JP5890983B2 - Magnetic recording device - Google Patents

Description

  The present invention relates to a magnetic recording head having a function of inducing magnetization reversal by applying a high frequency magnetic field to a magnetic recording medium.

In recent years, a magnetic recording / reproducing apparatus such as an HDD (Hard Disk Drive) has been required to rapidly increase the recording density of about 40% per year, and the surface recording density is expected to reach 1 Tbits / inch ² around 2013. Has been.

  In order to improve the surface recording density, it is necessary to miniaturize the magnetic recording head and the reproducing head and to reduce the particle size of the magnetic recording medium. However, since the recording magnetic field strength decreases due to the miniaturization of the magnetic recording head, it is predicted that the recording capability will be insufficient. In addition, since the problem of thermal fluctuation becomes obvious when the particle size of the magnetic recording medium becomes finer, it is necessary to increase the coercive force and anisotropic energy at the same time as making the particle size finer. It becomes difficult. Therefore, in order to improve the surface recording density, it is the key to improve the recording ability.

  Thus, an assist recording method has been proposed in which the coercive force of the magnetic recording medium is temporarily reduced only when information is recorded by applying heat or a high-frequency magnetic field. Patent Document 1 below describes an assist recording method by applying “heat”.

  On the other hand, an assist recording method called “microwave assist recording (MAMR)” by applying a high-frequency magnetic field has recently attracted attention. In MAMR, a high-frequency magnetic field in a strong microwave band is applied to a nanometer order region to locally excite a recording medium, and a magnetization reversal magnetic field is reduced to record information. Since this method uses magnetic resonance, the effect of reducing the magnetization reversal magnetic field cannot be sufficiently obtained unless a strong high-frequency magnetic field proportional to the anisotropic magnetic field of the recording medium is used.

  Patent Document 2 listed below discloses a high-frequency oscillator having a structure in which a laminated film is sandwiched between electrodes, similar to a GMR element (giant magnetoresistive element) in order to generate a high-frequency assist magnetic field. The high-frequency oscillator can generate a minute high-frequency oscillating magnetic field by injecting conduction electrons having spin fluctuations generated in the GMR structure into the magnetic material via the non-magnetic material.

  In Non-Patent Document 1 below, similarly to Patent Document 2, microwave oscillation using spin torque is reported.

  In Non-Patent Document 2 below, a micro-frequency magnetic field generation layer (hereinafter referred to as FGL) that rotates at high speed by spin torque is disposed near a magnetic recording medium adjacent to a main magnetic pole of a perpendicular magnetic head. A technique for generating information on a magnetic recording medium that generates a wave (a high-frequency magnetic field) and has a large magnetic anisotropy is disclosed.

  In Non-Patent Document 3 below, an oscillator is disposed between a main magnetic pole of a magnetic recording head and a shield on the rear side (trailing side) of the main magnetic pole, and the rotation direction of the high-frequency magnetic field is changed according to the recording magnetic field polarity. Thus, a technique for efficiently assisting the magnetization reversal of the magnetic recording medium is disclosed.

 The shield is also widely used in the magnetic heads of current products, and is used to improve the recording magnetic field gradient in the head traveling direction in the current products. On the other hand, in MAMR, a shield is used to change the rotation direction of the high-frequency magnetic field of the oscillator in accordance with the recording magnetic field polarity.

  In order to efficiently cause the magnetization reversal, it is desirable that the rotation direction of the high-frequency magnetic field of the oscillator is the same as the direction of the magnetization precession of the magnetic recording medium to be reversed. Therefore, in the technique described in Non-Patent Document 3, magnetization reversal can be assisted by using a high-frequency magnetic field in the rotation direction that efficiently causes magnetization reversal.

  For the sake of simplicity, hereinafter, a microwave assist head in which a high-frequency oscillator is disposed between the main magnetic pole and the trailing shield will be referred to as a MAMR head, and a portion composed of the main magnetic pole and the trailing shield excluding the high-frequency oscillator will be referred to as a recording head. Call.

JP-A-7-244801 JP 2005-025831 A

Nature, Vol. 425, pp.380 (2003) “Microwave Assisted Magnetic Recording”, J-G. Zhu et.al, IEEE trans. Magn., Vol. 44, NO.1, pp.125 (2008) “Medium damping constant and performance characteristics in microwave assisted magnetic recording with circular as field”, Y. Wang et. Al, Journal of Applied Physics, Vol. 105, pp.07B902 (2009)

In order to realize a recording density of about 1 Tbits / inch ^{2 by} MAMR, a magnetic recording medium is locally brought into a magnetic resonance state by irradiating a region of nanometer order with a strong high-frequency magnetic field, and a magnetization reversal magnetic field is reduced. Information needs to be recorded.

In the techniques disclosed in Patent Documents 1 and 2 and Non-Patent Document 1, a high recording density of about 1 Tbits / inch ² is realized because the frequency of the oscillating high-frequency magnetic field is too low or the magnetic field strength is too weak. It is difficult to do.

It has been reported that if the techniques disclosed in Non-Patent Documents 2 and 3 are used, a recording density of ¹ Tbits / inch ² or more may be realized. Therefore, the present inventors also examined how much the recording density could be improved by using the MAMR system technique described in Non-Patent Document 3. Specifically, the recording magnetic field strength generated from the main magnetic pole of the recording head and the high-frequency magnetic field strength generated from the high-frequency magnetic field generation layer were calculated by micromagnetic simulation using an LLG (Landau-Liftshitz-Gilbert-Langevin equations) equation. Two assumptions are assumed for the calculation: a realistic environment that considers the magnetic interaction between the recording head and the high-frequency magnetic field generation layer, and a case where the magnetic interaction is virtually ignored. did. The MAMR head structure is described in Non-Patent Document 2 and Non-Patent Document 3.

  As a result of the simulation, when the magnetic coupling between the recording head and the high-frequency magnetic field generating layer is considered, a sufficiently strong recording magnetic field strength is generated from the main magnetic pole of the recording head, but the high-frequency magnetic field from the high-frequency magnetic field generating layer is generated. The strength became very small. On the other hand, when the magnetic coupling between the main recording head and the high-frequency magnetic field generating layer is not taken into consideration, the high-frequency magnetic field as high as about 2 kOe from the high-frequency magnetic field generating layer as described in Non-Patent Documents 2 and 3. Occurred. This is because the high-frequency magnetic field generation layer of the MAMR head used in this calculation is in contact with the main magnetic pole, so that the magnetic coupling between the high-frequency magnetic field generation layer and the main magnetic pole is large, and the oscillation of the high-frequency magnetic field generation layer is hindered. It was because it was done. Therefore, in reality, due to the influence of magnetic exchange coupling between the recording head and the high frequency magnetic field generating layer, the magnetization of the high frequency magnetic field generating layer is fixed, and a sufficient high frequency magnetic field strength cannot be realized.

  In order to suppress the magnetic coupling between the high frequency magnetic field generating layer and the main magnetic pole of the recording head, it is considered that the high frequency magnetic field generating layer may be provided at the trailing end. However, in this case as well, the high frequency magnetic field strength is not improved. This is because the oscillation of the high frequency magnetic field generation layer is hindered by the magnetic coupling between the high frequency magnetic field generation layer and the trailing shield. Therefore, it is necessary to reduce both the magnetic coupling between the high-frequency magnetic field generating layer and the main magnetic pole and the magnetic coupling between the high-frequency magnetic field generating layer and the trailing shield.

  Furthermore, it has been found through examination that, when the high-frequency magnetic field generating layer is arranged at a position far from the main magnetic pole, there is a problem that the effect of improving the effective recording magnetic field strength by applying the high-frequency magnetic field is severely attenuated. . Actually, using a MAMR head in which the distance between the high-frequency magnetic field generating layer and the main pole is about 30 nm, numerical calculation is performed based on the assumption that the magnetic coupling between the high-frequency magnetic field generating layer and the recording head is virtually small. As a result, the signal quality of the recorded signal was very poor. This is because the position where the high-frequency magnetic field is highest is considerably farther than the main pole when the position of the high-frequency magnetic field generation layer is too far from the main pole.

  As described above, even if the high frequency magnetic field generating layer is too close to or far from the main magnetic pole, the high frequency magnetic field strength and the effective recording magnetic field strength are attenuated, and a high recording density cannot be realized.

  The present invention has been made to solve the above-described problems, and provides a magnetic recording head capable of obtaining a high-frequency magnetic field strength and an effective recording magnetic field strength in microwave-assisted recording using an oscillator that generates a high-frequency magnetic field. It aims to be realized.

  A magnetic recording head according to the present invention includes a main magnetic pole, an oscillator having a high-frequency magnetic field generating layer for applying a high-frequency magnetic field to a magnetic recording medium, and a trailing shield provided on the trailing side of the main magnetic pole. Both the distance between the generation layer and the main magnetic pole and the distance between the high-frequency magnetic field generation layer and the trailing shield are 3 nm or more.

  According to the magnetic recording head of the present invention, a high recording density can be realized by appropriately controlling the interaction between the high-frequency magnetic field generating layer and the recording head.

1 is a diagram illustrating a configuration example of a magnetic recording apparatus according to a first embodiment. 2 is a diagram illustrating a detailed configuration of a recording head unit 100. FIG. A schematic diagram of the main magnetic pole 120 and the oscillator 110 when viewed from the surface facing the leading direction is shown. It is a figure which shows the structural example of the conditions B shown in below-mentioned FIG. It is a figure which shows the structural example of the conditions C shown in below-mentioned FIG. It is a figure which shows the relationship between the high frequency magnetic field intensity | strength (Hac) which generate | occur | produces from FGL111 when the film thickness and position of FGL111 are changed, and d_FM and d_FT. It is a figure which shows the range which satisfy | fills Formula 1. FIG. FIG. 6 is a diagram illustrating a range that satisfies Expression 2. 6 is a diagram illustrating a configuration example of a magnetic recording apparatus according to a second embodiment. FIG. 6 is a diagram illustrating a detailed configuration of a recording head unit 100 according to Embodiment 2. FIG. FIG. 6 is a diagram illustrating a detailed configuration of a recording head unit 100 according to a third embodiment. It is a figure which shows the relationship between the amplification factor of the effective magnetic field intensity of a MAMR head, and d_FM. 4 is a schematic diagram of a magnetic flux distribution of a recording magnetic field generated from the main magnetic pole 120 toward the magnetic recording medium 300. FIG. The relationship between a magnetic field angle and a down track direction position is shown. The relationship between the amplification factor of the effective magnetic field strength by high frequency assist and the value obtained by normalizing d_FM by the ratio of TG and HUS is shown. FIG. 6 is a diagram illustrating a configuration example of a magnetic recording / reproducing head according to a fourth embodiment. It is a figure which shows the structural example of the magnetic recording / reproducing apparatus 1000 which concerns on Embodiment 5. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding, the same functional parts are denoted by the same reference numerals in the following drawings.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration example of a magnetic recording apparatus according to Embodiment 1 of the present invention. Here, an outline of the periphery of the magnetic recording / reproducing head is shown. It should be noted that the drawings described in this specification show the overall configuration of the magnetic recording / reproducing head, so that the scale of each part is not necessarily the same as the actual scale of the head. The same applies to other parts.

  The magnetic recording / reproducing head is a recording / reproducing separation head including a recording head unit 100 and a reproducing head unit 200.

  The recording head unit 100 includes an oscillator 110, a main magnetic pole 120, a sub magnetic pole 130a, a trailing shield 130b, and a coil 160. The oscillator 110 generates a high frequency magnetic field. The main magnetic pole 120 generates a recording head magnetic field. The trailing shield 130b is provided to control the magnetization rotation direction of the oscillator 110. The coil 160 and the sub magnetic pole 130 a excite a magnetic field on the main magnetic pole 120.

  The traveling direction of the magnetic recording / reproducing head with respect to the medium is referred to as a leading direction, and the direction opposite to the traveling direction of the magnetic recording / reproducing head with respect to the medium is referred to as a trailing direction. Although not shown in FIG. 1, a side shield may be provided outside the main pole 120 in the track width direction. The side shields may be provided on both sides of the main magnetic pole 120, or may be provided only on either the outer side or the inner side.

  In FIG. 1, when viewed from the traveling direction of the magnetic recording / reproducing head with respect to the magnetic recording medium 300, the reproducing head unit 200 is disposed at the head and the recording head unit 100 is disposed behind. The arrangement may be reversed so that the recording head unit 100 is at the top and the reproducing head unit 200 is at the rear as viewed from the top.

  The reproducing head unit 200 includes a reproducing sensor 210, a lower magnetic shield 220, and an upper magnetic shield 230. The reproduction sensor 201 can adopt any configuration as long as it can play a role of reproducing a recording signal. The configuration of the regenerative sensor 210 may be a regenerative sensor having a so-called GMR (Giant Magneto-Resistive) effect, a regenerative sensor having a TMR (Tunneling Magneto-Resitive) effect, or an EMR (Electro Mechanical Resonant) effect. A regeneration sensor may be used. Also, a so-called differential reproduction sensor having two or more reproduction sensors that respond to an external magnetic field with opposite polarities may be used. Since the lower magnetic shield 220 and the upper magnetic shield 230 play an important role in improving the reproduction signal quality, it is preferable to provide them. Although not specifically shown in FIG. 1, the upper magnetic shield 230 can also serve as an auxiliary magnetic pole of the recording head unit 100.

  FIG. 2 is a diagram illustrating a detailed configuration of the recording head unit 100. The oscillator 110 includes an FGL 111, an intermediate layer 112, and a spin injection fixed layer 113 in order from the main magnetic pole side. The FGL 111 generates a high frequency magnetic field. The intermediate layer 112 is configured using a material having high spin permeability. The spin injection pinned layer 113 gives a spin torque to the FGL 111. Further, in order to appropriately control the distance (d_FM) between the FGL 111 and the main magnetic pole 120, a magnetic coupling blocking layer 140 set to an appropriate film thickness is provided between the FGL 111 and the main magnetic pole 120.

  In the configuration example in the first embodiment, the thicknesses of the respective layers are the magnetic coupling blocking layer 140 = 7 nm, FGL111 = 10 nm, the intermediate layer 112 = 3 nm, and the spin injection fixed layer 113 = 10 nm. Therefore, the distance (TG) between the main magnetic pole 120 and the trailing shield 130b is 30 nm.

In the first embodiment, the material of the main magnetic pole 120 is Fe ₇₀ Co ₃₀ and the saturation magnetization (M_MP) is 2.4T. The material of the trailing shield 130b is NiFe, and the saturation magnetization (M_TS) is 1.2T. The material of the main magnetic pole 120 and the trailing shield 130b is not particularly limited in addition to being a magnetic material as long as it satisfies the formulas 1 and 2 described later. A larger value is more advantageous for generating a higher recording magnetic field strength. Further, the material of the trailing shield 130b is advantageous in that the magnetic permeability is higher because the magnetic field application response to the FGL 111 accompanying the reversal of the recording current polarity becomes faster.

  In the first embodiment, the material of the magnetic coupling interruption layer 140 is Ta. The material of the magnetic coupling blocking layer 140 is not particularly limited except that it is a non-magnetic conductive material, and is arbitrarily selected from, for example, Au, Ag, Pt, Ta, Ir, Al, Si, Ge, Ti, etc. can do.

In the first embodiment, the material of the FGL 111 is Fe ₇₀ Co ₃₀ . The saturation magnetization of Fe ₇₀ Co ₃₀ is 2.4 T, and a high frequency magnetic field can be generated. The material of the FGL 111 is a magnetic material, and can play a role as the FGL 111 as long as it is within a range that satisfies formulas 1 and 2 described later. For example, in addition to the FeCo alloy, a Heusler alloy such as NiFe alloy, CoFeGe, CoMnGe, CoFeAl, CoFeSi, CoMnSi, and CoFeSi, a Re-TM-based amorphous alloy such as TbFeCo, and a CoCr-based alloy may be used. Further, a material having negative vertical anisotropy energy such as CoIr or a material having positive vertical anisotropy energy such as Co / Pt may be used. The FGL 111 may have a configuration in which a plurality of layers of different materials are stacked, or may be a combination of materials having different saturation magnetization and different magnitudes of anisotropic energy.

  In the first embodiment, the material of the intermediate layer 112 is Cu. The material of the intermediate layer 112 is preferably a nonmagnetic conductive material. For example, Au, Ag, Pt, Ta, Ir, Al, Si, Ge, Ti, or the like can be used.

  In the first embodiment, the material of the spin injection fixed layer 113 is Co / Pt. Further, the Co / Pt perpendicular anisotropy magnetic field Hk used in Embodiment 1 is 8 kOe. By using a material having vertical anisotropy as the material of the spin injection fixed layer 113, the oscillation of the FGL 111 can be stabilized. For example, in addition to Co / Pt, it is preferable to use an artificial magnetic material such as Co / Ni, Co / Pd, or CoCrTa / Pd. Further, although the oscillation stability is slightly lost, a material similar to that of the FGL 111 can be used.

  Although not shown in FIGS. 1 to 2, a cap layer for controlling the unevenness and magnetic characteristics of the spin injection pinned layer 113 may be provided on the spin injection pinned layer 113. The cap layer is a nonmagnetic conductive material. For example, Au, Ag, Pt, Ta, Ir, Al, Si, Ge, Ti, or the like can be used.

  FIG. 3 is a schematic diagram of the main magnetic pole 120 and the oscillator 110 when viewed from the surface facing the leading direction. The track width (Two) of the oscillator 110 is 40 nm, and the track width (Pw) of the main magnetic pole 120 is 45 nm. The values of Two and Pw can be arbitrarily set so as to obtain a high recording density. The width (SHo) in the element height direction of the oscillator is 40 nm. The value of SHo can be appropriately designed so that an appropriate high-frequency magnetic field strength and frequency can be obtained from the FGL 111. A length (TH) substantially perpendicular to the bottom surface in the height direction of the main magnetic pole 120 is 60 nm. The value of TH can be appropriately designed so that an appropriate recording magnetic field strength can be obtained. Furthermore, the size of the track width spread at a position above TH as viewed from the air bearing surface can also be set appropriately.

  The feature of the present invention is that the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the FGL 111 and the trailing shield 130b can be suppressed. As a result, the high-frequency magnetic field can be stably applied to the medium without causing deterioration of the high-frequency magnetic field due to the inhibition of the oscillation of the FGL 111. Hereinafter, specific conditions and effects for suppressing the magnetic coupling between the FGL 111 and the recording head unit 100 will be described.

  In the present invention, the distance (d_FM) between the FGL 111 and the main magnetic pole 120 and the distance (d_FT) between the FGL 111 and the trailing shield 130b are both 3 nm or more. The d_FM in the configuration example described with reference to FIG. 2 is substantially 7 nm because it is substantially the thickness of the magnetic coupling blocking layer 140. Further, d_FT is 13 nm because it is substantially the sum of the film thicknesses of the intermediate layer 112 and the spin injection fixed layer 113. Therefore, in the configuration example described in FIG. 2, both d_FM and d_FT are 3 nm or more.

  In the following, in order to verify the effect and the range obtained by setting d_FM and d_FT in this way, the configuration example shown in FIG. 2 is referred to as condition A, and for comparison, the conditions B and FIG. Numerical calculation was performed by setting the condition C shown in FIG. In order to freely control d_FM and d_FT, the numerical calculation is performed on the assumption that the spin torque can be applied to the FGL 111 without the intermediate layer 112 and the spin injection fixed layer 113 virtually. Therefore, in FIGS. 4 to 5, the intermediate layer 112 or the spin injection fixed layer 113 may not exist. TG was fixed at 30 nm, and the film thickness of FGL111 was 10 nm.

  FIG. 4 is a diagram illustrating a configuration example of the condition B illustrated in FIG. 6 described later. In Condition B, d_FM is 2 nm, and the magnetic coupling interruption layer 140 is disposed on the main magnetic pole 120 side. Therefore, d_FM = 2 nm and d_FT = 18 nm.

  FIG. 5 is a diagram illustrating a configuration example of the condition C illustrated in FIG. 6 described later. Under condition C, d_FM is 1 nm, and the magnetic coupling blocking layer 140 is disposed on the trailing shield 130b side. Therefore, d_FM = 19 nm and d_FT = 1 nm.

  FIG. 6 is a diagram showing the relationship between the high frequency magnetic field intensity (Hac) generated from the FGL 111 when the film thickness and position of the FGL 111 are changed, and d_FM and d_FT. The high frequency magnetic field intensity indicates a value applied to the magnetic recording medium 300.

  In the configuration examples of the conditions A to C, the saturation magnetization (M_FGL) and M_MP of the FGL 111 are both 2.4T and M_TS is 1.2T. In addition, the results of studies on a structure in which M_FGL is 1.2T and M_MP is 1.8T are also shown. The condition D will be described again in the second embodiment described later.

  According to the data shown in FIG. 6, it can be seen that, under any condition, when d_FM and d_FT are 3 nm or less, Hac is greatly attenuated. This is because when the FGL 111 and the main magnetic pole 120 or the FGL 111 and the trailing shield 130b are magnetically coupled, the magnetization of the FGL 111 is fixed and the oscillation stops. From this result, it can be seen that if d_FM and d_FT are 3 nm or more, attenuation of Hac can be suppressed.

  In the data example shown in FIG. 6, M_MP, M_FGL, and M_TS are fixed. However, depending on the ratio between them, there is a possibility that d_FM and d_FT need to be secured larger. For example, it is considered that when the ratio of M_MP to M_FGL changes, the magnetic coupling between the main magnetic pole 120 and the FGL 111 changes. Similarly, it is considered that when the ratio of M_TS to M_FGL changes, the magnetic coupling between the FGL 111 and the trailing shield 130b changes.

  Therefore, in order to stably suppress the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the FGL 111 and the trailing shield 130b even if the values of M_MP, M_FGL, and M_TS change, It is considered that d_FM and d_FT may be configured to satisfy 1 and Equation 2.

d_FM ≧ 3 (nm) × M_MP / M_FGL (Formula 1)
d_FT ≧ 3 (nm) × M_TS / M_FGL (Expression 2)

  Equations 1 and 2 are based on the fact that the smaller the M_FGL, the more easily the FGL 111 is affected by magnetic coupling, and the smaller the saturation magnetization of the main pole 120 and the trailing shield 130b, the smaller the magnetic coupling magnetic field. Yes. Actually, in the data example shown in FIG. 6, under the condition that M_FGL is 1.2T, Hac is attenuated even when d_FM and d_FT are relatively large.

  FIG. 7 is a diagram illustrating a range that satisfies Equation 1. In FIG. In FIG. 7, it is assumed that the condition of Expression 2 is satisfied. FIG. 8 is a diagram illustrating a range that satisfies Expression 2. In FIG. In FIG. 8, it is assumed that the condition of Formula 1 is satisfied. As shown in FIGS. 7 and 8, it can be seen that if the range satisfies Expressions 1 and 2, Hac is not attenuated and high Hac can be realized.

  In addition, as shown in FIGS. 7-8, when M_FGL falls. It can be seen that Hac is reduced overall. This is because the maximum Hac realizable in each configuration is proportional to M_FGL. For example, although not shown in FIG. 7, with a configuration in which M_FGL is 0.6T, Hac is only about 0.5 kOe even at the maximum, and the reversal of the medium magnetization cannot be assisted efficiently. Since Hac is preferably about 1 kOe at least to assist the magnetization reversal of the medium, M_FGL is preferably 1.0 T or more in order to maintain this Hac.

<Embodiment 1: Summary>
As described above, the magnetic recording / reproducing head according to the first embodiment can suppress the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the trailing shield 130b and the FGL 111. As a result, a MAMR head equipped with the oscillator 110 capable of generating high Hac can be realized, and high recording density can be achieved.

<Embodiment 2>
FIG. 9 is a diagram illustrating a configuration example of the magnetic recording apparatus according to the second embodiment of the present invention. Here, as in FIG. 1, the outline of the periphery of the magnetic recording / reproducing head is shown. In the second embodiment, the configuration other than the oscillator 110 and the magnetic coupling blocking layer 140 is the same as that of the first embodiment, and therefore, the following description will focus on the differences.

  In the second embodiment, the stacking order of the FGL 111, the intermediate layer 112, and the spin injection fixed layer 113 is opposite to that in the first embodiment. The magnetic coupling blocking layer 140 is provided not between the FGL 111 and the main magnetic pole 120 but between the FGL 111 and the trailing shield 130b.

  FIG. 10 is a diagram illustrating a detailed configuration of the recording head unit 100 according to the second embodiment. In the second embodiment, the spin injection pinned layer 113, the intermediate layer 112, the FGL 111, and the magnetic coupling blocking layer 140 are stacked in this order from the main magnetic pole 120 side. Further, as in the first embodiment, the thickness of each layer is adjusted so that both d_FM and d_FT are 3 nm or more. Thereby, the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the trailing shield 130b and the FGL 111 can be suppressed. Similarly to the first embodiment, if d_FM, d_FT, M_FGL, M_MP, and M_TS satisfy the relationship of Expression 1 and Expression 2, magnetic coupling can be more effectively suppressed.

  The material of the main pole 120 and the material of the trailing shield 130b are the same as in the first embodiment. The FGL 111 and the intermediate layer 112 are also the same material and film thickness as in the first embodiment, and only the positions of the respective layers are different. The material and characteristics of the spin injection fixed layer 113 are the same as those in the first embodiment, but the film thickness is 6 nm. The material and characteristics of the magnetic coupling blocking layer 140 are the same as those in the first embodiment, but the film thickness is 11 nm.

  With the configuration shown in FIG. 10, d_FM is 9 nm and d_FT is 11 nm, both of which are 3 nm or more. Also, the right sides of Equation 1 and Equation 2 are 3.0 and 1.5, respectively, and satisfy these relationships.

  6 to 7, the configuration shown in FIG. As can be seen from FIGS. 6 to 7, also in the second embodiment, the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the trailing shield 130b and the FGL 11 are suppressed, and the attenuation of Hac is suppressed. be able to.

  In the second embodiment, unlike the first embodiment, since the spin injection pinned layer 113 is positioned near the main magnetic pole 120, the magnetic field strength from the main magnetic pole 120 applied to the spin injection pinned layer 113 is large, and the recording current is increased. There is an advantage that the magnetization reversal of the spin injection fixed layer 113 in accordance with the change in polarity is quick. On the other hand, since the FGL 111 is located farther from the main magnetic pole 120 than the configuration of the first embodiment, the recording transition position is formed at a position where the Hac is low, and the effect of improving the effective recording magnetic field strength by applying the Hac is reduced.

<Embodiment 3>
FIG. 11 is a diagram showing a detailed configuration of the recording head unit 100 according to the third embodiment of the present invention. The third embodiment is different from the first embodiment in that the film thickness of the spin injection fixed layer 113 of the oscillator 110 is 20 nm. Other configurations are the same as those in the first embodiment, but the magnetic recording medium 300 will be described in more detail in the third embodiment.

  The magnetic recording medium 300 includes a recording layer 301, an intermediate layer 302, and a soft magnetic underlayer 303 in order from the side close to the magnetic recording / reproducing head.

In Embodiment 3, the recording layer 301 is made of a CoCrPt-based alloy, has a film thickness of 15 nm, a saturation magnetization (Ms) of 300 emu / cc, and a perpendicular anisotropy energy of 4.5 × 10 ⁶ erg / cc. The material of the recording layer 301 may be other than the CoCrPt alloy, but is preferably a material having perpendicular magnetic anisotropy. The recording layer 301 can be composed of a plurality of layers having different perpendicular anisotropy energies.

  The intermediate layer 302 is provided in order to suppress magnetic coupling between the recording layer 301 and the soft magnetic underlayer 303. The material of the intermediate layer 302 in Embodiment 3 is Ru, but there is no restriction other than being a nonmagnetic material. The film thickness of the intermediate layer 302 is 25 nm.

  The soft magnetic underlayer 303 plays a role of improving the recording magnetic field applied from the main magnetic pole 120 to the recording layer 301. The material of the soft magnetic underlayer 303 in Embodiment 3 is CoFeTa. The material of the soft magnetic underlayer 303 is preferably a material having a high magnetic permeability, but a magnetic material can play a role of increasing the recording magnetic field strength applied to the recording layer 301.

  Layers other than the recording layer 301 and the soft magnetic underlayer 303 can be added to the magnetic recording medium 300. For example, a protective film may be provided on the recording layer 301 for the purpose of suppressing corrosion of the recording layer 301 and deterioration of characteristics due to direct contact between the recording layer 301 and the magnetic head slider.

  The distance between the magnetic recording / reproducing head and the recording layer 301 in FIG. 11 is 5 nm. The magnetic recording medium 300 may be a so-called continuous medium in which each bit exists continuously, or may be a so-called discrete track medium in which a non-magnetic area where the recording head cannot write information is provided between a plurality of tracks. . Also, a so-called patterned medium including a convex magnetic pattern and a non-magnetic material filling the concave portion between the magnetic patterns on the substrate may be used.

  In the third embodiment, in addition to suppressing the magnetic coupling between the FGL 111 and the main magnetic pole 120, which is a feature of the first and second embodiments, d_FM is set to 12 nm or less. With this configuration, it is possible to suppress a reduction in assist efficiency of the high-frequency magnetic field, which occurs when the distance between the FGL 111 and the main magnetic pole 120 is too large, and to keep the effective magnetic field strength high.

  FIG. 12 is a diagram showing the relationship between the amplification factor of the effective magnetic field strength of the MAMR head and d_FM. The effective magnetic field amplification factor is the ratio of the effective magnetic field strength when a high frequency magnetic field is applied to the effective magnetic field strength when no high frequency magnetic field is applied. The higher this ratio, the more effectively the high frequency assist is functioning.

  The d_FM is controlled by controlling the film thickness of the magnetic coupler fault 140, the spin injection fixed layer 113, and the intermediate layer 112. Also, assuming that these film thickness changes do not affect other than changing the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the FGL 111 and the trailing shield 130b, The high frequency magnetic field intensity and effective magnetic field generated from the FGL 111 were calculated.

  The distance (HUS) between the magnetic recording / reproducing head and the soft magnetic underlayer 303 is 45 nm, and the distance (TG) between the main magnetic pole 120 and the trailing shield 130b is 40 nm. For comparison, the recording magnetic field strength when HUS is changed to 20 nm and when TG is changed to 20 nm are also shown.

  Since the configuration shown in FIG. 11 is d_FM = 7 nm, it corresponds to the condition E in FIG. The effective magnetic field strength when the high frequency magnetic field is applied is amplified twice as much as when the high frequency magnetic field is not applied, and it is understood that a sufficient effect is obtained by applying the high frequency magnetic field.

  However, when d_FM is larger than 12 nm, the effective magnetic field amplification factor is severely attenuated. For example, under the conditions of HUS = 45 nm, TG = 40 nm, d_FM = 20 nm, the amplification factor is only about 1.2 times. Therefore, it is considered that the effect of improving the effective magnetic field by applying the high frequency magnetic field can be fully utilized by setting d_FM to 12 nm or less.

  As described in the first embodiment, when d_FM is smaller than 3 nm, the high-frequency magnetic field intensity itself is attenuated, so that the effective magnetic field gain becomes small. Therefore, d_FM needs to be 3 nm or less also in the third embodiment. For the same reason, it is more preferable to satisfy the expressions 1 and 2 in the third embodiment.

  FIG. 13 is a schematic diagram of the magnetic flux distribution of the recording magnetic field generated from the main magnetic pole 120 toward the magnetic recording medium 300. The reason why the effective magnetic field intensity is attenuated when d_FM is large will be described with reference to FIG. Actually, the magnetic flux also flows through the oscillator 110, but is omitted in FIG. 13 for the sake of simplicity.

  As can be seen from FIG. 13, the magnetic flux is applied to the recording layer 301 at an angle close to a right angle immediately below the main magnetic pole 120. The angle of the magnetic flux with respect to the film surface of the recording layer 301 is defined as a magnetic field angle θ. An angle perpendicular to the film surface is θ = 90 °.

  As the high frequency magnetic field is applied perpendicularly to the magnetization of the recording layer 301, the effective coercive force of the medium by the high frequency magnetic field assist decreases in principle. Therefore, the high frequency assist efficiency is better when the magnetization of the recording layer 301 is oriented in the direction perpendicular to the film surface.

  The magnetization direction of the recording layer 301 greatly depends on the magnetic field angle generated from the main magnetic pole 120. The closer the magnetic field angle is to 90 degrees, the higher the efficiency of high-frequency assist. When the magnetic field angle is 0 degrees, the effect disappears completely. Since the magnetic field angle of the magnetic field applied from the main magnetic pole 120 to the recording layer 301 is larger as it is closer to the main magnetic pole 120, the assist efficiency is improved and the amplification factor of the effective magnetic field strength is improved as the FGL 111 is closer to the main magnetic pole 120. is there. Therefore, by adopting a structure in which d_FM is 12 nm or less, it is possible to realize a structure having a high amplification factor of effective magnetic field strength by high frequency assist.

  FIG. 14 shows the relationship between the magnetic field angle and the position in the down track direction. The leading end of the main magnetic pole 120 on the trailing side is set to a down track direction position = 0. The larger the value of the position in the down track direction, the closer to the trailing shield 130b side. In FIG. 14, in addition to the conditions of HUS of 45 nm and TG of 40 nm, for comparison, the magnetic field angle when HUS is changed to 25 nm and when TG is changed to 20 nm are also shown.

  As can be seen from FIGS. 13 and 14, the magnetic field angle decreases as the magnetic pole moves from the main magnetic pole 120 side to the trailing shield side. This is because the magnetic flux flows toward the soft magnetic underlayer 303, which is a magnetic material, and the trailing shield 130b. On the other hand, since the high-frequency magnetic field applied from the FGL 111 to the recording layer 301 fluctuates at a high frequency, it is not affected by the soft magnetic underlayer 303 or the trailing shield 130b. Unlike the main magnetic pole 120, the high-frequency magnetic field is generated more from the side surface than the bottom surface of the FGL 111, so that the component in the film surface of the recording layer 301 is increased.

  12 and 14 exemplify three patterns of combinations of HUS and TG. However, it is considered that when these values change, the amplification factor of the effective magnetic field also changes. For example, as HUS decreases, the magnetic field angle increases and the effective magnetic field gain also changes. Therefore, even if the values of TG and HUS change, in order to stably increase the effective magnetic field amplification factor by the high-frequency magnetic field assist, it is considered that a configuration in which the range of d_FM satisfies the following formula 3 is sufficient. It is done.

    d_FM ≦ 12 × TG / HUS (Formula 3)

  With the configuration satisfying Expression 3, even if the values of TG and HUS change, the relationship between the effective magnetic field strength amplification factor and d_FM by applying a high-frequency magnetic field as shown in FIG. 12 can be maintained well. The basis of Equation 3 will be described later.

  FIG. 15 shows the relationship between the amplification factor of effective magnetic field strength by high frequency assist and the value obtained by normalizing d_FM by the ratio of TG and HUS (d_FM × HUS / TG). This normalized value is obtained by modifying Equation 3. As shown in FIG. 15, by satisfying Equation 3, even if the values of TG and HUS change, the effective magnetic field amplification factor can always be kept at 1.5 times or more.

  The condition E shown in FIG. 15 corresponds to the configuration example shown in FIG. As shown in the condition E, the amplification factor of the effective magnetic field strength by applying the high frequency magnetic field is about twice. Condition E satisfies Expression 3 because d_FM which is the left side of Expression 3 is 7 nm and 12 × TG / HUS which is the right side is 10.7.

  The reason why the relationship between the amplification factor of the effective magnetic field by high frequency assist and d_FM differs depending on the values of TG and HUS is as follows.

  As can be seen from FIG. 14, the magnetic field angle of the magnetic field applied from the main magnetic pole 120 to the recording layer 301 differs depending on the ratio of TG and HUS. The amount of magnetic flux flowing from the main pole 120 to the soft magnetic underlayer 303 increases as the HUS decreases. Further, the amount of magnetic flux flowing from the main magnetic pole 120 to the trailing shield 130b increases as the TG decreases. The magnetic field angle increases as the amount of magnetic flux flowing through the soft magnetic underlayer 303 increases, and the magnetic field angle decreases as the amount of magnetic flux flowing through the trailing shield 130b increases. Therefore, it can be said that the magnetic field angle changes depending on the ratio of TG and HUS.

  In addition, as shown in FIG. 12, when HUS / TG becomes large, it can be said that the amplification factor of the effective magnetic field tends to decrease as a whole. For this reason, it is considered desirable to keep the size of each part within the range of HUS / TG ≦ 2.25 as shown in FIG.

<Embodiment 3: Summary>
As described above, according to the third embodiment, by setting d_FM within a range of 12 nm or less, it is possible to maintain a high effective magnetic field gain. Furthermore, by satisfying Expression 3, even when the values of TG and HUS change, the effective magnetic field gain can be maintained high.

  In the third embodiment, the high frequency magnetic field caused by the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the trailing shield 130b and the FGL 111 is satisfied by satisfying the range of d_FM described in the first embodiment. The attenuation of the intensity itself is suppressed, and as a result, a high effective magnetic field intensity is obtained.

<Embodiment 4>
FIG. 16 is a diagram showing a configuration example of a magnetic recording / reproducing head according to Embodiment 4 of the present invention. In the fourth embodiment, since the configuration other than the oscillator 110 and the magnetic coupling blocking layer 140 is the same as that of the third embodiment, the following description focuses on the differences.

  In the fourth embodiment, the stacking order of the FGL 111, the intermediate layer 112, and the spin injection fixed layer 113 is opposite to that in the third embodiment. The magnetic coupling blocking layer 140 is provided not between the FGL 111 and the main magnetic pole 120 but between the FGL 111 and the trailing shield 130b. Furthermore, the thicknesses of the magnetic coupling blocking layer 140 and the spin injection pinned layer 113 are different from those in the third embodiment. The configuration of the magnetic recording medium 300 is the same as that of the third embodiment.

  In the fourth embodiment, in addition to the d_FM condition for suppressing the magnetic coupling between the FGL 111 and the main magnetic pole 120 and the magnetic coupling between the trailing shield 130b and the FGL 111 described in the second embodiment, the implementation is performed. Similar to Embodiment 3, the thickness of each layer is adjusted so that d_FM is 12 nm or less. Thereby, the amplification factor of the effective magnetic field by applying a high frequency magnetic field can be maintained at a high level. Similarly to the third embodiment, if d_FM, TG, and HUS satisfy the relationship of Expression 3, magnetic coupling can be more effectively suppressed.

  The material of the main pole 120 and the material of the trailing shield 130b are the same as in the first embodiment. The FGL 111 and the intermediate layer 112 are also the same material and film thickness as in the first embodiment, and only the positions of the respective layers are different. The material and characteristics of the spin injection fixed layer 113 are the same as those in the first embodiment, but the film thickness is 6 nm. The material and characteristics of the magnetic coupling blocking layer 140 are the same as those in the first embodiment, but the film thickness is 21 nm.

  With the configuration shown in FIG. 16, d_FM is 9 nm (≦ 12 nm). Since HUS and TG are the same as in Embodiment 3, Equation 3 is also satisfied. From FIG. 12, it can be seen that the amplification factor of the effective magnetic field in the fourth embodiment is about 1.8 times, and a large amplification factor can be realized.

<Embodiment 5>
FIG. 17 is a diagram illustrating a configuration example of a magnetic recording / reproducing apparatus 1000 according to the fifth embodiment of the present invention. The magnetic recording / reproducing head has been described in any of Embodiments 1 to 4, and is mounted on the head slider 600.

  In the magnetic recording / reproducing apparatus 1000, the magnetic recording medium 300 is rotated by the spindle motor 400, and the head slider 600 is guided onto the track of the magnetic recording medium 300 by the actuator 500. That is, the reproducing head and the recording head formed on the head slider 600 relatively move close to a predetermined recording position on the magnetic recording medium 300 by this mechanism, and sequentially write or read signals. The actuator 500 is preferably a rotary actuator.

  The recording signal is recorded on the magnetic recording medium 300 by the recording head through the signal processing system 700. The signal processing system 700 obtains the output of the reproducing head as a signal. When the reproducing head is moved onto a desired recording track, the position on the track can be detected by using the highly sensitive output from the reproducing head, and the position of the head slider 600 can be determined by controlling the actuator 500. .

  In FIG. 17, one head slider 600 and one magnetic recording medium 300 are shown, but a plurality of them may be provided. The magnetic recording medium 300 may record information with recording information on both sides. When recording information on both sides of the disk, the head slider 600 is disposed on both sides of the magnetic recording medium 300.

  100: Recording head section, 110: Oscillator, 111: High frequency magnetic field generation layer (FGL), 112: Intermediate layer, 113: Spin injection fixed layer, 120: Main magnetic pole, 130a: Sub magnetic pole, 130b: Trailing shield, 140: Magnetic coupling blocking layer, 160: coil, 200: reproducing head, 210: reproducing sensor, 220: lower magnetic shield, 230: upper magnetic shield, 300: magnetic recording medium, 301: recording layer, 302: intermediate layer, 303: Soft magnetic underlayer, 400: spindle motor, 500: actuator, 600: head slider, 700: signal processing system.

Claims (6)

A magnetic recording head;
A magnetic recording medium on which the magnetic recording head records information;
A signal processing unit for processing a signal read by the magnetic recording head;
With
The magnetic recording head includes:
A main pole for applying a magnetic field to the magnetic recording medium;
A trailing shield provided on the trailing side of the main pole;
An oscillator provided between the main pole and the trailing shield;
With
The oscillator has a high-frequency magnetic field generating layer that generates a high-frequency magnetic field composed of a magnetic material,
The distance between the high-frequency magnetic field generation layer and the main magnetic pole, and the distance between the high-frequency magnetic field generation layer and the trailing shield are both 3 nm or more,
The distance between the magnetic recording head and the soft magnetic underlayer of the magnetic recording medium with respect to the distance between the main magnetic pole and the trailing shield, and the distance between the main magnetic pole and the high-frequency magnetic field generating layer The magnetic recording apparatus is configured to be equal to or less than 12 nm when multiplied by the ratio. The distance between the high-frequency magnetic field generation layer and the main magnetic pole is multiplied by the ratio of the saturation magnetization of the high-frequency magnetic field generation layer to the saturation magnetization of the main magnetic pole, and is configured to be 3 nm or more, and
The distance between the high-frequency magnetic field generation layer and the trailing shield is configured to be 3 nm or more by multiplying the ratio of the saturation magnetization of the high-frequency magnetic field generation layer to the saturation magnetization of the trailing shield. The magnetic recording apparatus according to claim 1. The magnetic recording apparatus according to claim 2, wherein the high-frequency magnetic field generating layer has a saturation magnetization of 1.0 T or more. The ratio of the distance between the magnetic recording head and the soft magnetic underlayer of the magnetic recording medium to the distance between the main magnetic pole and the trailing shield is configured to be 2.25 or less. The magnetic recording apparatus according to claim 1. The oscillator is
In order from the side close to the main pole, the high-frequency magnetic field generation layer, the intermediate layer, the spin injection pinned layer is laminated,
The magnetic recording apparatus according to claim 1, further comprising a magnetic coupling interruption layer formed using a nonmagnetic material between the main magnetic pole and the high-frequency magnetic field generation layer. The oscillator is
In order from the side close to the main magnetic pole, the spin injection pinned layer, the intermediate layer, and the high-frequency magnetic field generating layer are stacked,
The magnetic recording apparatus according to claim 1, further comprising a magnetic coupling blocking layer formed using a nonmagnetic material between the trailing shield and the high-frequency magnetic field generating layer.

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