Magnetic recorder

Abstract

To provide a magnetic recorder capable of improving recording density.SOLUTION: According to an embodiment, a magnetic recorder includes a magnetic head and a magnetic recording medium. The magnetic head includes: a first magnetic pole; a second magnetic pole; and a magnetic element provided between the first magnetic pole and the second magnetic pole. The magnetic element includes a first magnetic layer and a second magnetic layer. The magnetic element includes a middle point between the first magnetic layer and the second magnetic layer in a first direction from the first magnetic pole to the second magnetic pole. A first ratio r1 and a second ratio r2 satisfy that r2 is equal to or more than -0.26×r1+0.60 and equal to or less than 0.26×r2+0.70. The first ratio r1 is a ratio of a second distance L2 between the first magnetic pole and the middle point with respect to a first distance L1 between the first magnetic pole and the second magnetic pole. The second ratio r2 is a ratio of a dynamic coercive force Hc0 of the magnetic recording medium with respect to an average anisotropic magnetic field Hk.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present embodiment relates to a magnetic recording device. [Background technology]

[0002] 2. Description of the Related Art Information is recorded on a magnetic recording medium such as a hard disk drive (HDD) by using a magnetic head. In magnetic recording devices, it is desirable to improve the recording density. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-129730 A Summary of the Invention [Problem to be solved by the invention]

[0004] An embodiment of the present invention provides a magnetic recording device capable of improving recording density. [Means for solving the problem]

[0005] According to an embodiment, a magnetic recording device includes a magnetic head and a magnetic recording medium. The magnetic head includes a first magnetic pole, a second magnetic pole, and a magnetic element provided between the first magnetic pole and the second magnetic pole. The magnetic element includes a first magnetic layer and a second magnetic layer provided between the first magnetic layer and the second magnetic pole. The magnetic element includes a midpoint between the first magnetic layer and the second magnetic layer in a first direction from the first magnetic pole to the second magnetic pole. A first ratio r1 and a second ratio r2 satisfy -0.26 x r1 + 0.60 ≦ r2 ≦ -0.26 x r2 + 0.70. The first ratio r1 is a ratio of a second distance L2 between the first magnetic pole and the midpoint in the first direction to a first distance L1 between the first magnetic pole and the second magnetic pole in the first direction. The second ratio r2 is the ratio of the dynamic coercivity Hc0 of the magnetic recording medium to the average anisotropy magnetic field Hk of the magnetic recording medium. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating the magnetic recording device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view illustrating a part of the magnetic recording device according to the first embodiment. [Diagram 3] FIG. 3 is a graph illustrating the characteristics of a magnetic recording device. [Figure 4] FIG. 4 is a graph illustrating the characteristics of a magnetic recording device. [Diagram 5] FIG. 5 is a graph illustrating the characteristics of a magnetic recording device. [Figure 6] FIG. 6 is a schematic cross-sectional view illustrating a part of the magnetic recording device according to the first embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view illustrating a part of the magnetic recording device according to the first embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view illustrating a portion of the magnetic recording device according to the first embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view illustrating a part of the magnetic recording device according to the first embodiment. [Figure 10] FIG. 10 is a schematic perspective view illustrating the magnetic recording device according to the embodiment. [Figure 11] FIG. 11 is a schematic perspective view illustrating a portion of the magnetic recording device according to the embodiment. [Figure 12] FIG. 12 is a schematic perspective view illustrating the magnetic recording device according to the embodiment. [Figure 13] 13A and 13B are schematic perspective views illustrating a part of the magnetic recording device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] (First embodiment) FIG. 1 is a schematic cross-sectional view illustrating the magnetic recording device according to the first embodiment. 1, a magnetic recording device 210 according to the embodiment includes a magnetic head 110 and a magnetic recording medium 80. The magnetic recording device 210 may include a control unit 75. 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 section 60. As described below, the magnetic head 110 may also include a reproducing section. The recording section 60 includes a first magnetic pole 31, a second magnetic pole 32, and a magnetic element 20. The magnetic head 110 may include a coil 30c. The magnetic element 20 is provided between a first magnetic pole 31 and a 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 main magnetic pole. The second magnetic pole 32 is, for example, a trailing shield. The first magnetic pole 31 may be the trailing shield and the second magnetic pole 32 may be the main 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. A direction perpendicular to the Z-axis direction and the X-axis direction is defined as the Y-axis direction. The Z-axis direction corresponds to the height direction, for example. The X-axis direction corresponds to the down-track direction, for example. The Y-axis direction corresponds to the cross-track direction, for example. The magnetic recording medium 80 and the magnetic head 110 move relatively along the down-track direction. A recording magnetic field generated by 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 to a direction according to the recording magnetic field. As a result, 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 a first direction D1. The first direction D1 may be substantially along the X-axis direction. In the embodiment, the first direction D1 may be inclined with respect to the X-axis direction. The angle of inclination may be, for example, not less than 0 degrees and not more than 40 degrees.

[0012] In this example, a portion 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 portion 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. The recording current Iw is supplied to the coil 30c via these coil terminals. A recording magnetic field corresponding to the recording current Iw is applied to the magnetic recording medium 80 from the first magnetic pole 31.

[0014] 1, the first magnetic pole 31 includes a medium facing surface 30F. The medium facing surface 30F is, for example, an air bearing surface (ABS). The medium facing surface 30F faces, for example, a magnetic recording medium 80. The medium facing surface 30F is along, for example, the XY plane.

[0015] As shown in FIG. 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. A first terminal T1 and a second terminal T2 are provided on the magnetic head 110. 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. For example, an element current ic is supplied to the magnetic element 20 from the element circuit 20D.

[0016] 1, the element current ic is oriented from the first magnetic pole 31 to the second magnetic pole 32. As shown in FIG 1, the electron flow je accompanying the element current ic is oriented from the second magnetic pole 32 to the first magnetic pole 31. The element current ic includes a DC component. The element current ic may be, for example, a direct current.

[0017] For example, an element current ic equal to or greater than a threshold flows through the magnetic element 20, causing oscillation in a magnetic layer included in the magnetic element 20. The magnetic element 20 functions as, for example, a spin-torque oscillator (STO). In association 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 recording on the magnetic recording medium 80. For example, microwave assisted magnetic recording (MAMR) is possible. For example, the electrical resistance of the magnetic element 20 oscillates in response to the alternating magnetic field from the magnetic element 20. The oscillation of the electrical resistance corresponds to the alternating magnetic field.

[0018] Oscillation of magnetization occurs in the first magnetic layer 21 and the second magnetic layer 22. These magnetic layers are, for example, oscillation layers.

[0019] The recording circuit 30D and the element circuit 20D are included in a 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 supply an element current ic to the magnetic element 20.

[0020] For example, the control unit 75 (element circuit 20D) applies an element voltage V20 corresponding to the element current i c between the first terminal T1 and the second terminal T2. In practice, the element current i c may be controlled by controlling the element voltage V20. In a recording operation, the control unit 75 supplies a recording current Iw to the coil 30c while applying the element voltage V20 between the first terminal T1 and the second terminal T2.

[0021] An example of the magnetic head 110 will now be described. FIG. 2 is a schematic cross-sectional view illustrating a part of the magnetic recording device according to the first embodiment. 2, the magnetic element 20 includes a first magnetic layer 21 and a second magnetic layer 22. The second magnetic layer 22 is provided between the first magnetic layer 21 and the second magnetic pole 32. As described below, the magnetic element 20 may further include other magnetic layers.

[0022] The magnetic element 20 includes a midpoint P1. The midpoint P1 is the midpoint between the first magnetic layer 21 and the second magnetic layer 22 in a first direction D1 from the first magnetic pole 31 to the second magnetic pole 32.

[0023] The distance between the first magnetic pole 31 and the second magnetic pole 32 in the first direction D1 is defined as a first distance L1. The distance between the first magnetic pole 31 and the midpoint P1 in the first direction D1 is defined as a second distance L2. The first ratio r1 is the ratio (L2 / L1) of the second distance L2 to the first distance L1. The first ratio r1 is greater than 0 and less than 1.

[0024] The second ratio r2 is the ratio (Hc0 / Hk) of the dynamic coercivity Hc0 of the magnetic recording medium 80 to the average anisotropy magnetic field Hk of the magnetic recording medium 80. As described below, the magnetic recording medium 80 includes a magnetic recording layer 81. The dynamic coercivity Hc0 of the magnetic recording medium 80 may be the dynamic coercivity Hc0 of the magnetic recording layer. The average anisotropy magnetic field Hk of the magnetic recording medium 80 may be the average anisotropy magnetic field Hk of the magnetic recording layer. The dynamic coercivity Hc0 is a coercivity evaluated over a time period of, for example, 1 ns or more and 10 ns or less. The time period of, for example, 1 ns or more and 10 ns or less corresponds to the time from the start to the end of magnetization reversal in the magnetic recording device 210.

[0025] In an embodiment, the first ratio r1 and the second ratio r2 are: -0.26×r1+0.60 ≦ r2 ≦ -0.26×r2+0.70 …(1) Meet the following.

[0026] When the above first formula is satisfied, for example, a high SNR can be obtained. For example, recording with a high SNR can be performed at a high recording density. Even at a high recording density, a low error rate can be maintained. According to the embodiment, a magnetic recording device capable of improving the recording density can be provided.

[0027] An example of a simulation result for the characteristics of a magnetic recording device will be described below. In the following example, the first distance L1 is fixed and the second distance L2 is changed. In the following example, the first distance L1 is 27 nm. The magnetized volume of the first magnetic layer 21 is 16 nmT. The magnetized volume of the second magnetic layer 22 is 16 nmT. The average anisotropic magnetic field Hk is kept constant, and the dynamic coercivity Hc0 is changed. The average anisotropic magnetic field Hk is 19400 kOe.

[0028] 3 and 4 are graphs illustrating the characteristics of the magnetic recording device. In these figures, the horizontal axis is the second ratio r2, and the vertical axis is the SNR. The SNR is calculated by multiplying the output S of the reproduced signal by 20log 10 The first ratio r1 is defined as the signal-to-noise ratio (S / N). In Fig. 3, the first ratio r1 is 0.5. In Fig. 4, the first ratio r1 is 0.7.

[0029] As shown in Fig. 3, when the first ratio r1 is 0.5, the SNR is high when the second ratio r2 is about 0.54. When the second ratio r2 is less than 0.54, the SNR increases with the increase in the second ratio r2. When the second ratio r2 is higher than 0.54, the SNR decreases with the increase in the second ratio r2.

[0030] As shown in Fig. 4, when the first ratio r1 is 0.7, the SNR is high when the second ratio r2 is about 0.44. When the second ratio r2 is less than 0.44, the SNR increases with the increase in the second ratio r2. When the second ratio r2 is higher than 0.44, the SNR decreases with the increase in the second ratio r2.

[0031] In this way, the second ratio r2 at which a high SNR is obtained varies depending on the value of the first ratio r1. When the SNR is 9.0 or higher, recording at a practically high density is possible.

[0032] FIG. 5 is a graph illustrating the characteristics of a magnetic recording device. In FIG. 5, the horizontal axis is the first ratio r1, and the vertical axis is the second ratio r2. In FIG. 5, black circles indicate that an SNR of 0.75 or more is obtained, and white circles indicate that the SNR is less than 0.75. As shown in FIG. 5, the condition (black circle) for obtaining an SNR of 9.0 or more is: r2=-0.2612×r1+0.6493 …(2) It is expressed as:

[0033] When the second formula is satisfied, a high SNR is obtained. When an error of 0.5 is considered in the relationship of the second formula, the relationship of the first formula above is obtained. In practice, when the first formula is satisfied, a high SNR is obtained.

[0034] For example, the recording magnetic field generated from the first magnetic pole 31 is applied to the magnetic recording medium 80 and acts on the magnetization of the magnetic recording medium 80. Meanwhile, the alternating magnetic field generated from the magnetic element 20 is applied to the magnetic recording medium 80. Considering the dynamic coercive force Hc0 of the magnetic recording medium 80, it is considered that there is an appropriate relationship between the position where the recording magnetic field substantially affects the magnetization of the magnetic recording medium 80 and the position of the midpoint P1 of the two oscillation layers. When the above first formula is satisfied, it is considered that the alternating magnetic field generated from the magnetic element 20 is appropriately applied to the position where the recording magnetic field substantially affects the magnetization of the magnetic recording medium 80. As a result, it is considered that a high SNR can be obtained when the first formula is satisfied.

[0035] In the embodiment, the first ratio r1 is preferably, for example, not less than 0.35 and not more than 0.7, in which case a stable alternating magnetic field can be easily obtained with high efficiency.

[0036] In the embodiment, the second ratio r2 is preferably, for example, not less than 0.45 and not more than 0.56. In this case, it is easy to obtain a magnetic recording medium 80 with stable characteristics. It is easy to obtain stable characteristics.

[0037] In this embodiment, the average anisotropic magnetic field Hk is preferably 17,300 Oe or more and 21,200 Oe or less. The dynamic coercivity Hc0 is preferably 7,500 Oe or more and 11,000 Oe or less. A magnetic recording medium 80 with stable characteristics can be obtained.

[0038] In the embodiment, the first distance L1 is preferably, for example, not less than 15 nm and not more than 50 nm, so that a high-intensity alternating magnetic field can be stably obtained.

[0039] In the embodiment, the product of the first saturation magnetization of the first magnetic layer 21 and the thickness of the first magnetic layer 21 in the first direction D1 (first magnetic layer thickness t1 described later) is preferably 9 nmT or more and 19 nmT or less. The product of the second saturation magnetization of the second magnetic layer 22 and the thickness of the second magnetic layer 22 in the first direction D1 (second magnetic layer thickness t2 described later) is preferably 9 nmT or more and 19 nmT or less. Stable oscillation is easily obtained. A stable alternating magnetic field is obtained.

[0040] 6 and 7 are schematic cross-sectional views illustrating a part of the magnetic recording device according to the first embodiment. 6, in a magnetic head 111 included in a magnetic recording device 210 according to the embodiment, the magnetic element 20 includes a third magnetic layer 23 and a fourth magnetic layer 24. Except for this, the configuration of the magnetic head 111 may be similar to the configuration of the magnetic head 110.

[0041] 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. As already described, 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 first magnetic pole 31 and the first magnetic layer 21. The fourth magnetic layer 24 is provided between the first magnetic layer 21 and the second magnetic layer 22.

[0042] 7, the thickness of the first magnetic layer 21 along the first direction D1 is defined as a first magnetic layer thickness t1. The thickness of the second magnetic layer 22 along the first direction D1 is defined as a second magnetic layer thickness t2. The thickness of the third magnetic layer 23 along the first direction D1 is defined as a third magnetic layer thickness t3. The thickness of the fourth magnetic layer 24 along the first direction D1 is defined as a fourth magnetic layer thickness t4.

[0043] In the embodiment, the first magnetic layer thickness t1 is thicker than the third magnetic layer thickness t3. The second magnetic layer thickness t2 is thicker than the fourth magnetic layer thickness t4. The first magnetic layer thickness t1 is thicker than the fourth magnetic layer thickness t4. The second magnetic layer thickness t2 is thicker than the third magnetic layer thickness t3.

[0044] For example, the first magnetic layer 21 and the second magnetic layer 22 function as an oscillation layer, and the third magnetic layer 23 and the fourth magnetic layer 24 function as a spin injection layer.

[0045] The magnetic element 20 may include, for example, a first nonmagnetic layer 41, a second nonmagnetic layer 42, a third nonmagnetic layer 43, a fourth nonmagnetic layer 44, and a fifth nonmagnetic layer 45. The first nonmagnetic layer 41 is provided between the first magnetic layer 21 and the fourth magnetic layer 24. The second nonmagnetic layer 42 is provided between the fourth magnetic layer 24 and the second magnetic layer 22. The third nonmagnetic layer 43 is provided between the first magnetic pole 31 and the third magnetic layer 23. The fourth nonmagnetic layer 44 is provided between the third magnetic layer 23 and the first magnetic layer 21. The fifth nonmagnetic layer 45 is provided between the second magnetic layer 22 and the second magnetic pole 32.

[0046] In the magnetic head 111, the first non-magnetic layer 41 contacts the first magnetic layer 21 and the fourth magnetic layer 24. The second non-magnetic layer 42 contacts the fourth magnetic layer 24 and the second magnetic layer 22. The third non-magnetic layer 43 contacts the first magnetic pole 31 and the third magnetic layer 23. The fourth non-magnetic layer 44 contacts the third magnetic layer 23 and the first magnetic layer 21. The fifth non-magnetic layer 45 contacts the second magnetic layer 22 and the second magnetic pole 32.

[0047] In the magnetic head 111 as well, the magnetic element 20 includes the midpoint P1 (see FIG. 6). The relationship of the first formula is also satisfied in the magnetic head 111. This allows a high SNR to be obtained.

[0048] In the magnetic head 111, the first magnetic layer thickness t1 is preferably, for example, 5 nm or more and 15 nm or less. The second magnetic layer thickness t2 is preferably, for example, 5 nm or more and 15 nm or less. The third magnetic layer thickness t3 is preferably, for example, 1 nm or more and 5 nm or less. The fourth magnetic layer thickness t4 is preferably, for example, 1 nm or more and 5 nm or less. A stable alternating magnetic field is easily obtained.

[0049] In the magnetic head 111, the product of the first saturation magnetization and the first magnetic layer thickness t1 of the first magnetic layer 21 is preferably 9 nmT or more and 19 nmT or less. The product of the second saturation magnetization and the second magnetic layer thickness t2 of the second magnetic layer 22 is preferably 9 nmT or more and 19 nmT or less. The product of the third saturation magnetization and the third magnetic layer thickness t3 of the third magnetic layer 23 is preferably 2 nmT or more and 10 nmT or less. The product of the fourth saturation magnetization and the fourth magnetic layer thickness t4 of the fourth magnetic layer 24 is preferably 2 nmT or more and 10 nmT or less. For example, a stable alternating magnetic field can be obtained with high efficiency.

[0050] 2, a nonmagnetic layer corresponding to at least one of the first nonmagnetic layer 41 and the second nonmagnetic layer 42 may be provided between the first magnetic layer 21 and the second magnetic layer 22. In the magnetic head 110, a nonmagnetic layer corresponding to at least one of the third nonmagnetic layer 43 and the fourth nonmagnetic layer 44 may be provided between the first magnetic pole 31 and the second magnetic layer 22. In the magnetic head 110, a nonmagnetic layer corresponding to the fifth nonmagnetic layer 45 may be provided between the second magnetic layer 22 and the second magnetic pole 32.

[0051] In the magnetic head 111, The first nonmagnetic layer 41 contains at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The second nonmagnetic layer 42 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The third nonmagnetic layer 43 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The fourth nonmagnetic layer 44 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The fifth nonmagnetic layer 45 contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. This makes it easy to obtain a stable alternating magnetic field.

[0052] As shown in FIG. 7, the first nonmagnetic layer 41 has a first nonmagnetic layer thickness t41 along the first direction D1. The first nonmagnetic layer thickness t41 is preferably, for example, 0.5 nm or more and 6 nm or less. The second nonmagnetic layer thickness t42 is preferably, for example, 0.5 nm or more and 6 nm or less. The third nonmagnetic layer thickness t43 is preferably, for example, 0.5 nm or more and 6 nm or less. The fourth nonmagnetic layer thickness t44 is preferably, for example, 0.5 nm or more and 6 nm or less. The fifth nonmagnetic layer thickness t45 is preferably, for example, 0.5 nm or more and 6 nm or less. A stable alternating magnetic field is easily obtained.

[0053] As shown in Fig. 6, in the magnetic head 111, the first direction D1 is inclined with respect to the X-axis direction. As shown in Fig. 6, the magnetic head 110 includes a medium facing surface 30F. The angle between the first direction D1 and the medium facing surface 30F may be equal to or greater than 0 degrees and equal to or less than 40 degrees.

[0054] FIG. 8 is a schematic cross-sectional view illustrating a portion of the magnetic recording device according to the first embodiment. 8, in a magnetic head 112 included in a magnetic recording device 210 according to the embodiment, the material of the nonmagnetic layer included in the magnetic element 20 is different from the material of the nonmagnetic layer included in the magnetic head 111. Except for this, the configuration of the magnetic head 112 may be similar to the configuration of the magnetic head 111.

[0055] In the magnetic head 112, The first nonmagnetic layer 41 contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The second nonmagnetic layer 42 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The third nonmagnetic layer 43 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The fourth nonmagnetic layer 44 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The fifth non-magnetic layer 45 contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. This makes it easy to obtain a stable alternating magnetic field. The magnetic head 112 also satisfies the relationship of the first formula above. A high SNR can be obtained.

[0056] FIG. 9 is a schematic cross-sectional view illustrating a part of the magnetic recording device according to the first embodiment. 9, in a magnetic head 113 included in a magnetic recording device 210 according to the embodiment, the material of the nonmagnetic layer included in the magnetic element 20 is different from the material of the nonmagnetic layer included in the magnetic head 111. Except for this, the configuration of the magnetic head 113 may be similar to the configuration of the magnetic head 111.

[0057] In the magnetic head 113, The first nonmagnetic layer 41 contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The second nonmagnetic layer 42 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The third nonmagnetic layer 43 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. The fourth nonmagnetic layer 44 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The fifth non-magnetic layer 45 contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. This makes it easy to obtain a stable alternating magnetic field. The magnetic head 113 also satisfies the relationship of the first formula above. A high SNR can be obtained.

[0058] Other configuration examples of the magnetic recording device according to the embodiment will be described below.

[0059] FIG. 10 is a schematic perspective view illustrating the magnetic recording device according to the embodiment. 10, a magnetic head according to an embodiment (e.g., 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 reproducing unit 70. The recording unit 60 of the magnetic head 110 records information on the magnetic recording medium 80. The reproducing unit 70 reproduces the information recorded on the magnetic recording medium 80.

[0060] The magnetic recording medium 80 includes, for example, a medium substrate 82 and a magnetic recording layer 81 provided on the medium substrate 82. The magnetization 83 of the magnetic recording layer 81 is controlled by the recording unit 60.

[0061] In the embodiment, the thickness of the magnetic recording layer 81 may be, for example, 5 nm or more and 50 nm or less. It is easy to obtain a magnetic recording layer 81 with stable characteristics. The magnetic recording layer 81 may be, for example, a perpendicular magnetization film.

[0062] The reproducing unit 70 includes, for example, a first reproducing magnetic shield 72a, a second reproducing magnetic shield 72b, and a magnetic reproducing element 71. The magnetic reproducing element 71 is provided between the first reproducing magnetic shield 72a and the second reproducing magnetic shield 72b. The magnetic reproducing element 71 can output a signal corresponding to the magnetization 83 of the magnetic recording layer 81.

[0063] 10, the magnetic recording medium 80 moves relative to the magnetic head 110 in a medium movement direction 85. The magnetic head 110 controls information corresponding to the magnetization 83 of the magnetic recording layer 81 at an arbitrary position. The magnetic head 110 reproduces information corresponding to the magnetization 83 of the magnetic recording layer 81 at an arbitrary position.

[0064] FIG. 11 is a schematic perspective view illustrating a portion of the magnetic recording device according to the embodiment. FIG. 11 illustrates a head slider. The magnetic head 110 is provided on a head slider 159. The head slider 159 includes, for example, Al2O3 / TiC, etc. The head slider 159 moves relative to the magnetic recording medium while floating above or in contact with the magnetic recording medium.

[0065] The head slider 159 has, for example, an air inflow side 159A and an air outflow side 159B. The magnetic head 110 is disposed on a side surface of the air outflow side 159B of the head slider 159. This allows the magnetic head 110 to move relative to the magnetic recording medium while floating above or in contact with the magnetic recording medium.

[0066] FIG. 12 is a schematic perspective view illustrating the magnetic recording device according to the embodiment. 13A and 13B are schematic perspective views illustrating a part of the magnetic recording device according to the embodiment. As shown in FIG. 12, a rotary actuator is used in the magnetic recording device 150 according to the embodiment. The recording medium disk 180 is mounted on a spindle motor 180M. The recording medium disk 180 is rotated in the direction of the arrow AR by the spindle motor 180M. The spindle motor 180M responds to a control signal from a drive control unit. The magnetic recording device 150 according to the embodiment may include a plurality of recording medium disks 180. The magnetic recording device 150 may include a recording medium 181. The recording medium 181 is, for example, an SSD (Solid State Drive). For the recording medium 181, for example, a non-volatile memory such as a flash memory is used. For example, the magnetic recording device 150 may be a hybrid HDD (Hard Disk Drive).

[0067] The head slider 159 records and reproduces information to be recorded on the recording medium disk 180. The head slider 159 is provided at the tip of the thin-film suspension 154. Near the tip of the head slider 159, a magnetic head according to the embodiment is provided.

[0068] When the recording medium disk 180 rotates, the pressing pressure by the suspension 154 and the pressure generated at the medium facing surface (ABS) of the head slider 159 are balanced. The distance between the medium facing surface of the head slider 159 and the surface of the recording medium disk 180 is a predetermined flying height. In an embodiment, the head slider 159 may be in contact with the recording medium disk 180. For example, a contact running type may be applied.

[0069] The suspension 154 is connected to one end of an arm 155 (e.g., an actuator arm). The arm 155 has, for example, a bobbin portion. The bobbin portion 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 portion 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. The magnetic head is provided at one end of the suspension 154. The arm 155 is connected to the other end of the suspension 154.

[0070] Arm 155 is held by a ball bearing. The ball bearings are provided at two locations, above and below bearing portion 157. Arm 155 can rotate and slide by voice coil motor 156. The magnetic head can be moved to any position on recording medium disk 180.

[0071] FIG. 13A illustrates a partial configuration of the magnetic recording device, and is an enlarged perspective view of a head stack assembly 160. FIG. FIG. 13B is a perspective view illustrating a magnetic head assembly (head gimbal assembly: HGA) 158 which is a part of the head stack assembly 160.

[0072] 13(a), the head stack assembly 160 includes a bearing portion 157, a head gimbal assembly 158, and a support frame 161. The head gimbal assembly 158 extends from the bearing portion 157. The support frame 161 extends from the bearing portion 157. The extension direction of the support frame 161 is opposite to the extension direction of the head gimbal assembly 158. The support frame 161 supports a coil 162 of the voice coil motor 156.

[0073] As shown in FIG. 13( b ), the head gimbal assembly 158 has an arm 155 extending from a bearing portion 157 , and a suspension 154 extending from the arm 155 .

[0074] A head slider 159 is provided at the tip of the suspension 154. The head slider 159 is provided with a magnetic head according to the embodiment.

[0075] A magnetic head assembly (head gimbal assembly) 158 according to the embodiment includes a magnetic head according to the embodiment, a head slider 159 provided with the magnetic head, 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.

[0076] The suspension 154 has, for example, lead wires (not shown) for recording and reproducing signals. The suspension 154 may have, for example, lead wires (not shown) for a heater for adjusting the flying height. The suspension 154 may have, for example, lead wires (not shown) for an oscillation element or the like. These lead wires are electrically connected to a plurality of electrodes provided on the magnetic head.

[0077] A signal processing unit 190 is provided in the magnetic recording device 150. The signal processing unit 190 uses a magnetic head to record and reproduce signals on a magnetic recording medium. The input / output lines of the signal processing unit 190 are connected to, for example, electrode pads of the head gimbal assembly 158, and are electrically connected to the magnetic head.

[0078] The magnetic recording device 150 according to the embodiment includes a magnetic recording medium, a magnetic head according to the embodiment, a movable unit, a position control unit, and a signal processing unit. The movable unit allows the magnetic recording medium and the magnetic head to be relatively moved while being separated from each other or in contact with each other. The position control unit aligns the magnetic head with 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.

[0079] For example, the magnetic recording medium is a recording medium disk 180. The movable portion includes, for example, a head slider 159. The position control portion includes, for example, a head gimbal assembly 158.

[0080] The embodiments may include the following technical solutions. (Technical proposal 1) A first magnetic pole; A second magnetic pole; a magnetic element provided between the first magnetic pole and the second magnetic pole; A magnetic head comprising: The magnetic element includes: A first magnetic layer; a second magnetic layer provided between the first magnetic layer and the second magnetic pole; The magnetic head, A magnetic recording medium; Equipped with the magnetic element includes a midpoint between the first magnetic layer and the second magnetic layer in a first direction from the first magnetic pole to the second magnetic pole; The first ratio r1 and the second ratio r2 are -0.26×r1+0.60 ≦ r2 ≦ -0.26×r2+0.70 Fulfilling the first ratio r1 is a ratio of a second distance L2 between the first magnetic pole and the midpoint in the first direction to a first distance L1 between the first magnetic pole and the second magnetic pole in the first direction; The magnetic recording device, wherein the second ratio r2 is a ratio of the dynamic coercivity Hc0 of the magnetic recording medium to the average anisotropy magnetic field Hk of the magnetic recording medium.

[0081] (Technical proposal 2) The magnetic element includes: a third magnetic layer provided between the first magnetic pole and the first magnetic layer; a fourth magnetic layer provided between the first magnetic layer and the second magnetic layer; Further comprising: a first magnetic layer thickness along the first direction of the first magnetic layer is thicker than a third magnetic layer thickness along the first direction of the third magnetic layer; A magnetic recording device described in Technical Proposal 1, wherein a second magnetic layer thickness along the first direction of the second magnetic layer is thicker than a fourth magnetic layer thickness along the first direction of the fourth magnetic layer.

[0082] (Technical proposal 3) the first magnetic layer thickness is greater than the fourth magnetic layer thickness, The magnetic recording device described in Technical Proposal 2, wherein the second magnetic layer thickness is thicker than the third magnetic layer thickness.

[0083] (Technical proposal 4) The magnetic element includes: a first nonmagnetic layer provided between the first magnetic layer and the fourth magnetic layer; a second nonmagnetic layer provided between the fourth magnetic layer and the second magnetic layer; a third nonmagnetic layer provided between the first magnetic pole and the third magnetic layer; a fourth nonmagnetic layer provided between the third magnetic layer and the first magnetic layer; a fifth nonmagnetic layer provided between the second magnetic layer and the second magnetic pole; The magnetic recording device according to Technical Solution 2, further comprising:

[0084] (Technical proposal 5) the first nonmagnetic layer is in contact with the first magnetic layer and the fourth magnetic layer, the second nonmagnetic layer is in contact with the fourth magnetic layer and the second magnetic layer, the third nonmagnetic layer is in contact with the first magnetic pole and the third magnetic layer, the fourth nonmagnetic layer is in contact with the third magnetic layer and the first magnetic layer, The magnetic recording device described in Technical Proposal 4, wherein the fifth nonmagnetic layer is in contact with the second magnetic layer and the second magnetic pole.

[0085] (Technical proposal 6) the first nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the second nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the third nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the fourth nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; The magnetic recording device according to Technical Solution 4 or 5, wherein the fifth nonmagnetic layer contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0086] (Technical proposal 7) the first nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; the second nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the third nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; The magnetic recording device according to Technical Solution 4 or 5, wherein the fifth nonmagnetic layer contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0087] (Technical proposal 8) the first nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; the second nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the third nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; the fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; The magnetic recording device according to Technical Solution 4 or 5, wherein the fifth nonmagnetic layer contains at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0088] (Technical proposal 9) The magnetic recording device according to any one of Technical Solutions 1 to 8, wherein the first ratio r1 is equal to or greater than 0.35 and equal to or less than 0.7.

[0089] (Technical proposal 10) The magnetic recording device according to any one of Technical Solutions 1 to 9, wherein the second ratio r2 is equal to or greater than 0.45 and equal to or less than 0.56.

[0090] (Technical proposal 11) a product of a first saturation magnetization of the first magnetic layer and a first magnetic layer thickness of the first magnetic layer in the first direction is equal to or greater than 9 nmT and equal to or less than 19 nmT; A magnetic recording device described in Technical Proposal 1, in which the product of the second saturation magnetization of the second magnetic layer and the second magnetic layer thickness of the second magnetic layer in the first direction is greater than or equal to 9 nmT and less than or equal to 19 nmT.

[0091] (Technical proposal 12) a product of a first saturation magnetization of the first magnetic layer and a thickness of the first magnetic layer is 9 nmT or more and 19 nmT or less; the product of the second saturation magnetization of the second magnetic layer and the second magnetic layer thickness is 9 nmT or more and 19 nmT or less; a product of a third saturation magnetization of the third magnetic layer and a thickness of the third magnetic layer is equal to or greater than 2 nmT and equal to or less than 10 nmT; The magnetic recording device described in Technical Solution 2 or 3, wherein the product of the fourth saturation magnetization of the fourth magnetic layer and the fourth magnetic layer thickness is 2 nmT or more and 10 nmT or less.

[0092] (Technical proposal 13) The average anisotropic magnetic field Hk is 17300 Oe or more and 21200 Oe or less, The magnetic recording device according to any one of Technical Solutions 1 to 12, wherein the dynamic coercivity Hc0 is 7500 Oe or more and 11000 Oe or less.

[0093] (Technical proposal 14) The magnetic recording device according to any one of Technical Solutions 1 to 13, wherein the first distance L1 is not less than 15 nm and not more than 50 nm.

[0094] (Technical proposal 15) the thickness of the first magnetic layer is 5 nm or more and 15 nm or less; The thickness of the second magnetic layer is 5 nm or more and 15 nm or less, the third magnetic layer has a thickness of 1 nm or more and 5 nm or less; The magnetic recording device described in Technical Solution 2 or 3, wherein the thickness of the fourth magnetic layer is 1 nm or more and 5 nm or less.

[0095] (Technical proposal 16) The magnetic recording medium includes a magnetic recording layer, The magnetic recording device according to any one of Technical Solutions 1 to 15, wherein the magnetic recording layer has a thickness of 5 nm or more and 50 nm or less.

[0096] (Technical proposal 17) The magnetic recording device described in Technical Solution 16, wherein the magnetic recording layer is a perpendicular magnetization film.

[0097] (Technical proposal 18) the magnetic head includes a medium facing surface; The magnetic recording device according to any one of Technical Solutions 1 to 16, wherein an angle between the first direction and the medium facing surface is not less than 0 degrees and not more than 40 degrees.

[0098] (Technical proposal 19) Further comprising an element circuit, the element circuit is capable of supplying an element current to the magnetic element, the element current being oriented from the first magnetic layer to the second magnetic layer; The magnetic recording device according to any one of Technical Solutions 1 to 18, wherein an alternating magnetic field is generated from the magnetic element when the element current is supplied to the magnetic element.

[0099] (Technical proposal 20) Further comprising a recording circuit; The magnetic head further includes a coil. the recording circuit is capable of supplying a recording current to the coil; 20. The magnetic recording device according to any one of Technical Solutions 1 to 19, wherein information corresponding to the recording current is recorded on the magnetic recording medium.

[0100] According to the embodiment, it is possible to provide a magnetic recording device capable of improving the recording density.

[0101] In this specification, "vertical" and "parallel" do not only mean strictly vertical and strictly parallel, but also include, for example, variations in the manufacturing process, and may mean substantially vertical and substantially parallel.

[0102] The above describes the embodiments of the present invention with reference to specific examples. However, the present invention is not limited to these specific examples. For example, the specific configurations of each element included in the magnetic head and magnetic recording device, such as the magnetic pole, magnetic element, magnetic layer, non-magnetic layer, and control unit, are included in the scope of the present invention as long as a person skilled in the art can implement the present invention in the same way and obtain the same effect by appropriately selecting from the known range.

[0103] Any combination of two or more elements of each embodiment, within the scope of technical feasibility, is also included within the scope of the present invention as long as it includes the gist of the present invention.

[0104] In addition, all magnetic recording devices that can be implemented by a person skilled in the art by making appropriate design modifications based on the magnetic recording device described above as an embodiment of the present invention also fall within the scope of the present invention as long as they include the gist of the present invention.

[0105] In addition, within the scope of the concept of the present invention, a person skilled in the art may conceive of various modifications and alterations, and it will be understood that these modifications and alterations also fall within the scope of the present invention.

[0106] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0107] 20: magnetic element, 20D: element circuit, 21-24: first to fourth magnetic layers, 30D: recording circuit, 30F: medium facing surface, 30c: coil, 30i: insulating section, 31, 32: first and second magnetic poles, 33: shield, 41-45: first to fifth non-magnetic layers, 60: recording section, 70: reproducing section, 71: magnetic reproducing element, 72a, 72b: first and second reproducing magnetic shields, 75: control section, 80: magnetic recording medium, 81: magnetic recording layer, 82: medium substrate, 83: magnetization, 85: medium 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, Iw: recording current, L1, L2: first and second distances, P1: midpoint, T1, T2: first and second terminals, Tc1, Tc2: first and second coil terminals, V20: element voltage, W1, W2: first and second wiring, ic: element current, je: electron current, r1, r2: first and second ratios, t1 to t4: first to fourth magnetic layer thicknesses, t41 to t45: first to fifth non-magnetic layer thicknesses

Claims

1. A first magnetic pole; A second magnetic pole; a magnetic element provided between the first magnetic pole and the second magnetic pole; A magnetic head comprising: The magnetic element includes: A first magnetic layer; a second magnetic layer provided between the first magnetic layer and the second magnetic pole; The magnetic head, A magnetic recording medium; Equipped with the magnetic element includes a midpoint between the first magnetic layer and the second magnetic layer in a first direction from the first magnetic pole to the second magnetic pole; The first ratio r1 and the second ratio r2 are -0.26×r1+0.60 ≦ r2 ≦ -0.26×r2+0.70 Fulfilling the first ratio r1 is a ratio of a second distance L2 between the first magnetic pole and the midpoint in the first direction to a first distance L1 between the first magnetic pole and the second magnetic pole in the first direction; The magnetic recording apparatus, wherein the second ratio r2 is a ratio of the dynamic coercivity Hc0 of the magnetic recording medium to the average anisotropy magnetic field Hk of the magnetic recording medium.

2. The magnetic element includes: a third magnetic layer provided between the first magnetic pole and the first magnetic layer; a fourth magnetic layer provided between the first magnetic layer and the second magnetic layer; Further comprising: a first magnetic layer thickness along the first direction of the first magnetic layer is thicker than a third magnetic layer thickness along the first direction of the third magnetic layer; 2 . The magnetic recording device according to claim 1 , wherein a second magnetic layer thickness of the second magnetic layer along the first direction is thicker than a fourth magnetic layer thickness of the fourth magnetic layer along the first direction.

3. The magnetic element includes: a first nonmagnetic layer provided between the first magnetic layer and the fourth magnetic layer; a second nonmagnetic layer provided between the fourth magnetic layer and the second magnetic layer; a third nonmagnetic layer provided between the first magnetic pole and the third magnetic layer; a fourth nonmagnetic layer provided between the third magnetic layer and the first magnetic layer; a fifth nonmagnetic layer provided between the second magnetic layer and the second magnetic pole; The magnetic recording device of claim 2 , further comprising:

4. the first nonmagnetic layer is in contact with the first magnetic layer and the fourth magnetic layer, the second nonmagnetic layer is in contact with the fourth magnetic layer and the second magnetic layer, the third nonmagnetic layer is in contact with the first magnetic pole and the third magnetic layer, the fourth nonmagnetic layer is in contact with the third magnetic layer and the first magnetic layer, The magnetic recording device according to claim 3 , wherein the fifth nonmagnetic layer is in contact with the second magnetic layer and the second magnetic pole.

5. the first nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the second nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the third nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the fourth nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; 4. The magnetic recording device according to claim 3, wherein the fifth nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

6. the first nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; the second nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the third nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; 5. The magnetic recording device according to claim 4, wherein the fifth nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

7. the first nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; the second nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; the third nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W; the fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag; 4. The magnetic recording device according to claim 3, wherein the fifth nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

8. The average anisotropic magnetic field Hk is equal to or greater than 17,300 Oe and equal to or less than 21,200 Oe, 8. The magnetic recording device according to claim 1, wherein the dynamic coercivity Hc0 is equal to or greater than 7500 Oe and equal to or less than 11000 Oe.

9. Further comprising an element circuit, the element circuit is capable of supplying an element current to the magnetic element, the element current being oriented from the first magnetic layer to the second magnetic layer; 2. The magnetic recording device according to claim 1, wherein an alternating magnetic field is generated from the magnetic element when the element current is supplied to the magnetic element.

10. Further comprising a recording circuit; The magnetic head further includes a coil. the recording circuit is capable of supplying a recording current to the coil; 2. The magnetic recording device according to claim 1, wherein information corresponding to the recording current is recorded on the magnetic recording medium.

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