Magnetic recording device

Abstract

To provide a magnetic recording device capable of improving recording density.SOLUTION: A magnetic recording device 210 includes a magnetic head 110 and a control unit 75. The magnetic head includes a first magnetic pole 31, a second magnetic pole 32, a magnetic element 20 provided between the first magnetic pole and the second magnetic pole, a first terminal T1 electrically connected to the first magnetic pole, a second terminal T2 electrically connected to the second magnetic pole, and a coil 30c. The control unit is electrically connected to the first terminal, the second terminal, and the coil. One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit can perform a recording operation. In the recording operation, the control unit supplies a recording current to the coil while applying an element voltage of a first voltage or more and a second voltage or less between the first terminal and the second terminal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a magnetic recording device.

Background Art

[0002] Information is recorded on a magnetic recording medium such as a HDD (Hard Disk Drive) using a magnetic head. In a magnetic recording device, an improvement in recording density is desired.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Embodiments of the present invention provide a magnetic recording device capable of improving recording density.

Means for Solving the Problems

[0005] According to one embodiment, the magnetic recording device includes a magnetic head and a control unit. The magnetic head includes a first magnetic pole, a second magnetic pole, a magnetic element provided between the first and second magnetic poles, a first terminal electrically connected to the first magnetic pole, a second terminal electrically connected to the second magnetic pole, and a coil. The control unit is electrically connected to the first terminal, the second terminal, and the coil. One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit is capable of recording. In the recording operation, the control unit supplies a recording current to the coil while applying an element voltage between the first and second terminals that is between a first voltage and a second voltage. When the element voltage, the first voltage, and the second voltage are applied, the second potential of the second magnetic pole is lower than the first potential of the first magnetic pole. When the recording current is supplied to the coil and the positive applied voltage applied between the first and second terminals is changed, the differential resistance of the magnetic element reaches a first peak when the applied voltage is the first voltage. When the positive applied voltage is applied, the second potential is lower than the first potential. When the recording current is supplied to the coil and the first applied voltage is applied between the first and second terminals, a first signal is generated between the first and second terminals. The ratio of the absolute value of the difference between the first intensity of the first signal when the first applied voltage is a positive first value and the second intensity of the first signal when the first applied voltage is a negative second value, to the normalized rate of change, is 1 or less at the second voltage. The absolute value of the second value is the same as the first value. When the first applied voltage is positive, the second potential is lower than the first potential. When the first applied voltage is negative, the second potential is higher than the first potential. The normalized rate of change is the product of the absolute value of the rate of change of the second intensity with respect to the first applied voltage when the first applied voltage is negative, and the first voltage. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a schematic cross-sectional view illustrating a magnetic recording device according to the first embodiment. [Figure 2]Figure 2 is a schematic cross-sectional view illustrating a part of a magnetic recording device according to the first embodiment. [Figure 3] Figure 3 is a schematic plan view illustrating a part of the magnetic recording device according to the first embodiment. [Figure 4] Figures 4(a) and 4(b) are graphs illustrating the characteristics of a magnetic recording device according to the first embodiment. [Figure 5] Figure 5 is a graph illustrating the characteristics of a magnetic recording device according to the first embodiment. [Figure 6] Figure 6 is a graph illustrating the characteristics of a magnetic recording device according to the first embodiment. [Figure 7] Figure 7 is a graph illustrating the simulation results for a magnetic recording device. [Figure 8] Figure 8 is a graph illustrating the simulation results for a magnetic recording device. [Figure 9] Figures 9(a) to 9(d) are schematic diagrams illustrating the operation of the magnetic recording device according to the first embodiment. [Figure 10] Figure 10 is a schematic plan view illustrating a part of a magnetic recording device according to the second embodiment. [Figure 11] Figures 11(a) and 11(b) are graphs illustrating the characteristics of a magnetic recording device according to the second embodiment. [Figure 12] Figure 12 is a graph illustrating the characteristics of a magnetic recording device according to the second embodiment. [Figure 13] Figure 13 is a graph illustrating the characteristics of a magnetic recording device according to the second embodiment. [Figure 14] Figure 14 is a schematic plan view illustrating a part of a magnetic recording device according to the first embodiment. [Figure 15] Figure 15 is a schematic plan view illustrating a part of a magnetic recording device according to the first embodiment. [Figure 16] Figure 16 is a schematic perspective view illustrating a magnetic recording device according to an embodiment. [Figure 17] Figure 17 is a schematic perspective view illustrating a part of a magnetic recording apparatus according to an embodiment. [Figure 18] Figure 18 is a schematic perspective view illustrating a magnetic recording device according to an embodiment. [Figure 19] Figures 19(a) and 19(b) are schematic perspective views illustrating a part of a magnetic recording apparatus according to an embodiment. [Modes for carrying out the invention]

[0007] (First Embodiment) Figure 1 is a schematic cross-sectional view illustrating a magnetic recording device according to the first embodiment. As shown in Figure 1, the magnetic recording device 210 according to this embodiment includes a magnetic head 110 and a control unit 75. The magnetic recording device 210 may also include a magnetic recording medium 80. At least a recording operation is performed in the magnetic recording device 210. In the recording operation, information is recorded on the magnetic recording medium 80 using the magnetic head 110.

[0008] The magnetic head 110 includes a recording unit 60. As will be described later, the magnetic head 110 may also include a playback unit. The recording unit 60 includes a first magnetic pole 31, a second magnetic pole 32, a magnetic element 20, and a coil 30c. The magnetic element 20 is provided between the first magnetic pole 31 and the second magnetic pole 32.

[0009] For example, the first magnetic pole 31 and the second magnetic pole 32 form a magnetic circuit. The first magnetic pole 31 is, for example, a principal magnetic pole. The second magnetic pole 32 is, for example, a trailing shield. Alternatively, the first magnetic pole 31 may be a trailing shield and the second magnetic pole 32 may be a principal magnetic pole.

[0010] The direction from the magnetic recording medium 80 to the magnetic head 110 is defined as the Z-axis direction. One direction perpendicular to the Z-axis direction is defined as the X-axis direction. The direction perpendicular to both the Z-axis direction and the X-axis direction is defined as the Y-axis direction. The Z-axis direction corresponds to, for example, the height direction. The X-axis direction corresponds to, for example, the down-track direction. The Y-axis direction corresponds to, for example, the cross-track direction. Along the down-track direction, the magnetic recording medium 80 and the magnetic head 110 move relatively. A recording magnetic field generated from the magnetic head 110 is applied to a desired position on the magnetic recording medium 80. The magnetization of the desired position on the magnetic recording medium 80 is controlled in a direction corresponding to the recording magnetic field. Thereby, information is recorded on the magnetic recording medium 80.

[0011] The direction from the first magnetic pole 31 to the second magnetic pole 32 is defined as the first direction D1. The first direction D1 substantially follows the X-axis direction. In an embodiment, the first direction D1 may be inclined with respect to the X-axis direction. The angle of inclination is, for example, more than 0 degrees and 10 degrees or less.

[0012] In this example, a part of the coil 30c is between the first magnetic pole 31 and the second magnetic pole 32. In this example, a shield 33 is provided. In the X-axis direction, the first magnetic pole 31 is between the shield 33 and the second magnetic pole 32. Another part of the coil 30c is between the shield 33 and the first magnetic pole 31. An insulating portion 30i is provided between these multiple elements. The shield 33 is, for example, a leading shield. The magnetic head 110 may include a side shield (not shown).

[0013] As shown in FIG. 1, a recording current Iw is supplied from the recording circuit 30D to the coil 30c. For example, a first coil terminal Tc1 and a second coil terminal Tc2 are provided on the coil 30c. Through these coil terminals, the recording current Iw is supplied to the coil 30c. From the first magnetic pole 31, a recording magnetic field corresponding to the recording current Iw is applied to the magnetic recording medium 80.

[0014] As shown in Figure 1, the first magnetic pole 31 includes a medium-facing surface 30F. The medium-facing surface 30F is, for example, ABS (Air Bearing Surface). The medium-facing surface 30F faces, for example, a magnetic recording medium 80. The medium-facing surface 30F is, for example, aligned with the XY plane.

[0015] As shown in Figure 1, the element circuit 20D is electrically connected to the magnetic element 20. In this example, the magnetic element 20 is electrically connected to the first magnetic pole 31 and the second magnetic pole 32. The magnetic head 110 is provided with a first terminal T1 and a second terminal T2. The first terminal T1 is electrically connected to one end of the magnetic element 20 via the first wiring W1 and the first magnetic pole 31. The second terminal T2 is electrically connected to the other end of the magnetic element 20 via the second wiring W2 and the second magnetic pole 32. From the element circuit 20D, for example, an element current ic is supplied to the magnetic element 20.

[0016] As shown in Figure 1, the element current ic has a direction from the first magnetic pole 31 to the second magnetic pole 32. As shown in Figure 1, the electron flow je associated with the element current ic has a direction from the second magnetic pole 32 to the first magnetic pole 31. The element current ic is, for example, DC.

[0017] For example, when an element current ic exceeding a threshold flows through the magnetic element 20, oscillation occurs in the magnetic layer contained within the magnetic element 20. The magnetic element 20 functions, for example, as an STO (Spin-Torque Oscillator). Along with the oscillation, an alternating magnetic field (for example, a high-frequency magnetic field) is generated from the magnetic element 20. The alternating magnetic field generated by the magnetic element 20 is applied to the magnetic recording medium 80, assisting in recording to the magnetic recording medium 80. For example, MAMR (Microwave Assisted Magnetic Recording) can be performed.

[0018] The recording circuit 30D and the element circuit 20D are included in the control unit 75. The control unit 75 is electrically connected to the magnetic element 20 and the coil 30c. The control unit 75 is electrically connected to the first terminal T1, the second terminal T2 and the coil 30c. The control unit 75 can supply a recording current Iw to the coil 30c and an element current ic to the magnetic element 20.

[0019] For example, the control unit 75 (element circuit 20D) applies an element voltage V20 corresponding to the element current ic between the first terminal T1 and the second terminal T2. In practice, the element current ic may be controlled by controlling the element voltage V20. The element voltage V20 corresponds, for example, to the potential of the first terminal T1 with respect to the potential of the second terminal T2. The wiring resistance between these terminals and the magnetic element 20 is substantially constant. The voltage difference between the element voltage V20 and the voltage drop in the wiring is applied to the magnetic element 20. A change in the voltage applied to the magnetic element 20 corresponds to a change in the element voltage V20. For example, when considering the characteristics of the magnetic element 20 based on the applied voltage, the voltage applied between the first terminal T1 and the second terminal T2 (element voltage V20) may be considered to be substantially applied to the magnetic element 20. For example, the rate of change in the element voltage V20 is substantially the same as the rate of change in the voltage applied to the magnetic element 20.

[0020] As described above, during the recording operation, the control unit 75 applies an element voltage V20 between the first terminal T1 and the second terminal T2 while supplying a recording current Iw to the coil 30c. The element voltage V20 is greater than or equal to the first voltage V1 and less than or equal to the second voltage V2, as described later.

[0021] The element voltage V20 is positive. When the element voltage V20, the first voltage V1, and the second voltage V2 are applied, the second potential of the second magnetic pole 32 (the potential of the second terminal T2) is lower than the first potential of the first magnetic pole 31 (the potential of the first terminal T1).

[0022] The following describes an example of the magnetic head 110. Figure 2 is a schematic cross-sectional view illustrating a part of a magnetic recording device according to the first embodiment. Figure 3 is a schematic plan view illustrating a part of the magnetic recording device according to the first embodiment. As shown in Figures 2 and 3, the magnetic element 20 includes a first magnetic layer 21, a second magnetic layer 22, a third magnetic layer 23, and a fourth magnetic layer 24. The first magnetic layer 21 is provided between the first magnetic pole 31 and the second magnetic pole 32. The second magnetic layer 22 is provided between the first magnetic layer 21 and the second magnetic pole 32. The third magnetic layer 23 is provided between the second magnetic layer 22 and the second magnetic pole 32. The fourth magnetic layer 24 is provided between the third magnetic layer 23 and the second magnetic pole 32.

[0023] The magnetic element 20 includes a first non-magnetic layer 41, a second non-magnetic layer 42, a third non-magnetic layer 43, a fourth non-magnetic layer 44, and a fifth non-magnetic layer 45. The first non-magnetic layer 41 is provided between the first magnetic pole 31 and the first magnetic layer 21. The second non-magnetic layer 42 is provided between the first magnetic layer 21 and the second magnetic layer 22. The third non-magnetic layer 43 is provided between the second magnetic layer 22 and the third magnetic layer 23. The fourth non-magnetic layer 44 is provided between the third magnetic layer 23 and the fourth magnetic layer 24. The fifth non-magnetic layer 45 is provided between the fourth magnetic layer 24 and the second magnetic pole 32.

[0024] As shown in Figure 3, in the magnetic head 110, the first magnetic layer 21 and the third magnetic layer 23 are thicker than the second magnetic layer 22 and the fourth magnetic layer 24.

[0025] As already explained, the direction from the first magnetic pole 31 to the second magnetic pole 32 is the first direction D1. The thickness of the first magnetic layer 21 along the first direction D1 is defined as the first thickness t21. The thickness of the second magnetic layer 22 along the first direction D1 is defined as the second thickness t22. The thickness of the third magnetic layer 23 along the first direction D1 is defined as the third thickness t23. The thickness of the fourth magnetic layer 24 along the first direction D1 is defined as the fourth thickness t24.

[0026] In the magnetic head 110, the first thickness t21 is thicker than the second thickness t22. The first thickness t21 is thicker than the fourth thickness t24. The third thickness t23 is thicker than the second thickness t22. The third thickness t23 is thicker than the fourth thickness t24.

[0027] The following describes examples of the characteristics of the magnetic head 110. Figures 4(a) and 4(b) are graphs illustrating the characteristics of a magnetic recording device according to the first embodiment. The horizontal axis in these figures represents the applied voltage Vap. The applied voltage Vap is the voltage applied between the first terminal T1 and the second terminal T2 while the recording current Iw is supplied to the coil 30c. When a positive applied voltage Vap is applied, the second potential of the second magnetic pole 32 is lower than the first potential of the first magnetic pole 31.

[0028] The vertical axis in Figure 4(a) represents the electrical resistance Rv1 of the magnetic element 20. Electrical resistance Rv1 corresponds to the electrical resistance between the first terminal T1 and the second terminal T2. The vertical axis in Figure 4(b) represents the differential resistance Rd1.

[0029] As shown in Figure 4(a), when the applied voltage Vap is positive, the electrical resistance Rv1 increases as the applied voltage Vap increases. The increase in electrical resistance Rv1 includes the effect of heat caused by the applied voltage Vap. When the applied voltage Vap is the first voltage V1, the electrical resistance Rv1 changes discontinuously.

[0030] As shown in Figure 4(b), when the applied voltage Vap is the first voltage V1, the differential resistance Rd1 has a first peak Pd1. The first peak Pd1 corresponds to a discontinuous change in the electrical resistance Rv1.

[0031] As will be described later, the discontinuous change in electrical resistance Rv1 at the first voltage V1, and the first peak Pd1, are thought to be due to the reversal of magnetization of the magnetic layer contained in the magnetic element 20.

[0032] Thus, when the recording current Iw is supplied to the coil 30c and the positive applied voltage Vap applied between the first terminal T1 and the second terminal T2 is changed, the differential resistance Rd1 of the magnetic element 20 reaches a first peak Pd1 when the applied voltage Vap is the first voltage V1.

[0033] As shown in Figure 4(a), when the applied voltage Vap is negative, there may be a voltage at which the electrical resistance Rv1 changes discontinuously when the absolute value of the applied voltage Vap is increased. As shown in Figure 4(b), when the applied voltage Vap is negative, there may be a voltage at which the differential resistance Rd1 has a local peak when the absolute value of the applied voltage Vap is increased. As shown in Figure 4(b), when the applied voltage Vap is positive, there may be a local peak (dashed line) in the differential resistance Rd1 when the applied voltage Vap is excessively high (voltage Vp2 exceeding the second voltage V2).

[0034] At a voltage of V1 or higher, as illustrated in Figure 4(b), the magnetization of the magnetic layer contained in the magnetic element 20 is reversed, and an alternating magnetic field is generated from the magnetic element 20.

[0035] In the embodiment, it was found that when a voltage is applied between the first terminal T1 and the second terminal T2, an electrical signal is observed between the first terminal T1 and the second terminal T2. This electrical signal is different from DC. This electrical signal is thought to be related to fluctuations in electrical resistance occurring within the magnetic element 20. This electrical signal is thought to be related, for example, to fluctuations in the magnetization of the magnetic layer contained in the magnetic element 20. This electrical signal is thought to include noise that generally appears during electrical measurements. This electrical signal is thought to include, for example, noise due to the effects of heat.

[0036] The following explains the example of the electrical signal mentioned above. Figure 5 is a graph illustrating the characteristics of a magnetic recording device according to the first embodiment. The horizontal axis in Figure 5 represents the absolute value of the first applied voltage Va1. The horizontal axis in Figure 6 is displayed in a normalized form. The first applied voltage Va1 is the voltage applied between the first terminal T1 and the second terminal T2 while the recording current Iw is supplied to the coil 30c. The first applied voltage Va1 can be positive or negative. When the first applied voltage Va1 is positive, the second potential is lower than the first potential. When the first applied voltage Va1 is negative, the second potential is higher than the first potential.

[0037] When a recording current Iw is supplied to coil 30c and a first applied voltage Va1 is applied between the first terminal T1 and the second terminal T2, a first signal Sg1 is generated between the first terminal T1 and the second terminal T2.

[0038] The vertical axis in Figure 5 represents the magnitude of the first signal Sg1. In Figure 5, the intensity Sp1 of the first signal Sg1 when the first applied voltage Va1 is positive is shown by a solid line. In Figure 5, the intensity Sn1 of the first signal Sg1 when the first applied voltage Va1 is negative is shown by a dashed line. In this example, the first signal Sg1 has a 1.25 GHz component.

[0039] As shown in Figure 5, when the first applied voltage Va1 is negative and its absolute value is greater than the first voltage V1, the rate of change of the intensity Sn1 of the first signal Sg1 with respect to the first applied voltage Va1 is substantially constant. That is, when the first applied voltage Va1 is negative, the intensity Sn1 of the first signal Sg1 changes substantially linearly. In contrast, when the first applied voltage Va1 is positive, the rate of change of the intensity Sp1 of the first signal Sg1 with respect to the first applied voltage Va1 is not constant. In this example, the rate of change is low in the first voltage range Vr1 where the first applied voltage Va1 is approximately 3.2 or less. The rate of change is high in the second voltage range Vr2 where the first applied voltage Va1 is greater than approximately 3.2.

[0040] Such characteristics when the first applied voltage Va1 is positive are thought to reflect the magnetization state contained in the magnetic layer of the magnetic element 20. By deriving the difference between the characteristics when the first applied voltage Va1 is positive and the characteristics when the first applied voltage Va1 is negative, the uniqueness of the characteristics when the first applied voltage Va1 is positive becomes clearer. For example, the effects of noise that commonly appear during electrical measurements can be eliminated.

[0041] As shown in Figure 5, the intensity Sp1 of the first signal Sg1 when the first applied voltage Va1 is a positive first value Vv1 is defined as the first intensity Sv1. The intensity Sn1 of the first signal Sg1 when the first applied voltage Va1 is a negative second value Vv2 is defined as the second intensity Sv2. The absolute value of the second value Vv2 is the same as the absolute value of the first value Vv1. The difference between the first intensity Sv1 and the second intensity Sv2 is defined as the difference ΔSg1.

[0042] As shown in Figure 5, when the first applied voltage Va1 changes from the first voltage range Vr1 to the second voltage range Vr2, the difference ΔSg1 increases rapidly.

[0043] Figure 6 is a graph illustrating the characteristics of a magnetic recording device according to the first embodiment. The horizontal axis in Figure 6 represents the absolute value of the first applied voltage Va1. The horizontal axis in Figure 6 is displayed in a normalized form. The vertical axis represents the parameter P1. Parameter P1 is the ratio of the absolute value of the difference ΔSg between the first intensity Sv1 and the second intensity Sv2 to the normalized rate of change. As already explained, the first intensity Sv1 is the intensity Sp1 of the first signal Sg1 when the first applied voltage Va1 is a positive first value Vv1. The second intensity Sv2 is the intensity Sn1 of the first signal Sg1 when the first applied voltage Va1 is a negative second value Vv2. The absolute value of the second value Vv2 is the same as the first value Vv1. The normalized rate of change is the product of the absolute value of the rate of change of the second intensity Sv2 with respect to the first applied voltage Va1 when the first applied voltage Va1 is negative, and the first voltage V1. The rate of change of the second intensity Sv2 with respect to the first applied voltage Va1 is calculated in the region where the absolute value of the first applied voltage Va1 is higher than that of the first voltage V1. The normalized rate of change corresponds to the absolute value of the rate of change of the second intensity Sv2 with respect to the first applied voltage Va1 normalized by the first voltage V1. Parameter P1 corresponds to the value normalized by the rate of change (slope) of the first signal Sg1 when the first applied voltage Va1 is negative.

[0044] As shown in Figure 6, the parameter P1 (ratio) increases gradually in response to changes in the first applied voltage Va1 when the first applied voltage Va1 is between 1 and approximately 3.2 (between 1 and approximately 3.3 times the first voltage V1). When the first applied voltage Va1 exceeds approximately 3.2, the parameter P1 increases rapidly in response to changes in the first applied voltage Va1.

[0045] As shown in Figure 6, in this embodiment, the second voltage V2 is set to approximately 3.2 in Figure 6. That is, parameter P1 is 1 or less at the second voltage V2. In this embodiment, the element voltage V20 is set to be less than or equal to this second voltage V2. This is expected to provide a stable alternating magnetic field. For example, stable MAMR can be implemented. A magnetic recording device that can improve recording density can be provided.

[0046] For example, in the first voltage range Vr1 where the first applied voltage Va1 is between the first voltage V1 and the second voltage V2, the magnetization of the multiple magnetic layers contained in the magnetic element 20 is considered to be moving stably. For example, synchronized precession is considered to be occurring stably. In the second voltage range Vr2, which exceeds the second voltage V2, the synchronization of the magnetization of the multiple magnetic layers contained in the magnetic element 20 is considered to be disrupted.

[0047] As shown in Figure 6, the parameter P1 increases monotonically with increasing absolute value of the first applied voltage Va1. The absolute value of the difference ΔSg1 (see Figure 5) also increases monotonically with increasing absolute value of the first applied voltage Va1.

[0048] The frequency of the first signal Sg1 described above is, for example, between 10 Hz and 3 GHz. In the example in Figure 5, a 1.25 GHz component is shown as the first signal Sg1. Similar characteristics to those in Figure 5 can be obtained at frequencies between 10 Hz and 3 GHz. For example, similar characteristics to those in Figure 5 can be obtained when integrating in any frequency range between 10 Hz and 3 GHz.

[0049] The first signal Sg1 described above is obtained, for example, by measuring the electrical signal at the first terminal T1 or the second terminal T2 with a spectrum analyzer. The magnitude of the signal is measured, for example, in dBm. In the measurement, it is preferable that frequencies used for information communication (e.g., frequencies in which radio waves exist in space) are not used. In the measurement, it is preferable that the frequency of the AC power supply (e.g., 50 Hz or 60 Hz) is not used. For example, the integration of any frequency range from 10 Hz to 3 GHz is obtained, for example, by adding the measured values ​​from a spectrum analyzer. The integrated value may be measured by a power meter. In the integration, for example, it is preferable that the value of frequencies used for information communication (e.g., frequencies in which radio waves exist in space) is excluded. In the integration, it is preferable that the value of the frequency of the AC power supply (e.g., 50 Hz or 60 Hz) is excluded. For example, the measurement may include signal amplification.

[0050] The frequency of this first signal Sg1 is defined as the first frequency. As described above, an alternating magnetic field is generated from the magnetic element 20 during the recording operation. The frequency of the alternating magnetic field is defined as the second frequency. The first frequency is lower than the second frequency. The second frequency is, for example, between 10 GHz and 50 GHz.

[0051] As shown in Figure 4(b), in the magnetic head 110, the differential resistance Rd1 has no peaks other than the first peak Pd1 between the first voltage V1 and the second voltage V2.

[0052] The following describes an example of simulation results for the magnetic head 110. Figure 7 is a graph illustrating the simulation results for a magnetic recording device. The vertical axis in Figure 7 represents the first applied voltage Va1. The vertical axis represents the intensity Is of the first frequency component of the signal generated between the first terminal T1 and the second terminal T2. In this example, the first frequency is 0.2 GHz.

[0053] As shown in Figure 7, the first applied voltage Va1 includes a first voltage range Vr1, a second voltage range Vr2, and a third voltage range Vr3. The third voltage range Vr3 is lower than the first voltage V1. The second voltage range Vr2 is between the first voltage V1 and the second voltage V2. The second voltage range Vr2 exceeds the second voltage V2.

[0054] The rate of change of intensity Is in response to a change in the first applied voltage Va1 is the first rate of change RT1 in the first voltage range Vr1. The rate of change is the second rate of change RT2 in the second voltage range Vr2. The rate of change is the third rate of change RT3 in the third voltage range Vr3. The first rate of change RT1 is lower than the second rate of change RT2 and higher than the third rate of change RT3.

[0055] The simulation results in Figure 7 correspond to the intensity Sp1 (solid line) of the first signal Sg1 when the first applied voltage Va1 is positive, as shown in Figure 5. The simulation results in Figure 7 illustrate the influence of the magnetization state. The simulation results in Figure 7 are thought to correspond to characteristics obtained by removing the effects of heat, etc., from actual measurement results, for example. In Figure 6 above, it is thought that the effects of heat, etc., are removed by deriving the difference between the characteristics when the first applied voltage Va1 is positive and the characteristics when the first applied voltage Va1 is negative.

[0056] Figure 8 is a graph illustrating the simulation results for a magnetic recording device. Figure 8 illustrates the simulation results for the oscillation frequency fr21 of the first magnetic layer 21 and the oscillation frequency fr23 of the third magnetic layer 23. The horizontal axis of Figure 8 represents the positive first applied voltage Va1. The vertical axis represents the oscillation frequency fr0 of the magnetization of these magnetic layers. Frequency fr0 corresponds to the first frequency of the alternating magnetic field.

[0057] When the first applied voltage Va1 is lower than the first voltage V1 shown in Figure 8 (third voltage range Vr3), oscillation does not substantially occur. Oscillation occurs when the first applied voltage Va1 is higher than the first voltage V1.

[0058] When the first applied voltage Va1 is between the first voltage V1 and the second voltage V2 (first voltage range Vr1), the oscillation frequency fr21 coincides with the oscillation frequency fr23. This state corresponds to a state in which the magnetization of the first magnetic layer 21 and the magnetization of the third magnetic layer 23 are oscillating in synchronous motion with opposite phases.

[0059] When the first applied voltage Va1 exceeds the second voltage V2 (second voltage range Vr2), a difference occurs between the oscillation frequency fr21 and the oscillation frequency fr23. When the first applied voltage Va1 exceeds the second voltage V2, the oscillations in the first magnetic layer 21 and the third magnetic layer 23 are not in opposite phase.

[0060] In this embodiment, the first voltage V1 is thought to correspond to the threshold voltage (lowest voltage) at which the magnetization oscillates. The second voltage V2 is thought to correspond to the highest voltage at which multiple magnetizations oscillate stably in synchronous, opposite-phase manner.

[0061] By applying an element voltage V20 within this range, stable operation can be achieved. According to this embodiment, a magnetic recording device capable of improving recording density can be provided.

[0062] In the magnetic head 110, the first magnetic layer 21 and the third magnetic layer 23 are, for example, oscillation layers. The second magnetic layer 22 and the fourth magnetic layer 24 are, for example, spin injection layers.

[0063] In the magnetic head 110, for example, the first non-magnetic layer 41 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The second non-magnetic layer 42 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The third non-magnetic layer 43 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The fourth non-magnetic layer 44 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The fifth non-magnetic layer 45 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0064] In a first material comprising at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W, spins are poorly permeable. In a second material comprising at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag, spins are easily permeable.

[0065] In the magnetic head 110, the resulting electrical signals (such as the differential resistance Rd1 and the first signal Sg1) are thought to correspond to changes in the magnetization state of the magnetic layer. Examples of magnetization states are described below.

[0066] Figures 9(a) to 9(d) are schematic diagrams illustrating the operation of the magnetic recording device according to the first embodiment. In the first state ST1 shown in Figure 9(a), the first applied voltage Va1 is in the third voltage range Vr3. As shown in Figure 9(a), in one example, in the first state ST1, the magnetization 31M of the first magnetic pole 31 and the magnetization 32M of the second magnetic pole 32 are "upward". "Upward" corresponds to the direction from the second magnetic pole 32 to the first magnetic pole 31. In the first state ST1, the magnetization 21M of the first magnetic layer 21, the magnetization 22M of the second magnetic layer 22, the magnetization 23M of the third magnetic layer 23, and the magnetization 24M of the fourth magnetic layer 24 are "upward". "Upward" corresponds to the direction from the second magnetic pole 32 to the first magnetic pole 31. In the examples in Figures 9(a) to 9(d), the direction (polarity) of the recording current Iw corresponds to the "upward" direction.

[0067] As shown in Figure 9(b), when the first applied voltage Va1 is the first voltage V1, the magnetization 24M of the fourth magnetic layer 24 is reversed.

[0068] In the second state ST2 shown in Figure 9(c), the first applied voltage Va1 is within the first voltage range Vr1. As shown in Figure 9(c), in the second state ST2, the magnetization 21M of the first magnetic layer 21 and the magnetization 23M of the third magnetic layer 23 oscillate. This generates an alternating magnetic field from the magnetic element 20. The magnetizations 21M and 23M oscillate in opposite phases. For example, the phase difference between the Y-axis component of magnetization 21M and the Y-axis component of magnetization 23M is between 160 degrees and 200 degrees. In the second state ST2, a stable oscillation frequency can be obtained due to the opposite-phase oscillation. Appropriate MAMR can be performed. In the second state ST2, due to the synchronous oscillation in opposite phases, the noise signal (first frequency) is small and the rate of change of intensity Is is considered to be low.

[0069] In the third state ST3 shown in Figure 9(d), the first applied voltage Va1 is within the second voltage range Vr2. As shown in Figure 9(d), in the third state ST3, the magnetization 21M of the first magnetic layer 21 and the magnetization 23M of the third magnetic layer 23 oscillate. In the third state ST3, the oscillations in these magnetic layers are not in opposite phase. For example, the oscillation frequency of magnetization 21M is different from the oscillation frequency of magnetization 23M. In the third state ST3, proper MAMR is difficult due to the oscillations that are not in opposite phase. In the third state ST3, a noise signal (first frequency) corresponding to the difference between multiple oscillations that are not in opposite phase is generated, and the rate of change of intensity Is is considered to be high. For example, the oscillation frequencies of magnetization 21M and magnetization 23M fluctuate. In the third state ST3, a noise signal (first frequency) is generated due to the oscillations that are not in opposite phase, and the rate of change of intensity Is is considered to be high.

[0070] (Second Embodiment) Figure 10 is a schematic plan view illustrating a part of a magnetic recording device according to the second embodiment. As shown in Figure 10, the configuration of the magnetic head 111 according to the second embodiment differs from the configuration of the magnetic head 110 described above.

[0071] In the magnetic head 111, the magnetic element 20 includes a first magnetic layer 21, a second magnetic layer 22, a third magnetic layer 23, and a fourth magnetic layer 24. The first magnetic layer 21 is provided between the first magnetic pole 31 and the second magnetic pole 32. The second magnetic layer 22 is provided between the first magnetic layer 21 and the second magnetic pole 32. The third magnetic layer 23 is provided between the second magnetic layer 22 and the second magnetic pole 32. The fourth magnetic layer 24 is provided between the third magnetic layer 23 and the second magnetic pole 32.

[0072] In the magnetic head 111, the first thickness t21 of the first magnetic layer 21 along the first direction D1 from the first magnetic pole 31 to the second magnetic pole 32 is thicker than the second thickness t22 of the second magnetic layer 22 along the first direction D1, and thicker than the fourth thickness t24 of the fourth magnetic layer 24 along the first direction D1. The third thickness t23 of the third magnetic layer 23 along the first direction D1 is thicker than the second thickness t22, and thicker than the fourth thickness t24.

[0073] The configuration of the magnetic recording device according to the second embodiment may be the same as that of the magnetic recording device 210 described above. That is, in the magnetic recording device 210 according to the second embodiment, the control unit 75 supplies a recording current Iw to the coil 30c while applying an element voltage V20 between the first terminal T1 and the second terminal T2, which is between a first voltage V1 and a second voltage V2, during the recording operation. When the element voltage V20, the first voltage V1 and the second voltage V2 are applied, the second potential of the second magnetic pole 32 is lower than the first potential of the first magnetic pole 31.

[0074] The electrical resistance characteristics of the magnetic head 111 according to the second embodiment are different from those of the magnetic head 110.

[0075] Figures 11(a) and 11(b) are graphs illustrating the characteristics of a magnetic recording device according to the second embodiment. The horizontal axis in these figures represents the applied voltage Vap. The applied voltage Vap is the voltage applied between the first terminal T1 and the second terminal T2 while the recording current Iw is supplied to the coil 30c. When a positive applied voltage Vap is applied, the second potential of the second magnetic pole 32 is lower than the first potential of the first magnetic pole 31.

[0076] The vertical axis in Figure 11(a) represents the electrical resistance Rv1 of the magnetic element 20. Electrical resistance Rv1 corresponds to the electrical resistance between the first terminal T1 and the second terminal T2. The vertical axis in Figure 11(b) represents the differential resistance Rd1.

[0077] As shown in Figure 11(a), when the applied voltage Vap is positive, the electrical resistance Rv1 increases as the applied voltage Vap increases. The increase in electrical resistance Rv1 includes the effect of heat caused by the applied voltage Vap. When the applied voltage Vap is the first voltage V1, the electrical resistance Rv1 changes discontinuously. When the applied voltage Vap is the third voltage V3, the electrical resistance Rv1 changes discontinuously.

[0078] As shown in Figure 11(b), when the applied voltage Vap is the first voltage V1, the differential resistance Rd1 has a first peak Pd1. The first peak Pd1 corresponds to a discontinuous change in the electrical resistance Rv1. The differential resistance Rd1 has a second peak Pd2 when the positive applied voltage Vap is the third voltage V3. The third voltage V3 is higher than the first voltage V1 and lower than the second voltage V2. In this case as well, when a positive applied voltage Vap is applied, the second potential of the second terminal T2 is lower than the first potential of the first terminal T1.

[0079] As shown in Figure 11(b), when the applied voltage Vap is negative, it is not necessary for there to be a voltage at which the differential resistance Rd1 has a local peak when the absolute value of the applied voltage Vap is increased.

[0080] Figure 12 is a graph illustrating the characteristics of a magnetic recording device according to the second embodiment. The horizontal axis in Figure 12 represents the absolute value of the first applied voltage Va1. The horizontal axis in Figure 12 is displayed in a normalized form. The first applied voltage Va1 is the voltage applied between the first terminal T1 and the second terminal T2 while the recording current Iw is supplied to the coil 30c. The first applied voltage Va1 can be positive or negative. When the first applied voltage Va1 is positive, the second potential is lower than the first potential. When the first applied voltage Va1 is negative, the second potential is higher than the first potential.

[0081] When a recording current Iw is supplied to coil 30c and a first applied voltage Va1 is applied between the first terminal T1 and the second terminal T2, a first signal Sg1 is generated between the first terminal T1 and the second terminal T2.

[0082] The vertical axis in Figure 12 represents the magnitude of the first signal Sg1. In Figure 12, the intensity Sp1 of the first signal Sg1 when the first applied voltage Va1 is positive is shown by a solid line. In Figure 12, the intensity Sn1 of the first signal Sg1 when the first applied voltage Va1 is negative is shown by a dashed line. In this example, the first signal Sg1 has a 1.25 GHz component.

[0083] As shown in Figure 12, when the first applied voltage Va1 is negative, the rate of change of the intensity Sn1 of the first signal Sg1 with respect to the first applied voltage Va1 is substantially constant. That is, when the first applied voltage Va1 is negative, the intensity Sn1 of the first signal Sg1 changes substantially linearly. In contrast, when the first applied voltage Va1 is positive, the rate of change of the intensity Sp1 of the first signal Sg1 with respect to the first applied voltage Va1 is not constant. In this example, the rate of change is low in the first voltage range Vr1 where the first applied voltage Va1 is approximately 4.4 or less. The rate of change is high in the second voltage range Vr2 where the first applied voltage Va1 is greater than approximately 4.4.

[0084] Figure 13 is a graph illustrating the characteristics of a magnetic recording device according to the second embodiment. The horizontal axis in Figure 13 represents the absolute value of the first applied voltage Va1. The horizontal axis in Figure 13 is displayed in a normalized form. The vertical axis represents the parameter P1. Parameter P1 is the ratio of the absolute value of the difference ΔSg between the first intensity Sv1 and the second intensity Sv2 to the normalized rate of change. As already explained, the first intensity Sv1 is the intensity Sp1 of the first signal Sg1 when the first applied voltage Va1 is a positive first value Vv1. The second intensity Sv2 is the intensity Sn1 of the first signal Sg1 when the first applied voltage Va1 is a negative second value Vv2. The absolute value of the second value Vv2 is the same as the first value Vv1. The normalized rate of change is the product of the absolute value of the rate of change of the second intensity Sv2 with respect to the first applied voltage Va1 when the first applied voltage Va1 is negative, and the first voltage V1. The rate of change of the second intensity Sv2 with respect to the first applied voltage Va1 is calculated in the region where the absolute value of the first applied voltage Va1 is higher than that of the first voltage V1. The normalized rate of change corresponds to the absolute value of the rate of change of the second intensity Sv2 with respect to the first applied voltage Va1 normalized by the first voltage V1. Parameter P1 corresponds to the value normalized by the rate of change (slope) of the first signal Sg1 when the first applied voltage Va1 is negative.

[0085] As shown in Figure 13, the parameter P1 (ratio) increases gradually in response to changes in the first applied voltage Va1 when the first applied voltage Va1 is between 1 and approximately 4.4 (between 1 and approximately 4.4 times the first voltage V1). When the first applied voltage Va1 exceeds approximately 4.4, the parameter P1 increases rapidly in response to changes in the first applied voltage Va1.

[0086] As shown in Figure 13, in this embodiment, the second voltage V2 is set to approximately 4.4 in Figure 13. That is, parameter P1 is 5 or less at the second voltage V2. In this embodiment, the element voltage V20 is set to such a second voltage V2 or less. This is expected to provide a stable alternating magnetic field. For example, stable MAMR can be implemented. A magnetic recording device that can improve recording density can be provided.

[0087] In the magnetic head 111, the absolute value of the above difference ΔSg increases monotonically with increasing absolute value of the first applied voltage Va1 (see Figure 12).

[0088] In the magnetic head 111, the frequency of the first signal Sg1 is, for example, between 10 Hz and 3 GHz.

[0089] In the magnetic head 111, for example, the differential resistor Rd1 has no peaks other than the first peak Pd1 and the second peak Pd2 between the third voltage V3 and the second voltage V2.

[0090] In the magnetic head 111, the intensity of the first signal Sg1 also changes with the voltage range, similar to the magnetic head 110 (see Figure 7). For example, when the first applied voltage Va1 is positive, the intensity of the first frequency component of the first signal Sg1 changes in accordance with the change in the first applied voltage Va1. The first frequency is, for example, 10 Hz or more and 3 GHz or less. The first applied voltage Va1 includes a first voltage range Vr1 between the first voltage V1 and the second voltage V2, a second voltage range Vr2 above the second voltage V2, and a third voltage range Vr3 below the first voltage V1 (see Figure 7). The rate of change of the intensity of the first signal Sg1 in response to the change in the first applied voltage Va1 is the first rate of change RT1 in the first voltage range Vr1. The rate of change is the second rate of change RT2 in the second voltage range Vr2. The rate of change is the third rate of change RT3 in the third voltage range Vr3.

[0091] In one embodiment, the second rate of change RT2 is higher than the first rate of change RT1. This allows for stable MAMR to be performed. In another embodiment, for example, the third rate of change RT3 is lower than the first rate of change RT1.

[0092] In the magnetic head 111, for example, during recording, a second frequency signal is generated from the magnetic element 20. The second frequency is, for example, between 10 GHz and 50 GHz.

[0093] In the magnetic head 111, the first non-magnetic layer 41 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The second non-magnetic layer 42 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The third non-magnetic layer 43 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The fourth non-magnetic layer 44 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The fifth non-magnetic layer 45 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0094] (Third embodiment) Figure 14 is a schematic plan view illustrating a part of a magnetic recording device according to the first embodiment. As shown in Figure 14, in the magnetic head 112 according to the embodiment, the magnetic element 20 also includes a first magnetic layer 21, a second magnetic layer 22, a third magnetic layer 23, and a fourth magnetic layer 24. In the magnetic head 112, the first thickness t21 is thicker than the second thickness t22. The first thickness t21 is thicker than the third thickness t23. The fourth thickness t24 is thicker than the second thickness t22. The fourth thickness t24 is thicker than the third thickness t23. In the magnetic head 112, the first magnetic layer 21 and the fourth magnetic layer 24 are, for example, oscillation layers. The second magnetic layer 22 and the third magnetic layer 23 are, for example, spin injection layers.

[0095] In the magnetic head 112, the magnetic element 20 includes a first non-magnetic layer 41, a second non-magnetic layer 42, a third non-magnetic layer 43, a fourth non-magnetic layer 44, and a fifth non-magnetic layer 45. In the magnetic head 112, the first non-magnetic layer 41 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The second non-magnetic layer 42 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The third non-magnetic layer 43 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The fourth non-magnetic layer 44 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The fifth non-magnetic layer 45 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0096] Even in such a magnetic head 112, the element voltage V20 during recording operation is within the first voltage range Vr1.

[0097] In the magnetic head 112, the second rate of change RT2 in the second voltage range Vr2 is higher than the first rate of change RT1 in the first voltage range Vr1. This allows for stable MAMR. In the magnetic head 112, for example, the third rate of change RT3 in the third voltage range Vr3 is lower than the first rate of change RT1.

[0098] Figure 15 is a schematic plan view illustrating a part of a magnetic recording device according to the first embodiment. As shown in Figure 15, in the magnetic head 113 according to the embodiment, the magnetic element 20 includes a first magnetic layer 21, a second magnetic layer 22, and a third magnetic layer 23. The first magnetic layer 21 is provided between the first magnetic pole 31 and the second magnetic pole 32. The second magnetic layer 22 is provided between the first magnetic layer 21 and the second magnetic pole 32. The third magnetic layer 23 is provided between the second magnetic layer 22 and the second magnetic pole 32. The direction from the first magnetic pole 31 to the second magnetic pole 32 is defined as the first direction D1. The first thickness t21 of the first magnetic layer 21 along the first direction D1 is greater than the third thickness t23 of the third magnetic layer 23 along the first direction D1. The second thickness t22 of the second magnetic layer 22 along the first direction D1 is greater than the third thickness t23. In the magnetic head 113, the first magnetic layer 21 and the second magnetic layer 22 are, for example, oscillation layers. The third magnetic layer 23 is, for example, a spin injection layer.

[0099] In the magnetic head 113, the magnetic element 20 includes a first non-magnetic layer 41, a second non-magnetic layer 42, a third non-magnetic layer 43, and a fourth non-magnetic layer 44. The first non-magnetic layer 41 is provided between the first magnetic pole 31 and the first magnetic layer 21. The second non-magnetic layer 42 is provided between the first magnetic layer 21 and the second magnetic layer 22. The third non-magnetic layer 43 is provided between the second magnetic layer 22 and the third magnetic layer 23. The fourth non-magnetic layer 44 is provided between the third magnetic layer 23 and the second magnetic pole 32.

[0100] In the magnetic head 113, the first non-magnetic layer 41 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The second non-magnetic layer 42 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The third non-magnetic layer 43 includes at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The fourth non-magnetic layer 44 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0101] Even in such a magnetic head 113, the element voltage V20 during recording operation is within the first voltage range Vr1.

[0102] In the magnetic head 113, the second rate of change RT2 in the second voltage range Vr2 is higher than the first rate of change RT1 in the first voltage range Vr1. This allows for stable MAMR. In the magnetic head 113, for example, the third rate of change RT3 in the third voltage range Vr3 is lower than the first rate of change RT1.

[0103] In magnetic heads 110 to 113, the thickness t41 of the first non-magnetic layer 41 is, for example, 5 nm to 15 nm. The thickness t42 of the second non-magnetic layer 42 is, for example, 5 nm to 15 nm. The thickness t43 of the third non-magnetic layer 43 is, for example, 5 nm to 15 nm. The thickness t44 of the fourth non-magnetic layer 44 is, for example, 5 nm to 15 nm. The thickness t45 of the fifth non-magnetic layer 45 is, for example, 5 nm to 15 nm.

[0104] The following describes examples of other configurations of the magnetic recording device according to the embodiment.

[0105] Figure 16 is a schematic perspective view illustrating a magnetic recording device according to an embodiment. As shown in Figure 16, the magnetic head according to the embodiment (for example, magnetic head 110) is used together with a magnetic recording medium 80. In this example, the magnetic head 110 includes a recording unit 60 and a playback unit 70. The recording unit 60 of the magnetic head 110 records information on the magnetic recording medium 80. The playback unit 70 reproduces the information recorded on the magnetic recording medium 80.

[0106] The magnetic recording medium 80 includes, for example, a media substrate 82 and a magnetic recording layer 81 provided on the media substrate 82. The magnetization 83 of the magnetic recording layer 81 is controlled by the recording unit 60.

[0107] The regeneration unit 70 includes, for example, a first regeneration magnetic shield 72a, a second regeneration magnetic shield 72b, and a magnetic regeneration element 71. The magnetic regeneration element 71 is provided between the first regeneration magnetic shield 72a and the second regeneration magnetic shield 72b. The magnetic regeneration element 71 is capable of outputting a signal corresponding to the magnetization 83 of the magnetic recording layer 81.

[0108] As shown in Figure 16, the magnetic recording medium 80 moves relative to the magnetic head 110 in the direction of the medium movement direction 85. The magnetic head 110 controls the information corresponding to the magnetization 83 of the magnetic recording layer 81 at any position. The magnetic head 110 reproduces the information corresponding to the magnetization 83 of the magnetic recording layer 81 at any position.

[0109] Figure 17 is a schematic perspective view illustrating a part of a magnetic recording apparatus according to an embodiment. Figure 17 illustrates a head slider. The magnetic head 110 is mounted on a head slider 159. The head slider 159 includes, for example, Al2O3 / TiC. The head slider 159 moves relative to the magnetic recording medium, either floating above or in contact with it.

[0110] The head slider 159 has, for example, an air inlet side 159A and an air outlet side 159B. The magnetic head 110 is positioned on the side of the air outlet side 159B of the head slider 159. As a result, the magnetic head 110 moves relative to the magnetic recording medium while floating above or in contact with it.

[0111] Figure 18 is a schematic perspective view illustrating a magnetic recording device according to an embodiment. Figures 19(a) and 19(b) are schematic perspective views illustrating a part of a magnetic recording apparatus according to an embodiment. As shown in Figure 18, a rotary actuator is used in the magnetic recording device 150 according to this embodiment. The recording medium disk 180 is mounted on a spindle motor 180M. The recording medium disk 180 rotates in the direction of arrow AR by the spindle motor 180M. The spindle motor 180M responds to a control signal from the drive unit control. The magnetic recording device 150 according to this embodiment may include a plurality of recording medium disks 180. The magnetic recording device 150 may also include a recording medium 181. The recording medium 181 is, for example, an SSD (Solid State Drive). For example, a non-volatile memory such as flash memory is used for the recording medium 181. For example, the magnetic recording device 150 may also be a hybrid HDD (Hard Disk Drive).

[0112] The head slider 159 records and plays back information to be recorded on the recording medium disk 180. The head slider 159 is located at the tip of a thin-film suspension 154. A magnetic head according to this embodiment is located near the tip of the head slider 159.

[0113] As the recording medium disk 180 rotates, the pressing pressure from the suspension 154 and the pressure generated on the media-facing surface (ABS) of the head slider 159 are balanced. The distance between the media-facing surface of the head slider 159 and the surface of the recording medium disk 180 becomes a predetermined amount of levitation. In this embodiment, the head slider 159 may be in contact with the recording medium disk 180. For example, a contact-running type may be applied.

[0114] The suspension 154 is connected to one end of an arm 155 (for example, an actuator arm). The arm 155 has, for example, a bobbin section. The bobbin section holds a drive coil. A voice coil motor 156 is provided at the other end of the arm 155. The voice coil motor 156 is a type of linear motor. The voice coil motor 156 includes, for example, a drive coil and a magnetic circuit. The drive coil is wound around the bobbin section of the arm 155. The magnetic circuit includes a permanent magnet and an opposing yoke. The drive coil is provided between the permanent magnet and the opposing yoke. The suspension 154 has one end and the other end. A magnetic head is provided at one end of the suspension 154. The arm 155 is connected to the other end of the suspension 154.

[0115] The arm 155 is held by ball bearings. Ball bearings are provided at two locations, above and below the bearing portion 157. The arm 155 can rotate and slide by a voice coil motor 156. The magnetic head can move to any position on the recording medium disk 180.

[0116] Figure 19(a) illustrates a part of the configuration of a magnetic recording device and is an enlarged perspective view of the head stack assembly 160. Figure 19(b) is a perspective view illustrating a magnetic head assembly (head gimbal assembly: HGA) 158, which is part of the head stack assembly 160.

[0117] As shown in Figure 19(a), the head stack assembly 160 includes a bearing section 157, a head gimbal assembly 158, and a support frame 161. The head gimbal assembly 158 extends from the bearing section 157. The support frame 161 extends from the bearing section 157. The direction in which the support frame 161 extends is opposite to the direction in which the head gimbal assembly 158 extends. The support frame 161 supports the coil 162 of the voice coil motor 156.

[0118] As shown in Figure 19(b), the head gimbal assembly 158 includes an arm 155 extending from a bearing portion 157 and a suspension 154 extending from the arm 155.

[0119] A head slider 159 is provided at the tip of the suspension 154. A magnetic head according to the embodiment is provided on the head slider 159.

[0120] The magnetic head assembly (head gimbal assembly) 158 according to the embodiment includes a magnetic head according to the embodiment, a head slider 159 on which the magnetic head is provided, a suspension 154, and an arm 155. The head slider 159 is provided at one end of the suspension 154. The arm 155 is connected to the other end of the suspension 154.

[0121] The suspension 154 may have, for example, lead wires (not shown) for recording and reproducing signals. The suspension 154 may also have, for example, lead wires (not shown) for heaters for adjusting the amount of levitation. The suspension 154 may also have, for example, lead wires (not shown) for an oscillator or the like. These lead wires are electrically connected to a plurality of electrodes provided on the magnetic head.

[0122] In the magnetic recording device 150, a signal processing unit 190 is provided. The signal processing unit 190 records and reproduces signals on a magnetic recording medium using a magnetic head. The input and output lines of the signal processing unit 190 are connected, for example, to the electrode pads of the head gimbal assembly 158 and are electrically connected to the magnetic head.

[0123] The magnetic recording apparatus 150 according to the embodiment includes a magnetic recording medium, a magnetic head according to the embodiment, a movable part, a position control unit, and a signal processing unit. The movable part allows the magnetic recording medium and the magnetic head to move relative to each other while separated or in contact. The position control unit aligns the magnetic head to a predetermined recording position on the magnetic recording medium. The signal processing unit records and reproduces signals on the magnetic recording medium using the magnetic head.

[0124] For example, a recording medium disk 180 is used as the magnetic recording medium. The movable part includes, for example, a head slider 159. The position control unit includes, for example, a head gimbal assembly 158.

[0125] The embodiment may include the following configuration (e.g., proposed technical details). (Composition 1) The first magnetic pole and, The second magnetic pole and, A magnetic element provided between the first magnetic pole and the second magnetic pole, A first terminal electrically connected to the first magnetic pole, A second terminal electrically connected to the second magnetic pole, Coil and, A magnetic head including, A control unit electrically connected to the first terminal, the second terminal and the coil, Equipped with, One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit is capable of recording operations, The control unit, in the recording operation, supplies a recording current to the coil while applying an element voltage between the first terminal and the second terminal that is between a first voltage and a second voltage. When the element voltage, the first voltage, and the second voltage are applied, the second potential of the second magnetic pole is lower than the first potential of the first magnetic pole. When the recording current is supplied to the coil and the positive applied voltage applied between the first terminal and the second terminal is changed, the differential resistance of the magnetic element reaches a first peak when the applied voltage is the first voltage. When the aforementioned positive applied voltage is applied, the second potential is lower than the first potential. When the recording current is supplied to the coil and a first applied voltage is applied between the first terminal and the second terminal, a first signal is generated between the first terminal and the second terminal. The ratio of the absolute value of the difference between the first intensity of the first signal when the first applied voltage is a positive first value and the second intensity of the first signal when the first applied voltage is a negative second value, to the normalized rate of change, is 1 or less at the second voltage. The absolute value of the second value is the same as the first value. When the first applied voltage is positive, the second potential is lower than the first potential. When the first applied voltage is negative, the second potential is higher than the first potential. A magnetic recording device in which the normalized rate of change is the product of the absolute value of the rate of change of the second intensity with respect to the first applied voltage when the first applied voltage is negative, and the first voltage.

[0126] (Configuration 2) The magnetic recording apparatus according to configuration 1, wherein the differential resistor does not have any peaks other than the first peak between the first voltage and the second voltage.

[0127] (Composition 3) The magnetic recording apparatus according to configuration 1 or 2, wherein the absolute value of the difference increases monotonically with increasing absolute value of the first applied voltage.

[0128] (Composition 4) A magnetic recording device according to any one of configurations 1 to 3, wherein the frequency of the first signal is 10 Hz or more and 3 GHz or less.

[0129] (Composition 5) The aforementioned magnetic circuit is A first magnetic layer provided between the first magnetic pole and the second magnetic pole, A second magnetic layer is provided between the first magnetic layer and the second magnetic pole, A third magnetic layer is provided between the second magnetic layer and the second magnetic pole, A fourth magnetic layer is provided between the third magnetic layer and the second magnetic pole, Includes, The first thickness of the first magnetic layer along the first direction from the first magnetic pole to the second magnetic pole is greater than the second thickness of the second magnetic layer along the first direction, and greater than the fourth thickness of the fourth magnetic layer along the first direction. A magnetic recording apparatus according to any one of configurations 1 to 4, wherein the third thickness of the third magnetic layer along the first direction is greater than the second thickness and greater than the fourth thickness.

[0130] (Composition 6) The aforementioned magnetic circuit is A first non-magnetic layer is provided between the first magnetic pole and the first magnetic layer, A second non-magnetic layer is provided between the first magnetic layer and the second magnetic layer, A third non-magnetic layer is provided between the second magnetic layer and the third magnetic layer, A fourth non-magnetic layer is provided between the third magnetic layer and the fourth magnetic layer, A fifth non-magnetic layer is provided between the fourth magnetic layer and the second magnetic pole, Includes, The first non-magnetic layer comprises at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The second nonmagnetic layer comprises at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The third non-magnetic layer comprises at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The fourth nonmagnetic layer comprises at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The magnetic recording apparatus according to configuration 5, wherein the fifth non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0131] (Composition 7) When the first applied voltage is positive, the intensity of the first frequency component of the first signal changes in accordance with the change in the first applied voltage. The first frequency is between 10 Hz and 3 GHz. The first applied voltage includes a first voltage range between the first voltage and the second voltage, and a second voltage range above the second voltage. The rate of change of the intensity with respect to the change in the first applied voltage is a first rate of change in the first voltage range and a second rate of change in the second voltage range. The magnetic recording device according to any one of configurations 1 to 6, wherein the second rate of change is higher than the first rate of change.

[0132] (Composition 8) The first applied voltage further includes a third voltage range less than the first voltage, The aforementioned rate of change is the third rate of change in the third voltage range, The magnetic recording apparatus according to configuration 7, wherein the third rate of change is lower than the first rate of change.

[0133] (Composition 9) In the recording operation described above, a signal of a second frequency is generated from the magnetic element. The magnetic recording device according to any one of configurations 1 to 8, wherein the second frequency is 10 GHz or more and 50 GHz or less.

[0134] (Composition 10) The first magnetic pole and, The second magnetic pole and, A magnetic element provided between the first magnetic pole and the second magnetic pole, A first terminal electrically connected to the first magnetic pole, A second terminal electrically connected to the second magnetic pole, Coil and, A magnetic head including, A control unit electrically connected to the first terminal, the second terminal and the coil, Equipped with, One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit is capable of recording operations, The control unit, in the recording operation, supplies a recording current to the coil while applying an element voltage between the first terminal and the second terminal that is between a first voltage and a second voltage. When the element voltage, the first voltage, and the second voltage are applied, the second potential of the second magnetic pole is lower than the first potential of the first magnetic pole. When the recording current is supplied to the coil and the positive applied voltage applied between the first terminal and the second terminal is changed, the differential resistance of the magnetic element reaches a first peak when the applied voltage is the first voltage. The differential resistance reaches a second peak when the positive applied voltage is a third voltage. The third voltage is higher than the first voltage and lower than the second voltage. When the aforementioned positive applied voltage is applied, the second potential is lower than the first potential. When the recording current is supplied to the coil and a first applied voltage is applied between the first terminal and the second terminal, a first signal is generated between the first terminal and the second terminal. The ratio of the absolute value of the difference between the first intensity of the first signal when the first applied voltage is a positive first value and the second intensity of the first signal when the first applied voltage is a negative second value, to the normalized rate of change, is 5 or less at the second voltage. When the first applied voltage is positive, the second potential is lower than the first potential. When the first applied voltage is negative, the second potential is higher than the first potential. The absolute value of the second value is the same as the first value. A magnetic recording device in which the normalized rate of change is the product of the absolute value of the rate of change of the second intensity with respect to the first applied voltage when the first applied voltage is negative, and the first voltage.

[0135] (Composition 11) The magnetic recording apparatus according to configuration 10, wherein the differential resistor does not have any peaks other than the first peak and the second peak between the third voltage and the second voltage.

[0136] (Composition 12) The magnetic recording apparatus according to configuration 10 or 11, wherein the absolute value of the difference increases monotonically with increasing absolute value of the first applied voltage.

[0137] (Composition 13) The magnetic recording device according to any one of configurations 10 to 12, wherein the frequency of the first signal is 10 Hz or more and 3 GHz or less.

[0138] (Composition 14) The aforementioned magnetic circuit is A first magnetic layer provided between the first magnetic pole and the second magnetic pole, A second magnetic layer is provided between the first magnetic layer and the second magnetic pole, A third magnetic layer is provided between the second magnetic layer and the second magnetic pole, A fourth magnetic layer is provided between the third magnetic layer and the second magnetic pole, Includes, The first thickness of the first magnetic layer along the first direction from the first magnetic pole to the second magnetic pole is greater than the second thickness of the second magnetic layer along the first direction, and greater than the fourth thickness of the fourth magnetic layer along the first direction. A magnetic recording apparatus according to any one of configurations 10 to 13, wherein the third thickness of the third magnetic layer along the first direction is greater than the second thickness and greater than the fourth thickness.

[0139] (Composition 15) The aforementioned magnetic circuit is A first non-magnetic layer is provided between the first magnetic pole and the first magnetic layer, A second non-magnetic layer is provided between the first magnetic layer and the second magnetic layer, A third non-magnetic layer is provided between the second magnetic layer and the third magnetic layer, A fourth non-magnetic layer is provided between the third magnetic layer and the fourth magnetic layer, A fifth non-magnetic layer is provided between the fourth magnetic layer and the second magnetic pole, Includes, The first non-magnetic layer comprises at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The second non-magnetic layer comprises at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The third nonmagnetic layer comprises at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The fourth nonmagnetic layer comprises at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. The magnetic recording apparatus according to configuration 14, wherein the fifth non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0140] (Composition 16) When the first applied voltage is positive, the intensity of the first frequency component of the first signal changes in accordance with the change in the first applied voltage. The first frequency is between 10 Hz and 3 GHz. The first applied voltage includes a first voltage range between the first voltage and the second voltage, and a second voltage range above the second voltage. The rate of change of the intensity with respect to the change in the first applied voltage is a first rate of change in the first voltage range and a second rate of change in the second voltage range. The magnetic recording device according to any one of configurations 10 to 15, wherein the second rate of change is higher than the first rate of change.

[0141] (Composition 17) The first applied voltage further includes a third voltage range less than the first voltage, The aforementioned rate of change is the third rate of change in the third voltage range, The magnetic recording apparatus according to configuration 16, wherein the third rate of change is lower than the first rate of change.

[0142] (Composition 18) In the recording operation described above, a signal of a second frequency is generated from the magnetic element. The magnetic recording device according to any one of configurations 10 to 17, wherein the second frequency is 10 GHz or more and 50 GHz or less.

[0143] (Composition 19) The first magnetic pole and, The second magnetic pole and, A magnetic element provided between the first magnetic pole and the second magnetic pole, A first terminal electrically connected to the first magnetic pole, A second terminal electrically connected to the second magnetic pole, Coil and, A magnetic head including, A control unit electrically connected to the first terminal, the second terminal and the coil, Equipped with, One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit is capable of recording operations, The control unit, in the recording operation, supplies a recording current to the coil while applying an element voltage between the first terminal and the second terminal that is between a first voltage and a second voltage. When the element voltage, the first voltage, and the second voltage are applied, the second potential of the second magnetic pole is lower than the first potential of the first magnetic pole. When the recording current is supplied to the coil and a first applied voltage is applied between the first terminal and the second terminal, a first signal is generated between the first terminal and the second terminal. When the first applied voltage is applied, the second potential is lower than the first potential. The intensity of the first frequency component of the first signal changes in accordance with the change in the first applied voltage. The first frequency is between 10 Hz and 3 GHz. The first applied voltage includes a first voltage range between the first voltage and the second voltage, a second voltage range above the second voltage, and a third voltage range below the first voltage. The rate of change of the intensity with respect to the change in the first applied voltage is a first rate of change in the first voltage range, a second rate of change in the second voltage range, and a third rate of change in the third voltage range. The second rate of change is higher than the first rate of change. A magnetic recording device wherein the third rate of change is lower than the first rate of change.

[0144] (Composition 20) The magnetic recording device according to any one of configurations 1 to 19, wherein the element voltage is DC.

[0145] According to this embodiment, a magnetic recording device capable of improving recording density can be provided.

[0146] In this specification, "perpendicular" and "parallel" do not mean strictly perpendicular and strictly parallel, but also include variations in the manufacturing process, for example, and it is sufficient if they are substantially perpendicular and substantially parallel.

[0147] Embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, the specific configuration of each element included in the magnetic head and magnetic recording device, such as magnetic poles, magnetic elements, magnetic layers, non-magnetic layers, and control units, is included within the scope of the present invention as long as those skilled in the art can appropriately select from the known range to implement the present invention and obtain similar effects.

[0148] Combinations of two or more elements from any of the specific examples, to the extent technically feasible, are also included within the scope of the present invention, insofar as they encompass the gist of the invention.

[0149] Furthermore, all magnetic recording devices that can be implemented by those skilled in the art by appropriately modifying the design based on the magnetic recording device described above as an embodiment of the present invention also fall within the scope of the present invention, insofar as they encompass the gist of the present invention.

[0150] Furthermore, within the scope of the concept of the present invention, a person skilled in the art could conceive of various modifications and alterations, and it is understood that such modifications and alterations also fall within the scope of the present invention.

[0151] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0152] 20: Magnetic element, 20D: Element circuit, 21-24: 1st-4th magnetic layers, 21M-24M: Magnetization, 30D: Recording circuit, 30F: Media-facing surface, 30c: Coil, 30i: Insulation part, 31, 32: 1st and 2nd magnetic poles, 31M, 32M: Magnetization, 33: Shield, 41-45: 1st-5th non-magnetic layers, 60: Recording section, 70: Playback section, 71: Magnetic playback element, 72a, 72b: 1st and 2nd playback magnetic shields, 75: Control section, 80: Magnetic recording medium, 81: Magnetic recording layer, 82: Media substrate, 83: Magnetization, 85: Media movement direction, 110-113: Magnetic head, 150: Magnetic recording device, 154: Suspension, 155: Arm 156: Voice coil motor, 157: Bearing section, 158: Head gimbal assembly, 159: Head slider, 159A: Air inlet side, 159B: Air outlet side, 160: Head stack assembly, 161: Support frame, 162: Coil, 180: Recording medium disk, 180M: Spindle motor, 181: Recording medium, 190: Signal processing unit, 210: Magnetic recording device, AR: Arrow, D1: First direction, Is: Intensity, Iw: Recording current, P1: Parameter, Pd1, Pd2: First, second peak, RT1~RT3: First~third rate of change, Rd1: Differential resistance, Rv1: Electrical resistance, ST1~ST3: First~third state, Sg1: First signal, Sn1, Sp1: Intensity, Sv1, Sv2: First, second intensity, T1, T2: 1st and 2nd terminals, Tc1, Tc2: 1st and 2nd coil terminals, V1~V3: 1st to 3rd voltages, V20: element voltage, Va1: 1st applied voltage, Vap: applied voltage, Vp2: voltage, Vr1~Vr3: 1st to 3rd voltage range, Vv1, Vv2: 1st and 2nd values, W1, W2: 1st and 2nd wiring, fr0, fr21, fr23: oscillation frequency, ic: element current, je: electron current, t21~t24: 1st to 4th thickness, t41~t45… thickness

Claims

1. The first magnetic pole and, The second magnetic pole and, A magnetic element provided between the first magnetic pole and the second magnetic pole, A first terminal electrically connected to the first magnetic pole, A second terminal electrically connected to the second magnetic pole, Coil and, A magnetic head including, A control unit electrically connected to the first terminal, the second terminal and the coil, Equipped with, One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit is capable of recording operations, The control unit, in the recording operation, supplies a recording current to the coil while applying an element voltage between the first terminal and the second terminal that is between a first voltage and a second voltage. When the element voltage, the first voltage, and the second voltage are applied, the second potential of the second magnetic pole is lower than the first potential of the first magnetic pole. When the recording current is supplied to the coil and the positive applied voltage applied between the first terminal and the second terminal is changed, the differential resistance of the magnetic element reaches a first peak when the applied voltage is the first voltage. When the aforementioned positive applied voltage is applied, the second potential is lower than the first potential. When the recording current is supplied to the coil and a first applied voltage is applied between the first terminal and the second terminal, a first signal is generated between the first terminal and the second terminal. The ratio of the absolute value of the difference between the first intensity of the first signal when the first applied voltage is a positive first value and the second intensity of the first signal when the first applied voltage is a negative second value, to the normalized rate of change, is 1 or less at the second voltage. The absolute value of the second value is the same as the first value. When the first applied voltage is positive, the second potential is lower than the first potential. When the first applied voltage is negative, the second potential is higher than the first potential. A magnetic recording device in which the normalized rate of change is the product of the absolute value of the rate of change of the second intensity with respect to the first applied voltage when the first applied voltage is negative, and the first voltage.

2. The magnetic recording apparatus according to claim 1, wherein the differential resistor does not have any peaks other than the first peak between the first voltage and the second voltage.

3. The magnetic recording apparatus according to claim 1, wherein the absolute value of the difference increases monotonically with increasing absolute value of the first applied voltage.

4. The magnetic recording apparatus according to claim 1, wherein the frequency of the first signal is 10 Hz or more and 3 GHz or less.

5. The aforementioned magnetic circuit is A first magnetic layer is provided between the first magnetic pole and the second magnetic pole, A second magnetic layer is provided between the first magnetic layer and the second magnetic pole, A third magnetic layer is provided between the second magnetic layer and the second magnetic pole, A fourth magnetic layer is provided between the third magnetic layer and the second magnetic pole, Includes, The first thickness of the first magnetic layer along the first direction from the first magnetic pole to the second magnetic pole is greater than the second thickness of the second magnetic layer along the first direction, and greater than the fourth thickness of the fourth magnetic layer along the first direction. The magnetic recording apparatus according to any one of claims 1 to 4, wherein the third thickness of the third magnetic layer along the first direction is greater than the second thickness and greater than the fourth thickness.

6. The first magnetic pole and, The second magnetic pole and, A magnetic element provided between the first magnetic pole and the second magnetic pole, A first terminal electrically connected to the first magnetic pole, A second terminal electrically connected to the second magnetic pole, Coil and, A magnetic head including, A control unit electrically connected to the first terminal, the second terminal and the coil, Equipped with, One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit is capable of recording operations, The control unit, in the recording operation, supplies a recording current to the coil while applying an element voltage between the first terminal and the second terminal that is between a first voltage and a second voltage. When the element voltage, the first voltage, and the second voltage are applied, the second potential of the second magnetic pole is lower than the first potential of the first magnetic pole. When the recording current is supplied to the coil and the positive applied voltage applied between the first terminal and the second terminal is changed, the differential resistance of the magnetic element reaches a first peak when the applied voltage is the first voltage. The differential resistance reaches a second peak when the positive applied voltage is a third voltage. The third voltage is higher than the first voltage and lower than the second voltage. When the aforementioned positive applied voltage is applied, the second potential is lower than the first potential. When the recording current is supplied to the coil and a first applied voltage is applied between the first terminal and the second terminal, a first signal is generated between the first terminal and the second terminal. The ratio of the absolute value of the difference between the first intensity of the first signal when the first applied voltage is a positive first value and the second intensity of the first signal when the first applied voltage is a negative second value, to the normalized rate of change, is 5 or less at the second voltage. When the first applied voltage is positive, the second potential is lower than the first potential. When the first applied voltage is negative, the second potential is higher than the first potential. The absolute value of the second value is the same as the first value. A magnetic recording device in which the normalized rate of change is the product of the absolute value of the rate of change of the second intensity with respect to the first applied voltage when the first applied voltage is negative, and the first voltage.

7. The magnetic recording apparatus according to claim 6, wherein the differential resistor does not have any peaks other than the first peak and the second peak between the third voltage and the second voltage.

8. The magnetic recording apparatus according to claim 6, wherein the absolute value of the difference increases monotonically with increasing absolute value of the first applied voltage.

9. The aforementioned magnetic circuit is A first magnetic layer is provided between the first magnetic pole and the second magnetic pole, A second magnetic layer is provided between the first magnetic layer and the second magnetic pole, A third magnetic layer is provided between the second magnetic layer and the second magnetic pole, A fourth magnetic layer is provided between the third magnetic layer and the second magnetic pole, Includes, The first thickness of the first magnetic layer along the first direction from the first magnetic pole to the second magnetic pole is greater than the second thickness of the second magnetic layer along the first direction, and greater than the fourth thickness of the fourth magnetic layer along the first direction. The magnetic recording apparatus according to any one of claims 6 to 8, wherein the third thickness of the third magnetic layer along the first direction is greater than the second thickness and greater than the fourth thickness.

10. The first magnetic pole and, The second magnetic pole and, A magnetic element provided between the first magnetic pole and the second magnetic pole, A first terminal electrically connected to the first magnetic pole, A second terminal electrically connected to the second magnetic pole, Coil and, A magnetic head including, A control unit electrically connected to the first terminal, the second terminal and the coil, Equipped with, One end of the magnetic element is electrically connected to the first magnetic pole. The other end of the magnetic element is electrically connected to the second magnetic pole. The control unit is capable of recording operations, The control unit, in the recording operation, supplies a recording current to the coil while applying an element voltage between the first terminal and the second terminal that is between a first voltage and a second voltage. When the element voltage, the first voltage, and the second voltage are applied, the second potential of the second magnetic pole is lower than the first potential of the first magnetic pole. When the recording current is supplied to the coil and a first applied voltage is applied between the first terminal and the second terminal, a first signal is generated between the first terminal and the second terminal. When the first applied voltage is applied, the second potential is lower than the first potential. The intensity of the first frequency component of the first signal changes in accordance with the change in the first applied voltage. The first frequency is between 10 Hz and 3 GHz. The first applied voltage includes a first voltage range between the first voltage and the second voltage, a second voltage range above the second voltage, and a third voltage range below the first voltage. The rate of change of the intensity with respect to the change in the first applied voltage is a first rate of change in the first voltage range, a second rate of change in the second voltage range, and a third rate of change in the third voltage range. The second rate of change is higher than the first rate of change. A magnetic recording device wherein the third rate of change is lower than the first rate of change.

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