Example 1

[0045] Figure 1 This is a block diagram that schematically represents a hard disk drive (HDD) as an embodiment of the disk device. Figure 2 This is a side view showing the read / write head and disk in a suspended state. Figure 3 It is a cross-sectional view that roughly represents the head of the read / write head and a portion of the disk.

[0046] like Figure 1 As shown, the HDD 10 includes a rectangular frame 11, a disk 12 serving as the recording medium disposed within the frame 11, a spindle motor 14 supporting and rotating the disk 12, and multiple read / write heads 16 for writing and reading data from the disk 12. Additionally, the HDD 10 includes a head actuator 18 that moves and positions the read / write heads 16 onto any track on the disk 12. The head actuator 18 includes a suspension assembly 20 that supports the read / write heads 16 in a manner that enables their movement, and a voice coil motor (VCM) 22 that rotates the suspension assembly 20.

[0047] HDD10 includes a head amplifier IC30, a main controller IC40, and a driver IC48. The head amplifier IC30 is disposed, for example, in the suspension assembly 20 and electrically connected to the read / write head 16. The main controller IC40 and the driver IC48 are configured, for example, on a control circuit board (not shown) disposed on the rear side of the housing 11. The main controller 40 includes an R / W channel (RDC) 42, a hard disk controller (HDC) 44, and a microprocessor (MPU) 46. The main controller 40 is electrically connected to the head amplifier IC30 and, via the driver IC48, to the VCM 22 and the spindle motor 14. HDD10 can be connected to a host computer (not shown).

[0048] like Figure 1 and Figure 2 As shown, the disk 12 is a vertical magnetic recording medium with a recording layer that is anisotropic in a direction perpendicular to the disk surface. Specifically, the disk 12 has, for example, a substrate 101 formed of a non-magnetic material in the shape of a circular plate with a diameter of approximately 2.5 inches (6.35 cm). A soft magnetic layer 102 as a base layer, a magnetic recording layer 103 on top of it, and a protective film 104 are sequentially stacked on each surface of the substrate 101. The disk 12 is coaxially fitted into the hub of a spindle motor 14. The disk 12 rotates at a predetermined speed in the direction of arrow B via the spindle motor 14.

[0049] The suspension assembly 20 has a bearing portion 24 that is rotatably fixed to the frame 11, and a plurality of suspension elements 26 extending from the bearing portion 24. For example... Figure 2 As shown, the magnetic head 16 is supported on the extended ends of each suspension 26. The magnetic head 16 is electrically connected to the head amplifier IC 30 via a wiring component 28 provided on the suspension assembly 20.

[0050] Next, the structure of the magnetic head 16 will be explained in detail.

[0051] like Figure 2 and Figure 3 As shown, the magnetic head 16 is configured as a levitation head, having a slider 15 formed in a generally rectangular parallelepiped shape and a head 17 formed at the end of the slider 15 on the outflow end (tail) side. The slider 15 is formed, for example, from a sintered body of alumina and titanium carbide (AlTiC), and the head 17 is formed from a multilayer thin film.

[0052] The slider 15 has a rectangular ABS (air support surface) 13 facing the surface of the disk 12. The slider 15 is maintained in a state where it is suspended a predetermined amount from the surface of the disk 12 by the airflow C generated between the disk surface and the ABS 13 due to the rotation of the disk 12. The direction of the airflow C is consistent with the rotation direction B of the disk 12. The slider 15 has a leading end 15a located on the inflow side of the airflow C and a trailing end 15b located on the outflow side of the airflow C.

[0053] like Figure 3 As shown, the head 17 is a separate magnetic head, consisting of a playback head 54 and a recording head 58, formed on the trailing end 15b of the slider 15 using a thin-film process. To control the recording and playback suspension of the head 17, a recording heater 19a is disposed on the depth side of the recording head 58, and a playback heater 19b is disposed on the depth side of the playback head 54. The playback head 54 consists of a playback element 55 based on a magnetic film exhibiting a magnetoresistive effect, and an upper shield 56 and a lower shield 57, on the trailing and leading sides of the playback element 55 respectively, sandwiching the magnetic film-based playback element 55. The lower ends of these playback elements 55, the upper shield 56, and the lower shield 57 are exposed at the ABS 13 of the slider 15. The playback head 54 is connected to the head amplifier IC 30 via electrodes (not shown), wiring, and wiring components 28, and outputs the read data to the head amplifier IC 30.

[0054] The recording head 58 is positioned relative to the playback head 54 on the tail end 15b side of the slider 15. The recording head 58 includes: a main magnetic pole 60 formed of a high-permeability material that generates a recording magnetic field perpendicular to the surface of the disk 12; a return magnetic pole 62 that serves as a tail shield (write shield, first shield); and a leader core 64 that serves as a leader shield (second shield). The main magnetic pole 60 and the return magnetic pole 62 constitute a first magnetic core forming a magnetic circuit, and the main magnetic pole 60 and the leader core 64 constitute a second magnetic core forming a magnetic circuit. The recording head 58 has a first coil (recording coil) 70 wound around the first magnetic core and a second coil (recording coil) 72 wound around the second magnetic core.

[0055] like Figure 3As shown, the main magnetic pole 60 extends approximately perpendicularly to the surface of the disk 12. The front end 60a of the main magnetic pole 60 on the disk 12 side narrows towards the disk surface in a tapering manner, for example, with a trapezoidal cross-section. The front end face of the main magnetic pole 60 is exposed at the ABS13 of the slider 15. The width of the trailing end face 60b of the front end 60a approximately corresponds to the width of the track in the disk 12.

[0056] A return magnetic pole 62, formed of a soft magnetic material, is disposed on the trailing side of the main magnetic pole 60, and is configured to efficiently close the magnetic circuit via the soft magnetic layer 102 of the disk 12 directly below the main magnetic pole 60. The return magnetic pole 62 is formed in a generally L-shape and has a first connection portion 50 connected to the main magnetic pole 60. The first connection portion 50 is connected to the upper part of the main magnetic pole 60, i.e., the part of the main magnetic pole 60 that is separated from the ABS 13, via a non-conductive material 52.

[0057] The front end 62a of the return magnetic pole 62 is formed into an elongated rectangular shape, with its front end face exposed at the ABS13 of the slider 15. The leading side end face 62b of the front end 62a extends along the width direction of the track of the disk 12, and extends approximately perpendicularly to the ABS13. This leading side end face 62b faces approximately parallel to the tail side end face 60b of the main magnetic pole 60, which is open to the write gap WG.

[0058] The first coil 70 is configured to be wound in a magnetic circuit (first magnetic core) including the main magnetic pole 60 and the return magnetic pole 62. The first coil 70 is wound, for example, around the first connection portion 50. By circulating a recording current in the first coil 70 when a signal is written to the disk 12, the first coil 70 excites the main magnetic pole 60 to circulate magnetic flux in the main magnetic pole 60.

[0059] The spin torque control element 65 is disposed within the write gap WG between the front end 60a of the main magnetic pole 60 and the return magnetic pole 62, with a portion of it exposed in the ABS13. The lower end face of the spin torque control element 65 is not limited to being located coplanar with the ABS13, but may also be located upwards in the height direction from the ABS13. Furthermore, the spin torque control element is an example of an auxiliary element, for example, it could be a structure intended to provide an auxiliary effect associated with flux control, which is achieved by using the spin torque to reverse the magnetization in the opposite direction to the flux direction within the write gap; or it could be a structure intended to provide a high-frequency auxiliary effect (high-frequency auxiliary element), which induces resonance in the magnetization of the medium by using the spin torque to oscillate the magnetization at a high frequency.

[0060] like Figure 3As shown, connection terminals 91 and 92 are connected to the main magnetic pole 60 and the return magnetic pole 62, respectively. These connection terminals 91 and 92 are connected to the head amplifier IC 30 via wiring. Thus, the current circuit is configured to allow current to flow from the head amplifier IC 30 through the main magnetic pole 60, the spin torque control element 65, and the return magnetic pole 62 in series. Additionally, connection terminals 97 and 98 are connected to the recording heater 19a and the playback heater 19b, respectively. These connection terminals 97 and 98 are connected to the head amplifier IC 30 via wiring.

[0061] like Figure 3 As shown, a leader core 64 formed of a soft magnetic material is disposed opposite to the main magnetic pole 60 on the leader side of the main magnetic pole 60. The leader core 64 is formed in a generally L-shape, and the front end portion 64a on the disk 12 side is formed in an elongated rectangular shape. The front end face (lower end face) of this front end portion 64a is exposed in the ABS13 of the slider 15. The trailing end face 64b of the front end portion 64a extends along the width direction of the magnetic track of the disk 12. This trailing end face 64b faces the leader end face of the main magnetic pole 60 with an open gap. This gap is covered by a protective insulating film 76, which is a non-magnetic material.

[0062] The leader core 64 has a second connection portion 68 at its exit from the disk 12, which engages in the back gap between the leader core 64 and the main magnetic pole 60. This second connection portion 68 is formed, for example, of a soft magnetic material, and together with the main magnetic pole 60 and the leader core 64, forms a magnetic circuit. The second coil 72 of the recording head 58 is configured to be wound around the magnetic circuit (second core) including the main magnetic pole 60 and the leader core 64, applying a magnetic field to the magnetic circuit. The second coil 72 is wound, for example, around the second connection portion 68. Alternatively, a non-conductive or non-magnetic material may be inserted into a portion of the second connection portion 68.

[0063] The second coil 72 is wound in the opposite direction to the first coil 70. The first coil 70 and the second coil 72 are connected to terminals 95 and 96, respectively, which are connected to the head amplifier IC 30 via wiring. The second coil 72 can also be connected in series with the first coil 70. Alternatively, the first coil 70 and the second coil 72 can be configured to control their current supply independently. The current supplied to the first coil 70 and the second coil 72 is controlled by the head amplifier IC 30 and the main controller 40.

[0064] like Figure 1As shown, the head amplifier IC 30 that drives the magnetic head 16 and the recording head 58 includes: a recording current supply circuit 81 that supplies recording current to the first coil 70 and the second coil 72 via connection terminals 95 and 96; an auxiliary element current supply circuit 82 serving as a bias current control unit that supplies bias current to the spin torque control element 65 via wiring and connection terminals 91 and 92 (not shown); a heater voltage supply circuit 83 that supplies heater voltage to the recording heater 19a and the playback heater 19b via wiring and connection terminals 97 and 98 (not shown); a read voltage supply circuit 84 that reads the playback signal recorded on the disk 12 after applying voltage to the playback element section of the magnetic head; and a resistance measurement circuit 85 serving as an auxiliary element resistance measurement unit that measures the resistance value of the spin torque control element 65. Furthermore, although not shown, it includes: a timing calculation unit (not shown) that controls the timing and duration of current flow in the recording current supply circuit 81, and controls the timing and duration of voltage application to the spin torque control element voltage supply circuit 82; and a recording current waveform generator (not shown) that generates a recording current waveform based on the recording mode signal generated in the R / W channel 42. The auxiliary element resistance measurement circuit 85 monitors the deterioration of the spin torque control element 65 by periodically measuring and detecting the resistance value.

[0065] Figure 4 It is a simplified cross-sectional view showing the front end of the recording head and a portion of the disk used in the embodiment, magnified.

[0066] Figure 5 It means to make Figure 4 A cross-sectional view of the magnetic head after it has been in operation for an extended period of time.

[0067] like Figure 4As shown, the spin torque control element 65 has: a first non-magnetic conductive layer 65a disposed on the main magnetic pole 60a, formed of a material with a short spin diffusion length; a magnetization control layer 65c disposed on the first non-magnetic conductive layer 65a; and a second non-magnetic conductive layer 65b disposed on the magnetization control layer 65c, formed of a material with a long spin diffusion length. As described above, by applying a bias current of a certain value or higher through the ab-head amplifier IC30 via the main magnetic pole 60, the spin torque control element 65, and the return magnetic pole 62 in series, according to the polarity of electrons flowing from the magnetization control layer 65c to the return magnetic pole 62a, the magnetization control layer 65c can be oscillated by the spin torque reflected from the return magnetic pole 62a. Here, the first non-magnetic conductive layer 65a can be omitted as needed. Alternatively, on the main magnetic pole 60a, the bias current can be applied in the opposite order to the formation of the magnetization control layer 65c, the magnetization control layer 65c and the second non-magnetic conductive layer 65b, in the polarity from the main magnetic pole 60a through the second non-magnetic conductive layer 65b, the magnetization control layer 65c and the magnetization control layer 65c to the return magnetic pole 62a.

[0068] To drive the spin torque control element 65, current needs to be applied. This causes the spin torque control element 65 to heat up; therefore, when it operates for extended periods, especially in high-temperature environments, [the following occurs]. Figure 5 As shown, the self-rotation torque control element 65 will form an oxide layer 200 that is deteriorated due to oxidation from the ABS surface side, which will cause problems in reliability.

[0069] Power-on test

[0070] For the purpose of electrical testing, a film of the spin torque control element 65 was formed by sequentially stacking layers of the following materials and thicknesses between the main magnetic pole 60 and the return magnetic pole 62 formed of FeCo, starting from the main magnetic pole 60, and samples 1 to 10 were made.

[0071] Samples 1-10

[0072] First non-magnetic conductive layer 65a Ta 10nm

[0073] Magnetization control layer 65c NiFe 5nm

[0074] Second non-magnetic conductive layer 65b Cu 2nm

[0075] For samples 1-10, a continuous 7mA current was applied to the spin torque control element for an extended period without any write operation at a high temperature of 100°C. An example of the results is shown in Table 1 below.

[0076] Table 1

[0077]

[0078]

[0079] As shown in samples 2 and 10 in Table 1, signs of oxidation and deterioration of the spin torque control element 65 can be observed when the resistance change rate of the spin torque control element 65 is approximately +4% or more. During the drive operation, the deterioration of the spin torque control element 65 can also be monitored by periodically detecting the resistance value in the auxiliary element resistance measurement circuit 85 within the head amplifier IC30.

[0080] Figure 6 It means from Figure 4 The direction of arrow 201 is observed as an example of the magnetization direction of the returning magnetic pole, as shown in the model diagram.

[0081] Figure 7 It means from Figure 4 The direction of arrow 201 is observed in a model diagram of an example of the magnetization direction of the magnetization control layer.

[0082] Figure 8 It means from Figure 4 The diagram shows an example of the magnetization direction observed at the front end of the main magnetic pole, as indicated by arrow 201.

[0083] In the diagram, 203, 204, and 205 are arrows indicating the magnetization direction. 13 represents the ABS side.

[0084] like Figures 6-8 As shown, even after a demagnetization operation based on demagnetization is performed, the magnetization of the return magnetic pole 62a, the magnetization control layer 65c, and the front end of the main magnetic pole 60 remains in the plane of the fabricated film in a state of disordered orientation. Therefore, a magnetoresistive effect is generated corresponding to the relative angle between the in-plane magnetization of the magnetization control layer 65c and the in-plane magnetization of the return magnetic pole 62a, and the resistance value will change due to the magnetization state after writing.

[0085] Resistance value measurement test

[0086] Sample 11 was made in the same manner as the sample used in the above-mentioned power-on test, and the resistance value of the spin torque control element 65 after the writing action was repeatedly observed, and a resistance value measurement test was carried out.

[0087] exist Figure 9 The graph shown represents the results of the resistance measurement test of the sample.

[0088] exist Figure 10 The text shows the representation. Figure 9 A graph showing the proportion of the deviation in resistance values.

[0089] like Figure 9 As shown, in the sample, a deviation in resistance value occurs accompanied by the magnetoresistance effect, such as... Figure 10 As shown, the rate of change relative to the measured minimum value shows a resistance change rate close to 4% when the spin torque control element has undergone oxidative degradation. Therefore, it is difficult to detect whether the spin torque control element has deteriorated based solely on the resistance value. Thus, a structure that intentionally suppresses the magnetoresistive effect is preferred to suppress resistance deviation.

[0090] As with the sample used in the energized test, the magnetoresistive effect in the structure of a vertically energized giant magnetoresistive element (CPP-GMR element) consisting of a main magnetic pole 60a, a spin torque control element 65, and a return magnetic pole 62a, can be represented by the Valet-Fert model. In the case of a simple symmetry system, when the spin polarization of the ferromagnetic material is set to β, the resistivity is set to ρF, and the film thickness is set to tF, the rate of change of area resistivity ΔRA (%) accompanying the magnetoresistive effect can be represented by the following equation (1).

[0091]

[0092] The conductivity of ferromagnetic materials typically formed from Fe, Co, or Ni does not vary significantly depending on the material. Furthermore, assuming the same film thickness in the design, the ΔRA (resistivity change rate based on the magnetoresistance effect) is influenced by the spin polarization β of the ferromagnetic material. As exemplified by the spin torque control element used in the energized test sample, where a spin torque control element made of a typical Fe, Co, or Ni-based alloy is used as the magnetization control layer 65c between the main magnetic pole 60a and the return magnetic pole 62a, β is as large as 0.4–0.5, exhibiting... Figure 9 As shown in the diagram, there is a large magnetoresistance effect. Given this situation, in order to suppress resistance deviation, it is preferable to use a material with a small absolute value of β.

[0093] As for the sample 12 involved in the embodiment, a film of a spin torque control element 65 was formed by sequentially stacking layers of the following materials and thicknesses from the main magnetic pole 60 and the return magnetic pole 62 formed of FeCo between the main magnetic pole 60 and the return magnetic pole 62.

[0094] Sample 12

[0095] First non-magnetic conductive layer 65a Ta 10nm

[0096] Magnetization control layer 65c FeCr 5nm

[0097] Second non-magnetic conductive layer 65b Cu 2nm

[0098] Furthermore, it is known that FeCr has an absolute value of β below 0.1.

[0099] Regarding sample 12, the resistance value of the spin torque control element after the write operation was repeatedly observed, and the resistance value measurement test was carried out in the same way as the sample.

[0100] exist Figure 11 The graph shown represents the results of resistance measurement tests on the samples involved in the embodiments.

[0101] exist Figure 12 The text shows the representation. Figure 11 A graph showing the proportion of the deviation in resistance values.

[0102] like Figure 11 As shown in sample 12 of the embodiment, it can be seen that by forming a magnetization control layer using a material that suppresses the absolute value of spin polarization, the magnetoresistance effect can be reduced. As a result, as... Figure 12 As shown, this can significantly reduce resistance deviation.

[0103] Furthermore, FeCr is used in the magnetization control layer 65c as a material with an absolute value of approximately 0.1 for β. However, as a material for the magnetization control layer, an alloy material containing at least one first element from Fe, Co, and Ni and at least one second element from Cr, V, Mn, Ti, Sc, Mo, Pd, and Ir can be used.

[0104] Alternatively, artificial lattices of elements 1 and 2 can be used to replace alloy materials containing elements 1 and 2.

[0105] As an example of the embodiment, sample 13 can be used to form a film of the spin torque control element 65 by sequentially stacking layers of the following materials and thicknesses from the main magnetic pole 60 and the return magnetic pole 62 formed of FeCo between the main magnetic pole 60 and the return magnetic pole 62.

[0106] Sample 13

[0107] First non-magnetic conductive layer 65a Ta 10nm

[0108] As the magnetization control layer 65c, an artificial lattice of 5nm was obtained by repeatedly stacking 10 layers of the first element Fe (0.3nm) and the second element Cr (0.2nm).

[0109] Second non-magnetic conductive layer 65b Cu 2nm

[0110] Regarding sample 13, by stacking Fe / Cr, it is also possible to reduce the deviation of the resistance value of the spin torque control element after the write operation in the same way as sample 12, which uses FeCr with a small spin polarization β.

[0111] Furthermore, in the spin torque control element according to the embodiment, a substrate layer may be further provided between the main magnetic pole 60 and the first non-magnetic conductive layer 65a. Examples of substrate layers include Ta and Ru. The main magnetic pole 60 and the first non-magnetic conductive layer 65a may also be in contact.

[0112] A capping layer may be further provided between the second non-magnetic conductive layer 65b and the return magnetic pole 62. Examples of capping layers include Ta and Ru. The second non-magnetic conductive layer 65b and the return magnetic pole 62 may also be in contact.

[0113] Regarding the magnetoresistive effect, it can also be detected in a form that differs from the resistance deviation of the spin torque control element after writing.

[0114] exist Figure 13 The diagram shows a state where a bias current is applied with the polarity of magnetization reversed.

[0115] For example, when a spin torque control element with the same structure as samples 1 to 11 is fabricated, for example, a spin torque control element 65 consisting of a 10 nm Ta first non-magnetic conductive layer 65a, a 5 nm NiFe magnetization control layer 65c, and a 2 nm Cu second non-magnetic conductive layer 65b is fabricated between the main magnetic pole 60 formed of FeCo and the return magnetic pole 62, and a disk device is fabricated, a recording current supply circuit 81 is used. As shown in the figure, with a DC current of about 20 to 50 mA applied to the recording coil, a current of about 3 to 5 mA is applied to the spin torque control element with the polarity of electrons flowing from the magnetization control layer 65c to the return magnetic pole 62a, i.e., the polarity of magnetization reversal. As a result, the magnetization of the magnetization control layer 65c is reversed due to the spin torque reflected from the return magnetic pole 62a.

[0116] Here, the amount of current energized to the spin torque control element can also be adjusted according to the film thickness and saturation magnetization of the magnetization control layer 65c. At this time, the magnetization of the magnetization control layer 65c and the return magnetic pole 62a becomes antiparallel, so the resistance value of the spin torque control element will increase due to the magnetoresistance effect between the two layers.

[0117] exist Figure 14 The diagram shows a situation where a bias current is applied with a polarity opposite to that of the magnetization reversal.

[0118] On the other hand, such as Figure 14As shown, when the bias polarities are reversed under the same recording coil current and bias current, the magnetization of the magnetization control layer 65c becomes synchronized with the magnetization of the return magnetic pole 62a due to the transmission spin torque from the return magnetic pole 62a to the magnetization control layer 65c. In this case, the magnetization of the magnetization control layer 65c and the return magnetic pole 62a becomes parallel, therefore, the resistance of the spin torque control element decreases. By calculating these... Figure 13 , 14 The difference in resistance value of the spin torque control element can be used to detect the magnetoresistive effect of the spin torque control element.

[0119] For example, by periodically monitoring the resistance value of the spin torque control element during drive operation, the oxidation degradation of the spin torque control element can be detected.

[0120] exist Figure 20 The diagram shows a flowchart illustrating an example of the detection process for the magnetoresistive effect.

[0121] As shown in the figure, firstly, after a certain period of time in the normal recording and playback mode, it is determined whether there is a requirement for magnetoresistive effect measurement (S1). If there is no requirement, the system switches to the normal recording and playback mode (S10). If there is a requirement, after the corresponding magnetic head performs a track seek operation to the dedicated track (S2), a DC current of 20-50mA is applied to the recording coil (S3).

[0122] Next, the spin torque control element is energized with the desired current from the auxiliary element current supply circuit 82 in the positive direction (the direction in which electrons flow from the magnetization control layer to the return magnetic pole) (S4). Here, the current amount can be set to 3 to 5 mA when the magnetization control layer is formed of 5 nm NiFe with a saturation magnetization of 1 T. This current amount can be adjusted according to the film thickness and saturation magnetization. Next, the resistance value Rp of the spin torque control element is measured by applying a voltage back in the auxiliary element resistance measurement supply circuit 85 (S5). Similarly, the spin torque control element is energized with the same current amount as in (S4) from the auxiliary element current supply circuit 82 in the negative direction (the direction in which electrons flow from the return magnetic pole to the magnetization control layer) (S6). The resistance value Rn of the spin torque control element is measured in the auxiliary element resistance measurement supply circuit 85 (S7). Here, the magnetoresistive effect (S8) generated when the magnetization of the magnetization control layer and the magnetization of the return magnetic pole are parallel / antiparallel can be calculated by the following equation (2).

[0123] |Rp-Rn| / Rn …(2)

[0124] After calculating the magnetoresistive effect, the power supply to the spin torque control element from the auxiliary element current supply circuit 82 is disconnected (S9), and the system switches to the normal recording and playback mode (S10).

[0125] exist Figure 15 In the example shown, as an example of detecting the oxidation degradation of the spin torque control element by periodically monitoring the resistance value of the spin torque control element during drive operation, a graph showing the relationship between write time and the resistance value of the spin torque control element is presented.

[0126] In the figure, 220 represents the measurement result of the spin torque control element used in the embodiment, which is composed of 65a of Ta (10nm), 65c of FeCr (5nm), and 65b of Cu (2nm), and 221 represents the measurement result of a comparative spin torque control element composed of 65a of Ta (10nm), 65c of NiFe (5nm), and 65b of Cu (2nm).

[0127] As shown in 221, in the measurement results of the compared spin torque control element, the resistance deviation caused by the magnetoresistive effect of residual magnetization after writing increases, resulting in false detection of oxidation degradation. In contrast, as shown in 220, when 5nm FeCr with an absolute value of β as small as ~0.1 is used as the magnetization control layer 65c, the resistance deviation can be suppressed, and the degradation of the spin torque control element can be detected with good accuracy based on the resistance value.

[0128] Example 2

[0129] Regarding the magnetoresistance effect between the magnetization control layer 65c and the return magnetic pole 62a as described in Example 1, if we assume it to be a symmetric system, then as shown in Equation (1), it can also be reduced by thinning the film thickness tF of the ferromagnetic material, i.e., the magnetization control layer 65c. Furthermore, when the spin diffusion length of the magnetization control layer 65c is set to λF, by designing the film thickness to be such that tF≤λF, β can be effectively reduced without spin polarization. Therefore, by designing the film thickness of the magnetization control layer 65c to be such that tF≤λF, the magnetoresistance effect can also be largely eliminated. For example, when a NiFe film with a thickness tF of 5 nm and a spin diffusion length λF of approximately 3 nm is fabricated as the magnetization control layer 65c, tF ≥ λF. Therefore, sufficient spin polarization will occur at the interface of the second non-magnetic conductive layer, resulting in a magnetoresistance effect. However, by using FeCo or FeCr films with a thickness tF of 5 nm and a spin diffusion length λF of approximately 10 nm as alternative materials, the magnetoresistance effect can be largely eliminated.

[0130] Example 3

[0131] The magnetoresistance effect between the magnetization control layer 65c and the return magnetic pole 62a, as described in Example 1, can be reduced by selecting the material of the second non-magnetic conductive layer 65b between the two layers.

[0132] Specifically, when the thickness of the second non-magnetic conductive layer 65b is set to ts and the spin diffusion length is set to λs, the magnetoresistance effect can be largely eliminated by setting ts≥λs.

[0133] For example, in the case of a spin torque control element composed of a first non-magnetic conductive layer 65a of 10 nm Ta, a magnetization control layer 65c of 5 nm NiFe, and a second non-magnetic conductive layer 65b of 2 nm Cu with a spin diffusion length λs of 500 nm or less, ts << λs, thus tending to produce resistance deviations due to the magnetoresistance effect. On the other hand, by replacing the 2 nm Cu with a film of Ta or Ir with a spin diffusion length λs of 1 to 2 nm of 2 nm as the second non-magnetic conductive layer 65b, the magnetoresistance effect can be largely eliminated.

[0134] Example 4

[0135] An example of a stacked structure using multiple magnetization control layers and multiple non-magnetic conductive layers is shown as a spin torque control element.

[0136] Figure 16 The diagram shows a cross-sectional view that schematically represents other examples of magnetic heads used in the embodiments.

[0137] As shown in the figure, the spin torque control element 65, in addition to having a first non-magnetic conductive layer 65a formed of a material with a short spin diffusion length and disposed on the main magnetic pole 60a, and a stack 65-1, has the same... Figure 4 Similarly, the stack 65-1 consists of a magnetization control layer 65e alternately disposed on a conductive layer 65a, a second non-magnetic conductive layer 65d disposed on the magnetization control layer 65e and formed of a material with a long spin diffusion length, the magnetization control layer 65e, and the second non-magnetic conductive layer 65d. Here, the non-magnetic conductive layer 65a can be omitted as needed. Alternatively, on the main magnetic pole 60a, the bias current can be applied in the opposite order to the formation of the magnetization control layer 65e, the magnetization control layer 65e, and the second non-magnetic conductive layer 65d, so that the bias current flows from the main magnetic pole 60a through the second non-magnetic conductive layer 65d, the magnetization control layer 65e, the second non-magnetic conductive layer 65d, and the magnetization control layer 65e to the return magnetic pole 62a.

[0138] Between the main magnetic pole 60 and the return magnetic pole 62 formed of FeCo, layers of the following materials and thicknesses are sequentially stacked starting from the main magnetic pole 60 to form a film for the spin torque control element 65, thus producing sample 14.

[0139] Sample 14

[0140]

[0141] In such Figure 16 In the case where a non-magnetic conductive layer 65d and a magnetization control layer 65e are stacked on the return magnetic pole 62, the second non-magnetic conductive layer 65b can be omitted.

[0142] Figure 17 It means from Figure 16 The direction of arrow 201 is observed as an example of the magnetization direction of the returning magnetic pole, as shown in the model diagram.

[0143] Figure 18 It means from Figure 16 The direction of arrow 201 is observed in a model diagram of an example of the magnetization direction of the magnetization control layer.

[0144] Figure 19 It means from Figure 16 The diagram shows an example of the magnetization direction observed at the front end of the main magnetic pole, as indicated by arrow 201.

[0145] In the diagram, 203', 204', and 205' are arrows indicating the magnetization direction. 13 represents the ABS side.

[0146] In other examples of the magnetic heads used in the implementation, such as Figures 17-19 As shown, even after a demagnetization operation based on demagnetization is performed, the magnetization of the return magnetic pole 62a, the magnetization control layer 65-1, and the front end of the main magnetic pole 60 remains in the plane of the fabricated film in a state of disordered orientation. Therefore, a magnetoresistive effect is generated corresponding to the relative angle between the in-plane magnetization of the magnetization control layer 65-1 and the in-plane magnetization of the return magnetic pole 62a, and the resistance value will change due to the magnetization state after writing.

[0147] To suppress resistance deviation, for example, as in the magnetization control layer 65c of sample 12, a material with an absolute value of 0 to 0.2, such as FeCr, can be used instead of NiFe as the material for the magnetization control layer 65e.

[0148] Several embodiments of the present invention have been described, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These new embodiments can be implemented in a wide variety of other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

Claims

1. A magnetic head, characterized in that, include: Main magnetic pole; An auxiliary magnetic pole is provided with an open writing gap from the main magnetic pole; A spin torque control element is disposed in the write gap; A bias current control unit supplies bias current to the spin torque control element; and The resistance measuring unit measures the resistance value of the spin torque control element. The absolute difference between the first resistance value when the bias current is applied with the magnetization reversal polarity of the spin torque control element and the second resistance value when the bias current is applied with the opposite polarity is less than 4%. The spin torque control element includes a magnetization control layer and a non-magnetic conductive layer. When the thickness of the magnetization control layer is set to tF and the spin diffusion length is set to λF, then tF ≤ λF.

2. A magnetic head, characterized in that, include: Main magnetic pole; An auxiliary magnetic pole is provided with an open writing gap from the main magnetic pole; A spin torque control element is disposed in the write gap; A bias current control unit supplies bias current to the spin torque control element; and The resistance measuring unit measures the resistance value of the spin torque control element. The absolute difference between the first resistance value when the bias current is applied with the magnetization reversal polarity of the spin torque control element and the second resistance value when the bias current is applied with the opposite polarity is less than 4%. The spin torque control element includes a magnetization control layer and a non-magnetic conductive layer. When the thickness of the non-magnetic conductive layer is set to ts and the spin diffusion length is set to λs, then ts≥λs.

3. A magnetic head, characterized in that, include: Main magnetic pole; An auxiliary magnetic pole is provided with an open writing gap from the main magnetic pole; as well as A spin torque control element is disposed in the write gap. The absolute value of the magnetoresistive effect between the spin torque control element and the auxiliary magnetic pole, or between the spin torque control element and the main magnetic pole, is less than 4%. The spin torque control element includes a magnetization control layer and a non-magnetic conductive layer. When the thickness of the magnetization control layer is set to tF and the spin diffusion length is set to λF, then tF ≤ λF.

4. A magnetic head, characterized in that, include: Main magnetic pole; An auxiliary magnetic pole is provided with an open writing gap from the main magnetic pole; as well as A spin torque control element is disposed in the write gap. The absolute value of the magnetoresistive effect between the spin torque control element and the auxiliary magnetic pole, or between the spin torque control element and the main magnetic pole, is less than 4%. The spin torque control element includes a magnetization control layer and a non-magnetic conductive layer. When the thickness of the non-magnetic conductive layer is set to ts and the spin diffusion length is set to λs, then ts≥λs.

5. The magnetic head according to any one of claims 1 to 4, characterized in that, The absolute value of the spin polarization of the magnetization control layer is 0 to 0.

2.

6. The magnetic head according to any one of claims 1 to 4, characterized in that, The magnetization control layer is composed of an alloy material containing a first element and a second element, wherein the first element is at least one of iron, cobalt and nickel, and the second element is at least one of chromium, vanadium, manganese, titanium, scandium, molybdenum, palladium and iridium.

7. The magnetic head according to any one of claims 1 to 4, characterized in that, The magnetization control layer is composed of a stack of a first element and a second element, wherein the first element is at least one of iron, cobalt and nickel, and the second element is at least one of chromium, vanadium, manganese, titanium, scandium, molybdenum, palladium and iridium.

8. A magnetic recording and reproducing apparatus, characterized in that, The magnetic head is provided with any one of claims 1 to 4.

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