Reproducing head using anomalous hall effect, magnetic disk device, and magnetic storage device

Abstract

The present invention comprises: a ferromagnetic body 10 that exhibits an anomalous Hall effect; a first current terminal and a second current terminal (I+, I-) that supply an electrical current to the ferromagnetic body 10; a first voltage terminal and a second voltage terminal (V+, V-) that detect a voltage generated in the ferromagnetic body 10; and a resistance adjustment layer that lies either at an interface between the first current terminal / second current terminal and the ferromagnetic body, or between the first voltage terminal / second voltage terminal and the ferromagnetic body. The resistance adjustment layer includes a high-resistance region and a low-resistance region. The low-resistance region electrically conducts between the first current terminal / second current terminal and the ferromagnetic body, or between the first voltage terminal / second voltage terminal and the ferromagnetic body.

Description

Reproducing head using anomalous Hall effect, magnetic disk drive and magnetic storage device

[0001] The present invention relates to a read head, a magnetic disk drive, and a magnetic storage device that utilize the anomalous Hall effect.This application claims priority to Japanese Patent Application No. 2023-115437, filed on July 13, 2023, the contents of which are incorporated herein by reference.

[0002] As the areal recording density of magnetic recording devices (hard disks) increases, improvements in the characteristics of read heads are required. A read head is a component of a hard disk and is a magnetic sensor that reads magnetic information recorded on a magnetic recording medium. When the areal recording density exceeds 2 terabits per square inch, the dimensions of the read head will be 20 nm or less. With current tunnel magnetoresistance elements, it is difficult to achieve a sufficient signal-to-noise ratio with such a small read head.

[0003] For example, Patent Documents 1 and 2 disclose read heads that utilize the anomalous Hall effect of ferromagnetic materials. Also, Patent Document 3 discloses a film structure of a current-perpendicular-to-plane giant magnetoresistance element and a spin valve that can be suitably used in read heads.

[0004] FIG. 1A is a conceptual diagram of a conventional read head using the anomalous Hall effect. It shows the relative positions of the read head and magnetic recording medium 11. The ferromagnetic material 10 used in the read head is rectangular and has two pairs of orthogonal terminals attached. Bias currents I+ and I- are applied through one pair of terminals, and voltages V+ and V- are measured through the other pair of terminals. The orientation of magnetization M10 in the ferromagnetic material 10 changes in response to the magnetic field from magnetization M11 stored in the magnetic recording medium 11. When magnetization M10 rotates in a direction perpendicular to these two pairs of terminals, a voltage due to the anomalous Hall effect is generated between the voltage terminals, and the recorded magnetic information is reproduced. The surface of the read head facing the magnetic recording medium is called the air bearing surface (ABS) and is protected by diamond-like carbon (DLC).

[0005] The magnetic recording medium 11 has a magnetic recording pattern arranged in a striped pattern in the in-plane direction and has magnetic recording tracks that store magnetic information by perpendicular magnetization. In the figure, the y direction is the down-track direction, the x direction is the cross-track direction, and the z direction is the perpendicular magnetization direction.

[0006] FIG. 1B is a perspective view illustrating the details of a read head using the first type of anomalous Hall effect. FIG. 1B shows bias current terminals I+ and I- and voltage detection terminals V+ and V-. One of the bias current terminals I+ and I- is a first current terminal, and the other is a second current terminal. One of the voltage detection terminals V+ and V- is a first voltage terminal, and the other is a second voltage terminal. The y direction in FIG. 1B is the voltage direction of the voltage generated between the pair of voltage detection terminals V+ and V-, the x direction is the current direction of the current flowing between the pair of bias current terminals I+ and I-, and the z direction is the perpendicular magnetization direction of the magnetic recording medium 11. A leakage magnetic field H from the magnetic recording medium 11 is applied to the ferromagnetic material 10. The z direction is perpendicular to the air bearing surface and perpendicular to the plane defined by the x and y directions.

[0007] In the first type, the voltage detection terminals V+ and V- correspond to the upper shield 31 and lower shield 33 in FIG. 1D, and the bias current terminals I+ and I- correspond to the side shields 32a and 32b in FIG. 1D.

[0008] Figure 1C is a perspective view illustrating the details of a second-type read head using the anomalous Hall effect. The bias current terminals I+, I- and voltage detection terminals V+, V- are arranged in the opposite direction, unlike in Figure 1B. The y direction in Figure 1C is the current direction of the current flowing between the pair of bias current terminals I+, I-, the x direction is the voltage direction of the voltage generated between the pair of voltage detection terminals V+, V-, and the z direction is the perpendicular magnetization direction of the magnetic recording medium. The z direction is perpendicular to the air bearing surface and perpendicular to the plane defined by the x and y directions.

[0009] In the second type, the bias current terminals I+ and I- are the upper shield 31 and the lower shield 33 in FIG. 1D, and the voltage detection terminals V+ and V- are the side shields 32a and 32b in FIG. 1D.

[0010] Japanese Patent Publication No. 2003-069107 U.S. Patent No. 7,576,948 Japanese Patent No. 7066222

[0011] Nakatani et al., "Study on a lead sensor for HDDs using the anomalous Hall effect," 46th Annual Meeting of the Magnetic Society of Japan, Presentation No. 08aA-9 (2022)

[0012] In a read head using the anomalous Hall effect, the terminals are not actually linear. As shown in FIG. 1D , the terminals are made up of soft magnetic metal thin films surrounding the ferromagnetic body 10, and are called the top shield 31, bottom shield 33, and side shields 32a and 32b, respectively. Further explaining the detailed structure of the read head, an insulator layer 34 is formed between the top shield 31 and the side shields 32a and 32b, and an insulator layer 35 is formed between the bottom shield 33 and the side shields 32a and 32b. A nonmagnetic layer 20a is also located between the ferromagnetic body 10 and the top shield 31. A nonmagnetic layer 20c is also located between the ferromagnetic body 10 and the bottom shield 33. A nonmagnetic layer 20b is also located between the ferromagnetic body 10 and the side shields 32a and 32b, respectively. The side shields 32a and 32b are located on either side of the ferromagnetic body 10 and the nonmagnetic layer 20b, sandwiching the ferromagnetic body 10 and the nonmagnetic layer 20b. These shields 31, 32a, 32b, and 33 have the role of shielding against leakage magnetic fields from the magnetic recording medium and improving the resolution of the read head (see Non-Patent Document 1).

[0013] As a result of extensive research, the inventors have found that the following problem occurs when the reproducing head is operated in the above-described structure.

[0014] The first problem is that the bias current is shunted (bypassed) to the shield that functions as the voltage detection terminal (V+, V-). The shunting of the bias current causes a drop in the output voltage (see Patent Document 2).

[0015] The second problem is that the anomalous Hall voltage leaks to the shield, which functions as the bias current terminal (I+, I-). This leakage causes a drop in the output voltage.

[0016] If the output voltage of the reproducing head is reduced due to these issues, the output required for the reproducing head cannot be obtained sufficiently.

[0017] The present disclosure solves the problems of the conventional technology by providing a read head using the anomalous Hall effect that can suppress a drop in output voltage caused by the bias current being shunted to the voltage detection terminal or the anomalous Hall voltage leaking to the bias current terminal.

[0018] To solve the above problems, the present disclosure provides a structure for suppressing the shunting of the bias voltage to the shield and a structure for suppressing the leakage of the anomalous Hall voltage to the shield, either inside the shield or between the ferromagnetic material and the shield.

[0019] [1] A read head using the anomalous Hall effect according to a first embodiment is shown in, for example, Figures 9A, 9B, 10A, and 10B. The read head according to the first embodiment includes a ferromagnetic body 10 exhibiting the anomalous Hall effect, first and second current terminals (I+, I-) for supplying current to the ferromagnetic body 10, first and second voltage terminals (V+, V-) for detecting a voltage generated in the ferromagnetic body 10, and resistance adjustment layers (34a, 34b, 35a, 35b, 36a, 36b) between the first and second current terminals and the ferromagnetic body, or between the first and second voltage terminals and the ferromagnetic body. The read head according to the first embodiment detects a magnetic field applied in a third direction perpendicular to the air bearing surface when the current direction of the current flowing between the first and second current terminals is defined as a first direction and the voltage direction of the voltage generated between the first and second voltage terminals is defined as a second direction. In the read head according to the first aspect, the resistance adjustment layer includes a high-resistance region and a low-resistance region, and the low-resistance region electrically connects the first current terminal and the second current terminal to the ferromagnetic body, or electrically connects the first voltage terminal and the second voltage terminal to the ferromagnetic body.

[0020] [2] In the reproducing head using the anomalous Hall effect according to the above aspect, the low resistance region may be present in the center of the resistance adjustment layer.

[0021] [3] In the reproducing head using the anomalous Hall effect according to the above aspect, the ferromagnetic material exhibiting the anomalous Hall effect may contain at least two elements selected from the group consisting of cobalt, nickel, iron, holmium, platinum, osmium, bismuth, boron, dysprosium, gadolinium, and terbium.

[0022] [4] In the reproducing head using the anomalous Hall effect according to the above aspect, the ratio of the resistivity of the high resistance region to the resistivity of the low resistance region may be 100 or more.

[0023] [5] In the reproducing head using the anomalous Hall effect according to the above aspect, the resistivity of the high resistance region is 10 ４ μΩ・cm or more 10 ８ It may be μΩ·cm or less.

[0024] [6] In the reproducing head using the anomalous Hall effect according to the above aspect, the resistivity of the low resistance region is 10 ２ μΩ・cm or more 10 ４ It may be μΩ·cm or less.

[0025] [7] In the reproducing head using the anomalous Hall effect according to the above aspect, the high resistance region is made of SiO ｘ , AlO ｘ , MgO, MgTiO, MgAlO, TaO ｘ , HfO ｘ , SiN.

[0026] [8] In the reproducing head using the anomalous Hall effect according to the above aspect, the low resistance region may contain a metal selected from the group consisting of Ru, Ag, Au, Cu, and Ta, or an alloy of these metal elements.

[0027] [9] In the reproducing head using the anomalous Hall effect according to the above aspect, the ferromagnetic material may be an alloy exhibiting an anomalous Hall resistivity of 1 μΩ·cm or more.

[0028]

[10] In the reproducing head using the anomalous Hall effect according to the above aspect, the ferromagnetic material is Co ２ MnAl, Co ２It may include an alloy selected from the group consisting of MnGa and FeSn.

[0029]

[11] In the reproducing head using the anomalous Hall effect according to the above aspect, the first current terminal, the second current terminal, the first voltage terminal, and the second voltage terminal may include a ferromagnetic material with high magnetic permeability.

[0030]

[12] In the reproducing head using the anomalous Hall effect according to the above aspect, the first current terminal, the second current terminal, the first voltage terminal, and the second voltage terminal may contain NiFe.

[0031]

[13] In the reproducing head using the anomalous Hall effect according to the above aspect, the third direction may be perpendicular to the first direction and the second direction.

[0032]

[14] A read head using the anomalous Hall effect according to a second aspect is shown, for example, in Figures 9C and 10C. The read head using the anomalous Hall effect according to the second aspect includes a ferromagnetic body 10 exhibiting the anomalous Hall effect, first and second current terminals (I+, I-) for supplying current to the ferromagnetic body 10, and first and second voltage terminals (V+, V-) for detecting a voltage generated in the ferromagnetic body 10. The read head using the anomalous Hall effect according to the second aspect detects a magnetic field applied in a third direction perpendicular to the air bearing surface when the current direction of the current flowing between the first current terminal and the second current terminal is defined as a first direction and the voltage direction of the voltage generated between the first voltage terminal and the second voltage terminal is defined as a second direction. The first current terminal and the second current terminal have a multilayer structure. The multilayer structure is formed by alternately stacking soft magnetic layers (32a, 32b, 32c) and intermediate layers (37a, 37b) extending along the second direction, and the intermediate layers have a higher resistance than the soft magnetic layers.

[0033]

[15] In the reproducing head using the anomalous Hall effect according to the above aspect, the ratio of the resistivity of the soft magnetic layer to that of the intermediate layer may be 100 or more.

[0034]

[16] In the reproducing head using the anomalous Hall effect according to the above aspect, the soft magnetic layer may contain a ferromagnetic material with high magnetic permeability.

[0035]

[17] In the reproducing head using the anomalous Hall effect according to the above aspect, the soft magnetic layer may contain NiFe.

[0036]

[18] In the reproducing head using the anomalous Hall effect according to the above aspect, the intermediate layer is made of SiO ｘ , AlO ｘ , MgO, MgTiO, MgAlO, TaO ｘ , HfO ｘ , SiN.

[0037]

[19] In the reproducing head using the anomalous Hall effect according to the above aspect, the thickness of the soft magnetic layer may be at least twice the thickness of the intermediate layer.

[0038]

[20] In the reproducing head using the anomalous Hall effect according to the above aspect, the first voltage terminal and the second voltage terminal may include a ferromagnetic material with high magnetic permeability.

[0039]

[21] In the reproducing head using the anomalous Hall effect according to the above aspect, the first voltage terminal and the second voltage terminal may contain NiFe.

[0040]

[22] In the reproducing head using the anomalous Hall effect according to the above aspect, the third direction may be perpendicular to the first direction and the second direction.

[0041]

[23] A magnetic disk drive according to a third aspect includes a magnetic head, a slider disposed facing a rotationally driven recording medium, and a positioning device that supports the slider and positions it relative to the recording medium. The magnetic head has a medium-facing surface (air-bearing surface) facing the recording medium. The magnetic head has a read head using the anomalous Hall effect according to the above aspect near the medium-facing surface to detect a signal magnetic field from the recording medium.

[0042]

[24] A magnetic storage device according to a fourth aspect is shown in, for example, Fig. 1A. The magnetic storage device according to the fourth aspect includes a magnetic recording medium having a magnetic storage pattern arranged in a striped pattern in the in-plane direction and performing magnetic storage by perpendicular magnetization, and a reproducing head facing the magnetic recording medium and reading the magnetic storage pattern. The reproducing head is a reproducing head using the anomalous Hall effect according to the above aspect.

[0043] The read head using the anomalous Hall effect disclosed herein has a structure inside the shield or between the ferromagnetic material and the shield that suppresses the shunting of the bias voltage to the shield and a structure that suppresses the leakage of the anomalous Hall voltage to the shield, thereby providing sufficient output as a read head.

[0044] For example, by using a read head having the structure of the first embodiment shown in FIG. 9A, the second embodiment shown in FIG. 9B, or the third embodiment shown in FIG. 9C, it is possible to prevent the bias current flowing through the ferromagnetic material from being shunted to the shield that functions as the bias current terminals (I+, I-).

[0045] Furthermore, when a read head having the structure of the first embodiment shown in FIG. 10A, the second embodiment shown in FIG. 10B, or the third embodiment shown in FIG. 10C is used, the output voltage generated in the ferromagnetic material by the anomalous Hall effect can be prevented from leaking by the shield that functions as the bias current terminals (I+, I−).

[0046] 1 is a conceptual diagram of a conventional read head using the anomalous Hall effect, showing the positional relationship between a magnetic recording medium and the read head. FIG. 1 is a structural perspective view illustrating the details of a first type of read head. FIG. 2 is a structural perspective view illustrating the details of a second type of read head. FIG. 3 is a view of the read head as seen from the air bearing surface side, showing a specific example of the shape of the terminal. FIG. 4 is a schematic diagram of a read head using the anomalous Hall effect according to the first embodiment. FIG. 5 is a schematic diagram of a read head using the anomalous Hall effect according to the second embodiment. FIG. 6 is a schematic diagram of a read head using the anomalous Hall effect according to the third embodiment. FIG. 7 is a schematic diagram of a read head using the anomalous Hall effect according to the first embodiment. FIG. 8 is a schematic diagram of a read head using the anomalous Hall effect of a conventional structure. FIG. 9 is a diagram showing the relationship between the diameter of the low-resistance pinhole layer and the normalized output voltage in the read head according to the first embodiment. FIG. 10 is a diagram showing the relationship between the resistivity of the high-resistance layer and the normalized output voltage in the read head according to the first embodiment. FIG. 11 is a schematic diagram of a first modified example of the read head using the anomalous Hall effect according to the first embodiment. FIG. 12 is a diagram showing the relationship between the position of the low-resistance pinhole layer and the normalized output voltage in the read head according to the first modified example. FIG. 13 is a diagram explaining a manufacturing process of the read head using the anomalous Hall effect according to the first embodiment. FIG. 1 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 2 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 3 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 4 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 5 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 6 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 7 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 8 is a diagram illustrating a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment.FIG. 1 is a diagram explaining a manufacturing process of a read head using the anomalous Hall effect according to the first embodiment. FIG. 2 is a schematic diagram of a read head using the anomalous Hall effect according to the second embodiment. FIG. 3 is a diagram showing the relationship between the diameter of a low-resistance pinhole layer and normalized output voltage in a read head according to the second embodiment. FIG. 4 is a diagram showing the relationship between the resistivity of a high-resistance layer and normalized output voltage in a read head according to the second embodiment. FIG. 5 is a schematic diagram of a read head using the anomalous Hall effect according to the third embodiment. FIG. 6 is a diagram showing the relationship between the resistivity of a high-resistance layer and normalized output voltage in a read head according to the third embodiment. FIG. 7 is a diagram explaining a manufacturing process of a read head using the anomalous Hall effect according to the third embodiment. FIG. 8 is a diagram explaining a manufacturing process of a read head using the anomalous Hall effect according to the third embodiment. FIG. 9 is a diagram explaining a manufacturing process of a read head using the anomalous Hall effect according to the third embodiment. FIG. 10 is a diagram explaining a structure in a read head using the anomalous Hall effect according to the first embodiment that prevents a bias current flowing through a ferromagnetic material from being shunted to a shield that serves as the bias current terminals (I+, I−). FIG. 10 is a diagram illustrating a structure for preventing a bias current flowing in a ferromagnetic material from being shunted to a shield that serves as the bias current terminals (I+, I-) in a read head using the anomalous Hall effect according to a second embodiment. FIG. 11 is a diagram illustrating a structure for preventing a bias current flowing in a ferromagnetic material from being shunted to a shield that serves as the bias current terminals (I+, I-) in a read head using the anomalous Hall effect according to a third embodiment. FIG. 12 is a diagram illustrating a structure for suppressing a phenomenon in which an output voltage due to the anomalous Hall effect generated in a ferromagnetic material leaks through a shield that serves as the bias current terminals (I+, I-) in a read head using the anomalous Hall effect according to the first embodiment. FIG. 13 is a diagram illustrating a structure for suppressing a phenomenon in which an output voltage due to the anomalous Hall effect generated in a ferromagnetic material leaks through a shield that serves as the bias current terminals (I+, I-) in a read head using the anomalous Hall effect according to the first embodiment.FIG. 10 is a diagram illustrating a structure for suppressing the phenomenon in which the output voltage due to the anomalous Hall effect generated in a ferromagnetic material leaks through a shield that serves as the bias current terminals (I+, I−) in a read head using the anomalous Hall effect according to the first embodiment.

[0047] First, let us explain the technical terms used in this specification. The anomalous Hall effect is a Hall effect specific to magnetic materials. When a current is applied to a magnetic material, the current is bent in a direction perpendicular to both the applied current and the magnetization of the magnetic material. The anomalous Hall effect is known to originate from an intrinsic mechanism due to the electronic structure of the material, and an extrinsic mechanism originating from impurity scattering, etc.

[0048] Next, a specific example of the reproducing head according to this embodiment will be described below with reference to the drawings.

[0049] 2A is a schematic diagram of a read head using the anomalous Hall effect according to a first embodiment, FIG. 2B is a schematic diagram of a read head using the anomalous Hall effect according to a second embodiment, and FIG. 2C is a schematic diagram of a read head using the anomalous Hall effect according to a third embodiment.

[0050] First Embodiment As shown in FIG. 2A , the read head shown in the first embodiment has a laminate of soft magnetic metal thin films surrounding a ferromagnetic body 10. The soft magnetic bodies are called an upper shield 31, a lower shield 33, and a side shield 32, respectively. The detailed structure of the read head is as follows: a high-resistance layer (or insulating layer) 34 is located between the upper shield 31 and the side shield 32; a high-resistance layer (or insulating layer) 35 is located between the lower shield 33 and the side shield 32; a resistance adjustment layer is located between the ferromagnetic body 10 and the upper shield 31; the resistance adjustment layer includes a high-resistance layer 34a corresponding to the high-resistance region and a low-resistance pinhole layer 34b corresponding to the low-resistance region; a resistance adjustment layer is located between the ferromagnetic body 10 and the lower shield 33; the resistance adjustment layer includes a high-resistance layer 35a corresponding to the high-resistance region and a low-resistance pinhole layer 35b corresponding to the low-resistance region; and a nonmagnetic layer 20b is located between the ferromagnetic body 10 and the side shield 32. The side shields 32 are located on the left and right sides of the ferromagnetic body 10 and the nonmagnetic layer 20b, sandwiching the ferromagnetic body 10 and the nonmagnetic layer 20b.

[0051] The read head according to the first embodiment has low-resistance pinhole layers 34b and 35b surrounded by high-resistance layers 34a and 35a between the upper shield 31 and the lower shield 33 and the ferromagnetic material 10. A finite element method simulation was performed to examine the effect of this structure.

[0052] 3A is a diagram showing the configuration of a read head using the anomalous Hall effect according to the first embodiment used in the simulation, and FIG. 3B is a diagram showing the configuration of a read head without a low-resistance pinhole layer used in the simulation as a comparative example.

[0053] As shown in Figures 1B and 1C, the ferromagnetic body 10 has a substantially rectangular parallelepiped shape and is represented by three-dimensional coordinates in the x, y, and z directions. The dimensions of the ferromagnetic body 10 are 9 nm in the x direction, 9 nm in the z direction, and 13 nm in the y direction. The resistivity of the ferromagnetic body 10 is 220 µΩ cm. The material of the ferromagnetic body 10 is, for example, Co. ２ MnAl, Co ２ Examples of suitable materials include an MnGa Heusler alloy, an FeSn alloy, etc. The material of the ferromagnetic body 10 preferably includes an alloy that exhibits an anomalous Hall resistivity of 1 μΩ cm or more, and preferably includes an alloy of an element selected from the group consisting of cobalt, nickel, iron, holmium, platinum, osmium, bismuth, boron, dysprosium, gadolinium, and terbium.

[0054] In the case of a read head structure using the first type of anomalous Hall effect shown in FIG. 1B , the x direction is the current direction (first direction) of the current flowing between the pair of bias current terminals I+ and I-, and the y direction is the voltage direction (second direction) of the voltage generated between the pair of voltage detection terminals V+ and V-. The z direction corresponds to the third direction. Furthermore, in the case of a read head structure using the second type of anomalous Hall effect shown in FIG. 1C , the y direction is the current direction (first direction) of the current flowing between the pair of bias current terminals I+ and I-, and the x direction is the voltage direction (second direction) of the voltage generated between the pair of voltage detection terminals V+ and V-. In this case, the z direction also corresponds to the third direction.

[0055] The resistivity of the top shield 31, bottom shield 33, and side shield 32 is, for example, 20 μΩ·cm, and they may contain, for example, NiFe.

[0056] Low-resistance pinhole layers 34b, 35b are provided above and below the ferromagnetic material 10 and are circular in shape in the zx plane. The low-resistance pinhole layers 34b, 35b are surrounded by high-resistance layers 34a, 35a. The resistivity of the pinhole layers 34b, 35b is, for example, 25 μΩ·cm, and they may contain, for example, Ru. The low-resistance pinhole layers 34b, 35b correspond to the low-resistance regions of the resistance adjustment layer, and the high-resistance layers 34a, 35a correspond to the high-resistance regions of the resistance adjustment layer.

[0057] The high resistance layers (or insulating layers) 34 and 35 and the high resistance layers 34a and 35a corresponding to the high resistance regions of the resistance adjusting layer may be made of the same material. For example, SiO ｘ , AlO ｘ , MgO, MgTiO, MgAl, TaO ｘ , HfO ｘ , SiN may be used for the high resistance layers 34a, 35a.

[0058] The ratio of the resistivity of the high resistance region of the resistance adjustment layer to the resistivity of the low resistance region of the resistance adjustment layer is 100 or more and 10 ６ It is preferable that the ratio is 100 or more and 10 ４ The resistivity of the high resistance region of the resistance adjusting layer is more preferably 10 ４ μΩ・cm or more 10 ８ The resistivity of the low resistance region of the resistance adjusting layer is preferably 10 ２ μΩ・cm or more 10 ４ The material of the low resistance region of the resistance adjusting layer is not limited to Ru, but may be Ag, Au, Cu, Ta, or an alloy thereof.

[0059] 3C shows the dependence of the output voltage of the read head according to the first embodiment on the diameter of the low-resistance pinhole layers 34b, 35b. The output voltage is normalized by the output voltage when no low-resistance pinhole layers are provided (the comparative example shown in FIG. 3B). The read head with the low-resistance pinhole layers 34b, 35b has a significantly increased output voltage compared to the comparative example without the low-resistance pinhole layers 34b, 35b, and this effect is greater as the diameter of the low-resistance pinhole layers 34b, 35b becomes smaller.

[0060] A similar effect can be obtained even when the low resistance pinhole layers 34b and 35b are not circular but have a slit shape having the same dimension as the ferromagnetic body 10 in the y direction.

[0061] 3D shows the relationship between the resistivity of the high-resistance layers 34a and 35a and the output voltage when the diameter of the low-resistance pinhole layer is 2 nm, 4 nm, and 8 nm. In order to obtain a high output voltage, the resistivity of the high-resistance layers 34a and 35a should be approximately 10 ４ μΩ・cm or more 10 ８ It is sufficient if it is μΩ·cm or less.

[0062] The most desirable position for the low resistance pinhole layers 34b and 35b is the center of the ferromagnetic body 10. The results showing this are as follows.

[0063] 4B shows the change in output voltage when the positions of the upper and lower low-resistance pinhole layers 34b and 35b are shifted by L / 2 from the center of the ferromagnetic material 10 as shown in FIG. 4A. The output voltage decreases as the shift amount L increases. This is because the output voltage leaks more due to the side shield 32 as the shift amount L increases.

[0064] 5A to 5M are diagrams illustrating a manufacturing process for a read head using the anomalous Hall effect according to the first embodiment.

[0065] (1) As shown in Fig. 5A, photoresist 38 is formed in a region on the bottom shield 33 where a low-resistance pinhole layer 35b is to be formed. Next, a high-resistance layer 35 is formed by sputtering or atomic layer deposition (ALD) on the bottom shield 33 that is not covered with the photoresist 38. Note that here, the high-resistance layer 35 and the high-resistance layer 35a corresponding to the high-resistance region of the resistance adjustment layer are simultaneously formed using the same material.

[0066] (2) As shown in FIG. 5B, the photoresist 38 is peeled off to expose the region where the low-resistance pinhole layer 35b is to be formed.

[0067] (3) As shown in FIG. 5C, a low-resistance pinhole layer 35b is formed.

[0068] (4) As shown in Fig. 5D, a film equivalent to the low-resistance pinhole layer 35b formed on the high-resistance layer 35 is removed by chemical mechanical polishing or the like. The low-resistance pinhole layer 35b, the high-resistance layer (or insulator layer) 35, and the high-resistance layer 35a corresponding to the high-resistance region of the resistance adjustment layer are planarized.

[0069] (5) As shown in FIG. 5E, a ferromagnetic material 10a is deposited on the high resistance layer 35, the high resistance layer 35a corresponding to the high resistance region of the resistance adjustment layer, and the low resistance pinhole layer 35b.

[0070] (6) As shown in Fig. 5F, a photoresist 39 is formed on the formed ferromagnetic body 10a. Next, a portion of the ferromagnetic body 10a is etched through the photoresist 39 by argon ion milling or the like to form the ferromagnetic body 10.

[0071] (7) As shown in FIG. 5G, a non-magnetic layer 20b such as Ru is formed by ALD or the like, and then a side shield 32 is formed on the high resistance layer (or insulating layer) 35.

[0072] (8) As shown in FIG. 5H, argon ion milling is performed with the incident direction tilted relative to the vertical of the substrate surface to remove the side shield 32 and nonmagnetic layer 20b deposited on the side walls of the photoresist 39.

[0073] (9) As shown in Fig. 5I, the photoresist 39 is trimmed by dry etching using oxygen gas or the like. The width of the photoresist 39 is reduced until it reaches a width corresponding to the region where the low-resistance pinhole layer 34b is to be formed.

[0074] (10) As shown in Fig. 5J, a high-resistance layer (or an insulating layer) 34 is formed on the side shield 32 by ALD or the like. A high-resistance layer 34a is formed on the exposed surface of the ferromagnetic material 10 except for the region where the low-resistance pinhole layer 34b is to be formed.

[0075] (11) As shown in Fig. 5K, the photoresist 39 remaining in Fig. 5I is stripped off. By stripping off the photoresist 39, the region where the low-resistance pinhole layer 34 is to be formed is exposed.

[0076] (12) As shown in FIG. 5L, a low-resistance pinhole layer 34b is formed on the ferromagnetic material 10 in the same manner as in processes (3) and (4), and then planarized by chemical mechanical polishing or the like.

[0077] (13) As shown in FIG. 5M, the upper shield 31 is formed on the low resistance pinhole layer 34b, the high resistance layer 34a, and the high resistance layer (or insulating layer) 34.

[0078] Alternatively, a nanocomposite structure in which metal particles are dispersed in an insulator may be used as the resistance adjustment layer. The nanocomposite structure is located between the ferromagnetic material 10 and the bottom shield 33 and top shield 31. In this case, an increase in output voltage can be obtained, similar to when the resistance adjustment layer has a low-resistance pinhole layer. The nanocomposite structure can be fabricated, for example, by the following manufacturing methods: (1) A method in which a non-solid-solution insulator and a metal are simultaneously deposited on the portions adjacent to the ferromagnetic material 10 above and below, followed by phase separation. (2) A method in which an Al-Cu alloy is deposited on the portions adjacent to the ferromagnetic material 10 above and below, followed by exposure to oxygen or oxygen plasma to preferentially oxidize the Al. (3) A method in which a precursor thin film such as Ag-In-Zn-O is deposited on the portions adjacent to the ferromagnetic material 10 above and below, followed by heat treatment to separate the Mn in the ferromagnetic material 10 and the In in the precursor. ２ O ３ A method of causing an oxidation-reduction reaction between

[0079] The read head according to the first embodiment may have a structure conforming to the structure of the read head using the first type of anomalous Hall effect shown in FIG. 1B, as shown in FIG. 9A. In this case, low-resistance pinhole layers 34b and 35b surrounded by high-resistance layers 34a and 35a are provided between the ferromagnetic material 10 and the top shield 31 and bottom shield 33. When the side shield 32 serves as the bias current terminal (I+, I−), the low-resistance pinhole layers 34b and 35b prevent the bias current (in the first direction) flowing through the ferromagnetic material 10 from being shunted to the top shield 31 and bottom shield 33. As a result, the output voltage measured between the top shield 31 and bottom shield 33 is higher than when the low-resistance pinhole layers 34b and 35b are not provided.

[0080] Alternatively, the read head according to the first embodiment may have a structure similar to that of a read head using the second type of anomalous Hall effect shown in FIG. 1C, as shown in FIG. 10A. In this case, low-resistance pinhole layers 34b and 35b surrounded by high-resistance layers 34a and 35a are provided between the top shield 31 and the bottom shield 33 and the ferromagnetic material 10. When the top shield 31 and the bottom shield 33 are used as bias current terminals (I+, I−), the low-resistance pinhole layers 34b and 35b suppress leakage of output voltage due to the anomalous Hall effect generated in the ferromagnetic material 10 through the top shield 31 and the bottom shield 33. As a result, the output voltage measured between the side shields 32, which corresponds to the voltage generated between the pair of voltage detection terminals V+ and V−, is higher than when the low-resistance pinhole layers 34b and 35b are not provided.

[0081] Second Embodiment Fig. 6A is a diagram showing the configuration of a read head using the anomalous Hall effect according to a second embodiment, which is similar to Fig. 2B.

[0082] As shown in FIG. 2B , the read head according to the second embodiment has a laminate of soft magnetic metal thin films surrounding a ferromagnetic body 10. The soft magnetic bodies are referred to as an upper shield 31, a lower shield 33, and a side shield 32. The detailed structure of the read head includes a high-resistance layer (or insulating layer) 34 between the upper shield 31 and the side shield 32, and a high-resistance layer (or insulating layer) 35 between the lower shield 33 and the side shield 32. A nonmagnetic layer 20a is located between the ferromagnetic body 10 and the upper shield 31. A nonmagnetic layer 20c is located between the ferromagnetic body 10 and the lower shield 33. A high-resistance layer 36a, which corresponds to the high-resistance region, and a low-resistance pinhole layer 36b, which corresponds to the low-resistance region of the resistance adjustment layer, are located between the ferromagnetic body 10 and the side shield 32. The side shields 32 are located on either side of the ferromagnetic body 10 and the nonmagnetic layer 20b, sandwiching the ferromagnetic body 10 and the nonmagnetic layer 20b.

[0083] The read head according to the second embodiment has a low-resistance pinhole layer 36b surrounded by a high-resistance layer 36a between the side shield 32 and the ferromagnetic material 10. A finite element method simulation was performed to examine the effect of this structure.

[0084] Figure 6B shows the pinhole diameter dependence of the output voltage. The output voltage was normalized by the value when no pinhole structure was provided (similar to Figure 3B: comparative example). The read head with the pinhole structure between the ferromagnetic material 10 and the side shield 32 had a higher output voltage than the comparative example without the pinhole structure.

[0085] FIG. 6C shows the dependence of the output voltage on the resistivity of the high-resistance layer 36a around the pinhole. ４ A high output voltage can be obtained at μΩ·cm or higher.

[0086] The read head according to the second embodiment may have a structure using the second type of anomalous Hall effect shown in FIG. 1C , as shown in FIG. 10B . In this case, a low-resistance pinhole layer 36b surrounded by a high-resistance layer 36a is provided between the side shield 32 and the ferromagnetic material 10. The low-resistance pinhole layer 36b suppresses leakage of output voltage due to the anomalous Hall effect generated in the ferromagnetic material 10 through the side shield 32 when the side shield 32 serves as the bias current terminals (I+, I−). As a result, the output voltage measured between the top shield 31 and the bottom shield 33, which corresponds to the voltage generated between the pair of voltage detection terminals V+, V−, is higher than when the low-resistance pinhole layer 36b is not provided.

[0087] Furthermore, the read head of the second embodiment may have a structure conforming to the structure of the read head using the first type of anomalous Hall effect shown in FIG. 1B, as shown in FIG. 9B. In this case, a low-resistance pinhole layer 36b surrounded by a high-resistance layer 36a is provided between the side shield 32 and the ferromagnetic material 10. The low-resistance pinhole layer 36b prevents the bias current (in the first direction) flowing through the ferromagnetic material 10 from being shunted to the side shield 32 when the top shield 31 and bottom shield 33 serve as bias current terminals (I+, I−). As a result, the output voltage measured between the side shields 32 is higher than when the low-resistance pinhole layer 36b is not provided.

[0088] 2C and 7A, a read head according to a third embodiment has a laminate of soft magnetic metal thin films surrounding a ferromagnetic body 10. The soft magnetic bodies are called an upper shield 31, a lower shield 33, and a side shield 32, respectively. The structure of the read head is described in detail below. A high-resistance layer (or insulating layer) 34 is located between the upper shield 31 and the side shield 32, and a high-resistance layer (or insulating layer) 35 is located between the lower shield 33 and the side shield 32. A nonmagnetic layer 20a is located between the ferromagnetic body 10 and the upper shield 31. A nonmagnetic layer 20c is located between the ferromagnetic body 10 and the lower shield 33. A nonmagnetic layer 20b is located between the ferromagnetic body 10 and the side shield 32. The side shields 32 are located on either side of the ferromagnetic body 10 and the nonmagnetic layer 20b, sandwiching the ferromagnetic body 10 and the nonmagnetic layer 20b.

[0089] The side shield 32 according to the third embodiment has a laminated structure of soft magnetic metal layers 32 a, 32 b, and 32 c and high-resistance layers 37 a and 37 b. The soft magnetic metal layers and high-resistance layers are alternately laminated. The soft magnetic metal layers correspond to the soft magnetic layers, and the high-resistance layers correspond to the intermediate layers.

[0090] The thickness of each of the soft magnetic metal layers 32a, 32b, and 32c is preferably 2 to 10 times the thickness of each of the high resistance layers 37a and 37b. The ratio of the resistivity of each of the soft magnetic metal layers 32a, 32b, and 32c to the resistivity of each of the high resistance layers 37a and 37b is preferably 100 to 10. ６ It is preferable that the ratio is 100 or more and 10 ４ More preferably, it is:

[0091] The resistivity of each of the high resistance layers 37a and 37b is 10 ４ μΩ・cm or more 10 ８ The resistivity of each of the soft magnetic metal layers 32a, 32b, and 32c may be 10 ２ μΩ・cm or more 10 ４ The soft magnetic metal layers 32a, 32b, and 32c may contain, for example, NiFe. The high-resistance layers 37a and 37b may contain, for example, SiO. ｘ , AlO ｘ , MgO, MgTiO, MgAl, TaOｘ , HfO ｘ , SiN.

[0092] The read head according to the third embodiment has a layered structure of soft magnetic metal layers 32a, 32b, and 32c and high resistance layers 37a and 37b in the side shield 32. A finite element method simulation was performed to examine the effect of this structure.

[0093] As shown in Figure 7A, the side shield 32 has a structure of soft magnetic metal layer (2.5 nm) / high-resistance layer (1.0 nm) / soft magnetic metal layer (2.5 nm) / high-resistance layer (1.0 nm) / soft magnetic metal layer (2.5 nm) / high-resistance layer (1.0 nm) / soft magnetic metal layer (2.5 nm). Here, the number of high-resistance layers is three, but this is just an example, and the number of high-resistance layers is not limited to three. The soft magnetic metal layers 32a, 32b, and 32c are, for example, NiFe, and the resistivity is assumed to be 20 μΩ·cm. Figure 7B shows the dependence of the output voltage of a read head having such a side shield 32 on the resistivity of the high-resistance layers 37a and 37b. When the resistivity of the high-resistance layers 37a and 37b is approximately 10 ４ At μΩ·cm or more, the output voltage saturates.

[0094] This means that even if the high resistance layers 37a and 37b are not made of an insulator, ４ In this embodiment, the thickness of the high resistance layers 37a and 37b is set to 1.0 nm. ４ The resistivity of μΩ·cm is 0.1 Ω·μm ２ When magnesium oxide of about 1 nm is used as the high resistance layers 37a and 37b, the resistance is approximately 1 Ω·μm ２ An RA value of 0.1 or less can be obtained. It is known that ferromagnetic exchange coupling occurs between two ferromagnetic layers sandwiching magnesium oxide with such a low RA value. This ferromagnetic exchange coupling promotes magnetic stability as a side shield 32, which is advantageous in terms of the properties of the side shield 32.

[0095] 8A to 8E show a manufacturing process of a read head using a side shield 32 having a laminated structure of soft magnetic metal layers 32a, 32b, and 32c and high resistance layers 37a and 37b.

[0096] (1) As shown in Fig. 8A, an insulator layer 35 is formed on the bottom shield 33. Next, soft magnetic metal layers 32a, 32b, and 32c and high-resistance layers 37a and 37b are alternately formed on the insulator layer 35, and an insulator layer 34 is formed thereon.

[0097] (2) As shown in FIG. 8B, a trench is formed through the side shield 32 by ion milling or dry etching.

[0098] (3) As shown in FIG. 8C, a nonmagnetic layer 20c (such as Ru) is deposited on the bottom of the trench using atomic layer deposition (ALD), and a nonmagnetic layer 20b (such as Ru) is deposited on the sidewalls of the trench.

[0099] (4) As shown in FIG. 8D, a layer of ferromagnetic material 10 is deposited in the trench and the surface is planarized.

[0100] (5) As shown in FIG. 8E, after the nonmagnetic layer 20a is formed on the ferromagnetic layer 10 and the soft magnetic metal layer 32a, the top shield 31 is formed.

[0101] The read head according to the third embodiment may have the structure of a read head using the second type of anomalous Hall effect shown in FIG. 1C , as shown in FIG. 10C . In this case, the read head has a side shield 32 with a laminated structure of soft magnetic metal layers 32a, 32b, and 32c and high-resistance layers 37a and 37b. When the side shield 32 serves as the bias current terminals (I+, I−), the side shield 32 with a laminated structure suppresses the phenomenon in which the output voltage due to the anomalous Hall effect generated in the ferromagnetic material 10 leaks through the side shield 32. As a result, the output voltage measured between the top shield 31 and the bottom shield 33, which corresponds to the voltage generated between the pair of voltage detection terminals V+ and V−, is higher than in a case without this laminated structure.

[0102] Alternatively, the read head according to the third embodiment may have a structure conforming to the structure of the read head using the first type of anomalous Hall effect shown in FIG. 1B, as shown in FIG. 9C. In this case, the read head has a stacked structure of soft magnetic metal layers 32a, 32b, and 32c and high-resistance layers 37a and 37b in the side shields 32. The stacked side shields 32 prevent the bias current (in the first direction) flowing through the ferromagnetic material 10 from being shunted to the side shields 32 when the upper shield 31 and the lower shield 33 serve as bias current terminals (I+, I−). As a result, the output voltage measured between the side shields 32 is higher than when this stacked structure is not included.

[0103] In the above embodiments, examples have been shown for each of the cases where there is a resistance adjustment layer between the upper and lower shields and the ferromagnetic material, where there is a resistance adjustment layer between the side shield and the ferromagnetic material, and where the side shield has a laminated structure of a soft magnetic material and a high resistance, but these structures may also be combined.

[0104] The read head using the anomalous Hall effect of the present disclosure is able to suppress the bias current from shunting to the voltage detection terminal and the anomalous Hall voltage from leaking to the bias current terminal, making it difficult for the output voltage to decrease. As a result, the read head of the present disclosure has a large output and is suitable for use in magnetic storage devices.

[0105] 10 Ferromagnetic material 20a, 20b, 20c Non-magnetic layer 31 Top shield 32 Side shield 32a, 32b, 32c, 32d Soft magnetic metal layer 33 Bottom shield 34, 35 Insulator layer 34a, 35a High resistance layer (high resistance region of resistance adjustment layer) 34b, 35b Low resistance pinhole layer (low resistance region of resistance adjustment layer) 37a, 37b Insulator layer (high resistance layer) 38, 39 Photoresist I+, I- Bias current terminals V+, V- Voltage detection terminals

Claims

1. A reproducing head using the anomalous Hall effect, comprising: a ferromagnetic body exhibiting an anomalous Hall effect; first and second current terminals supplying a current to the ferromagnetic body; first and second voltage terminals detecting a voltage generated in the ferromagnetic body; and a resistance adjustment layer between the first and second current terminals and the ferromagnetic body, or between the first and second voltage terminals and the ferromagnetic body, wherein a magnetic field applied in a third direction perpendicular to an air bearing surface can be detected using the anomalous Hall effect when a current direction of a current flowing between the first and second current terminals is defined as a first direction and a voltage direction of a voltage generated between the first and second voltage terminals is defined as a second direction, and the resistance adjustment layer includes a high resistance region and a low resistance region, and the low resistance region electrically connects the first and second current terminals and the ferromagnetic body, or electrically connects the first and second voltage terminals and the ferromagnetic body.

2. The read head using the anomalous Hall effect as recited in claim 1, wherein the low resistance region is in the center of the resistance adjustment layer.

3. The extraordinary Hall effect read head of claim 1, wherein the ferromagnetic material includes at least two of the elements selected from the group consisting of cobalt, nickel, iron, holmium, platinum, osmium, bismuth, boron, dysprosium, gadolinium, and terbium.

4. The reproducing head using the anomalous Hall effect as recited in claim 1, wherein the ratio of resistivity of said high resistance region to said low resistance region is 100 or more.

5. The resistivity of the high resistance region is 10 ４ μΩ・cm or more 10 ８ 5. The reproducing head using the anomalous Hall effect according to claim 4, wherein the resistivity is less than μΩ·cm.

6. The resistivity of the low resistance region is 10 ２ μΩ・cm or more 10 ４ 6. The reproducing head using the anomalous Hall effect according to claim 5, wherein the reproducing resistance is less than μΩ·cm.

7. The high resistance region is made of SiO ｘ , AlO ｘ , MgO, MgTiO, MgAl, TaO ｘ , HfO ｘ 2. The anomalous Hall effect read head of claim 1, comprising an oxide or nitride selected from the group consisting of SiN.

8. The reproducing head using the anomalous Hall effect according to claim 1, wherein the low resistance region includes a metal selected from the group consisting of Ru, Ag, Au, Cu, and Ta, or an alloy of these metal elements.

9. The anomalous Hall effect reproducing head of claim 1, wherein the ferromagnetic material is an alloy exhibiting an anomalous Hall resistivity of 1 μΩ·cm or greater.

10. The ferromagnetic material is Co ２ MnAl,Co ２ 10. The anomalous Hall effect read head of claim 9, comprising an alloy selected from the group consisting of MnGa, FeSn.

11. The extraordinary Hall effect read head of claim 1, wherein said first current terminal, said second current terminal, said first voltage terminal and said second voltage terminal comprise a magnetically soft ferromagnetic material.

12. The extraordinary Hall effect read head of claim 11, wherein the first current terminal, the second current terminal, the first voltage terminal, and the second voltage terminal comprise NiFe.

13. The extraordinary Hall effect read head of claim 1, wherein the third direction is perpendicular to the first direction and the second direction.

14. A reproducing head using the anomalous Hall effect, comprising: a ferromagnetic body exhibiting an anomalous Hall effect; first and second current terminals for supplying a current to the ferromagnetic body; and first and second voltage terminals for detecting a voltage generated in the ferromagnetic body, wherein a magnetic field applied in a third direction perpendicular to an air bearing surface can be detected using the anomalous Hall effect when a first direction is a flow direction of a current flowing between the first current terminal and the second current terminal and a second direction is a generation direction of a voltage generated between the first and second voltage terminals, wherein the first and second current terminals have a multi-layer structure, and the multi-layer structure is formed by alternately stacking soft magnetic layers and intermediate layers extending along the second direction, and the intermediate layers have a higher resistance than the soft magnetic layers.

15. The anomalous Hall effect read head of claim 14, wherein the ratio of resistivities of said soft magnetic layer and said intermediate layer is 100 or greater.

16. The extraordinary Hall effect read head of claim 14, wherein the soft magnetic layer comprises a magnetically soft ferromagnetic material.

17. The extraordinary Hall effect read head of claim 16, wherein the soft magnetic layer comprises NiFe.

18. The intermediate layer is made of SiO ｘ , AlO ｘ , MgO, MgTiO, MgAlO, TaO ｘ , HfO ｘ 15. The anomalous Hall effect read head of claim 14, comprising an oxide or nitride selected from the group consisting of SiN.

19. The anomalous Hall effect read head of claim 14, wherein the thickness of the soft magnetic layer is at least twice the thickness of the intermediate layer.

20. The extraordinary Hall effect read head of claim 14, wherein the first voltage terminal and the second voltage terminal comprise a magnetically soft ferromagnetic material.

21. The extraordinary Hall effect read head of claim 20, wherein the first voltage terminal and the second voltage terminal comprise NiFe.

22. The extraordinary Hall effect read head of claim 14, wherein the third direction is perpendicular to the first direction and the second direction.

23. A magnetic disk drive comprising: a magnetic head; a slider arranged to face a rotationally driven recording medium; and a positioning device that supports the slider and positions it relative to the recording medium, wherein the magnetic head has a medium facing surface that faces the recording medium, and the magnetic head comprises, in the vicinity of the medium facing surface, a reproducing head using the anomalous Hall effect described in any one of claims 1 to 22.

24. A magnetic storage device comprising: a magnetic recording medium having a magnetic memory pattern arranged in stripes in the in-plane direction and storing magnetic information by perpendicular magnetization; and a reproducing head facing the magnetic recording medium and reading out the magnetic memory pattern, the reproducing head being a reproducing head using the anomalous Hall effect as described in any one of claims 1 to 22.

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