A self-biased spin valve device

Abstract

The application discloses a self-biased spin valve device and belongs to the field of magnetoelectric materials. The self-biased spin valve device comprises a base and a substrate, and the base comprises a covering layer, a first pinning layer, a first pinned layer, a first isolation layer, a free layer, a second isolation layer, a second pinned layer, a second pinning layer and a buffer layer. The self-biased spin valve device is prepared by adjusting the type and thickness of the spin valve buffer layer, so as to achieve the same optimization effect as the optimization of the isolation layer, to realize self-bias, and to reduce the preparation difficulty of the spin valve device. The magnetoresistance curve of the self-biased spin valve device has the advantages of linear response to an external magnetic field, low saturation field, high magnetic field sensitivity and the like. The free layer is partially biased to the same side of the magnetic field, so that the requirement of the self-biased spin valve device is met.

Description

Technical Field

[0001] This invention relates to the field of magnetoelectric materials, and more specifically, to a self-biased spin valve device. Background Technology

[0002] Spin valve magnetic sensors are devices that convert electrical signals into electrical signals by changing the magnetic properties of GMR magnetic sensing elements. They possess advantages such as linear response to external magnetic fields due to magnetoresistivity, low saturation fields, and high magnetic field sensitivity. The basic spin valve structure consists of a "ferromagnetic free layer / non-magnetic isolation layer / ferromagnetic pinning layer / antiferromagnetic pinning layer," based on the giant magnetoresistance effect (GMR). GMR refers to the phenomenon where the resistivity of a magnetic multilayer film changes dramatically under an applied magnetic field compared to when no external magnetic field is applied. Therefore, magnetic field detection and sensor fabrication can be achieved by detecting changes in resistance. Tactile perception can be achieved by using spin valve devices to sense changes in the magnetic field caused by external forces, thus fabricating magnetic tactile sensors. These tactile sensors generally include a magnetic sensing layer, a magnetic field propagation medium layer, a magnetic sensing element, and a substrate. As a type of magnetic sensing element in magnetic tactile sensors, the spin valve sensor needs to operate continuously and repeatedly within a given magnetic field range of the magnetic film. Therefore, it is essential to ensure that the free layer portion of the spin valve curve is biased towards the same side of the magnetic field. In addition, in order for the sensor to quickly return to its initial state, the spin valve device must also meet requirements such as low hysteresis and a linear response to the external magnetic field.

[0003] In spin valve structures, to achieve rapid biasing and low coercivity in the free layer, the adjacent isolation layer is typically optimized. However, optimizing the isolation layer presents certain challenges, including the need to precisely control its thickness to achieve high GMR values, which places high demands on the manufacturing process. Chinese invention patent CN103605088A discloses a 90-degree self-biased spin valve sensing unit. This unit enables the magnetic moments of the free layer and pinned layer to be oriented at a 90-degree angle in the absence of an external magnetic field, reducing the manufacturing difficulty of the spin valve sensing unit. However, this patent alters the structure of the free layer, which may change the performance of the spin valve. Furthermore, modifying the free layer structure is currently quite difficult. Therefore, whether the same optimization effect can be achieved by adjusting other layers based on the structure of the spin valve itself to achieve self-biasing and thus reduce the fabrication difficulty of spin valve devices is of great significance to the development of magnetoelectric materials. Summary of the Invention

[0004] The problem to be solved by this invention is how to regulate the layers other than the isolation layer so that the free layer of the spin valve has a self-biasing effect.

[0005] To address the aforementioned problems, the present invention provides a self-biased spin valve device, which includes a base and a substrate. The base includes a capping layer, a first pinning layer, a first pinned layer, a first isolation layer, a free layer, a second isolation layer, a second pinned layer, a second pinning layer, and a buffer layer stacked sequentially. The buffer layer is composed of a first metal layer and a second metal layer that are in close contact with each other, with the first metal layer in close contact with the second pinning layer. The substrate is in close contact with the buffer layer.

[0006] The self-biased spin valve device provided by the present invention achieves the effect of self-biasing of the free layer by adjusting the buffer layer.

[0007] Preferably, the first metal layer is selected from platinum, tantalum, and copper; the second metal layer is selected from platinum, tantalum, and copper. The selected metal buffer layer material can effectively reduce interface growth roughness, affect the lattice texture of each layer of the spin valve film, reduce lattice mismatch problems during multilayer film growth, and improve the crystal quality and magnetic properties of the magnetic layer. The self-biasing state of the device can be changed by adjusting the type or parameters of the buffer layer to meet different application requirements.

[0008] Furthermore, the material of the first pinning layer is selected from any one of manganese-iron alloy, manganese-nickel alloy, manganese-platinum alloy, and manganese-iridium alloy; the material of the second pinning layer is selected from any one of manganese-iron alloy, manganese-nickel alloy, manganese-platinum alloy, and manganese-iridium alloy. The pinning layers serve to pin the magnetic moment of the pinned layer, causing the relative magnetization orientation of the pinned layer and the free layer to change with the magnetic field, resulting in variations in the device's resistance. The selected materials have the characteristics of small characteristic thickness, good corrosion resistance, and high resistivity, which can reduce the shunting effect caused by the thickness of the pinning layer to a certain extent.

[0009] Preferably, the thickness of the first pinning layer is 0–20 nm; the thickness of the second pinning layer is 0–20 nm.

[0010] Furthermore, the free layer comprises a first ferromagnetic layer, a second ferromagnetic layer, and a third ferromagnetic layer. The first ferromagnetic layer is in close contact with the first isolation layer. The free layer is a three-layer composite structure. The selected second ferromagnetic layer has low coercivity and low saturation field, so a small external magnetic field can magnetize and flip it. To prevent the diffusion effect caused by the large lattice matching between the second ferromagnetic layer material and the first isolation layer, a relatively thin first ferromagnetic layer is placed between the two layers, which can effectively prevent diffusion and improve the spin-correlated scattering effect.

[0011] Preferably, the material of the first ferromagnetic layer is selected from any one of iron, cobalt, and nickel, or any one or more alloys of iron / cobalt / nickel; the material of the second ferromagnetic layer is selected from any one of iron, cobalt, and nickel, or any one or more alloys of iron / cobalt / nickel; and the material of the third ferromagnetic layer is selected from any one of iron, cobalt, and nickel, or any one or more alloys of iron / cobalt / nickel.

[0012] Preferably, the thickness of the first ferromagnetic layer is less than 10 nm; the thickness of the second ferromagnetic layer is less than 10 nm; and the thickness of the third ferromagnetic layer is less than 10 nm.

[0013] Furthermore, both the first pinned layer and the second pinned layer are made of ferromagnetic materials. The selected pinned layer materials exhibit high coercivity and strong exchange bias with the pinned layers, effectively pinning the magnetization direction.

[0014] Furthermore, the first isolation layer is made of copper; the second isolation layer is made of copper.

[0015] Preferably, the thickness of the first isolation layer is less than 10 nm; the thickness of the second isolation layer is less than 10 nm. The isolation layer directly affects the spin valve performance, as it can reduce the ferromagnetic coupling between the free layer and the pinned layer, and improve the spin scattering effect at the interface between the magnetic and non-magnetic layers.

[0016] The beneficial effects of this invention are as follows: The self-biased spin valve device proposed in this invention refers to the biasing of the free layer. Specifically, as the external magnetic field changes, the curve of the free layer portion of the spin valve device is always on the same side of the magnetic field. This facilitates the device's rapid recovery to its initial state for application in devices such as magnetic tactile sensors. This invention provides a self-biased spin valve device that achieves self-biasing of the free layer without requiring high-level processing techniques or additional biasing structures. The magnetoresistance curve of the free layer is biased to the same side of the magnetic field, providing a technical basis for the fabrication of certain specific sensor devices and reducing the difficulty of device fabrication and control. By adjusting the type and thickness of the spin valve buffer layer, the same optimization effect as the optimized isolation layer can be achieved to realize self-biasing, thereby reducing the fabrication difficulty of the spin valve device. The buffer layer is composed of the aforementioned first metal layer / second metal layer multilayer film structure. The self-biased spin valve device of this invention exhibits linear response to the external magnetic field, low saturation field, and high magnetic field sensitivity. The free layer portion is biased to the same side of the magnetic field, meeting the requirements for a self-biased spin valve device. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the self-biased spin valve device in a specific embodiment of the present invention;

[0018] Figure 2The magnetoresistive curve of the self-biased spin valve device prepared according to the control method of the present invention is shown in a specific embodiment of the present invention.

[0019] Figure 3 The image shows the magnetoresistance curve of the free layer of a self-biased spin valve device prepared according to the control method of the present invention in a specific embodiment of the present invention.

[0020] Explanation of markings in the diagram

[0021] 1-Capping layer; 2-First pinning layer; 3-First pinned layer; 4-First isolation layer; 5-Free layer; 51-First ferromagnetic layer; 52-Second ferromagnetic layer; 53-Third ferromagnetic layer; 6-Second isolation layer; 7-Second pinned layer; 8-Second pinning layer; 9-Buffer layer; 91-First metal layer; 92-Second metal layer; 10-Substrate. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0023] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] In the description of the specific embodiments of the present invention, it should be noted that the terms "left", "right", "inner", "outer", "front", "rear", "head", "tail", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of the invention is usually placed in during use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0025] As described in the background section, in a spin valve, to enable the free layer 5 to generate rapid bias and a low coercive field, the adjacent isolation layer is generally optimized. However, optimizing the isolation layer presents certain contradictions, including the need to precisely control the thickness of the isolation layer to achieve a high GMR value, which places high demands on the manufacturing process. Therefore, developing a self-biasing spin valve device that can regulate other layers while achieving the same optimization effect as regulating the isolation layer is of great significance for magnetoelectric functional material products such as tactile sensors.

[0026] See Figure 1 The present invention provides a specific embodiment of a self-biased device, comprising a base and a substrate, wherein the base comprises, in sequence:

[0027] The structure comprises a capping layer 1, a first pinning layer 2, a first pinned layer 3, a first isolation layer 4, a free layer 5, a second isolation layer 6, a second pinned layer 7, a second pinning layer 8, and a buffer layer 9, with the buffer layer 9 located above the substrate.

[0028] In the self-biased spin valve device provided in this embodiment, the material for preparing the first pinning layer 2 is selected from any one of manganese-iron alloy, manganese-nickel alloy, manganese-platinum alloy, and manganese-iridium alloy, and the thickness of the first pinning layer 2 is 0-20 nm.

[0029] In the self-biased spin valve device provided in this embodiment, the material for preparing the second pinning layer 8 is selected from any one of manganese-iron alloy, manganese-nickel alloy, manganese-platinum alloy, and manganese-iridium alloy, and the thickness of the second pinning layer 8 is 0-20 nm.

[0030] In the self-biased spin valve device provided in this embodiment, the first pinned layer 3 is made of ferromagnetic material, which includes, but is not limited to, iron, cobalt, nickel and their alloys.

[0031] In the self-biased spin valve device provided in this embodiment, the second pinned layer 7 is made of ferromagnetic material, which includes, but is not limited to, iron, copper-nickel and their alloys.

[0032] In the self-biased spin valve device provided in this embodiment, the first isolation layer 4 is made of copper metal.

[0033] In the self-biased spin valve device provided in this embodiment, the second isolation layer 6 is made of copper metal.

[0034] In the self-biased spin valve device provided in this embodiment, the free layer 5 is a multi-layer structure, including a first ferromagnetic layer 51, a second ferromagnetic layer 52 and a third ferromagnetic layer 53.

[0035] In the self-biased spin valve device provided in this embodiment, the first ferromagnetic layer 51 is made of iron, cobalt, nickel or any one or more alloys of iron / cobalt / nickel, and the thickness of the first ferromagnetic layer 51 is 0 to 10 nm.

[0036] In the self-biased spin valve device provided in this embodiment, the second ferromagnetic layer 52 is made of iron, cobalt, nickel or any one or more alloys of iron / cobalt / nickel, and the thickness of the second ferromagnetic layer 52 is 0-10 nm.

[0037] In the self-biased spin valve device provided in this embodiment, the third ferromagnetic layer 53 is made of iron, cobalt, nickel or any one or more alloys of iron / cobalt / nickel, and the thickness of the third ferromagnetic layer 53 is 0-10 nm.

[0038] In the self-biased spin valve device provided in this embodiment, the buffer layer 9 is composed of a first metal layer 91 and a second metal layer 92 that are in close contact with each other, and the first metal layer 91 is in close contact with the second pinning layer 8.

[0039] In the self-biased spin valve device provided in this embodiment, the first metal layer 91 is made of any one of platinum, tantalum, and copper.

[0040] In the self-biased spin valve device provided in this embodiment, the second metal layer 92 is made of any one of platinum, tantalum, and copper.

[0041] Example 1

[0042] Combination Figure 1 In this embodiment, a self-biased spin valve device was deposited using a DC magnetron sputtering system under an external magnetic field H (50–300 Oe): Si substrate / Ta / Pt / IrMn (10 nm) / FeCo (5 nm) / Cu (3 nm) / FeCo (1 nm) / FeNi (6 nm) / FeCo (1 nm) / Cu (3 nm) / FeCo (5 nm) / IrMn (10 nm) / Ta (4 nm). After deposition, the magnetoresistance curve was measured under a varying external magnetic field using a four-probe method.

[0043] The magnetoresistive curve of the aforementioned self-biased spin valve device is as follows: Figure 2 As shown, the curves of the five free layers of the device are as follows: Figure 3 As shown in the figure above, it can be seen that the magnetoresistive curve of the fabricated device exhibits linear response to the external magnetic field, has advantages such as low saturation field and high magnetic field sensitivity, and the five free layers are biased to the same side of the magnetic field, which meets the requirements for self-biased spin valve devices.

[0044] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A self-biased spin valve device, characterized in that, Includes a base and a substrate, the base comprising, from top to bottom, a series of components... The stacked layers include a cover layer (1), a first pinning layer (2), a first pinned layer (3), a first isolation layer (4), a free layer (5), a second isolation layer (6), a second pinned layer (7), a second pinning layer (8), and a buffer layer (9). The buffer layer (9) is composed of a first metal layer (91) and a second metal layer (92) that are in close contact with each other. The first metal layer (91) is in close contact with the lower surface of the second pinning layer (8). The lower surface of the second metal layer (92) is in contact with the substrate. The first metal layer (91) is made of tantalum, and the second metal layer (92) is made of platinum. The material of the first pinning layer (2) is selected from any one of manganese-iron alloy, manganese-nickel alloy, manganese-platinum alloy, and manganese-iridium alloy. The material of the second pinning layer (8) is selected from any one of manganese-iron alloy, manganese-nickel alloy, manganese-platinum alloy, and manganese-iridium alloy.

2. The self-biased spin valve device as described in claim 1, characterized in that, The thickness of the first pinning layer (2) is less than 20 nm, and the thickness of the second pinning layer (8) is less than 20 nm.

3. The self-biased spin valve device as described in claim 1, characterized in that, The free layer (5) includes a first ferromagnetic layer (51), a second ferromagnetic layer (52) and a third ferromagnetic layer (53) arranged sequentially from top to bottom, with the first ferromagnetic layer (51) closely attached to the lower surface of the first isolation layer (4).

4. The self-biased spin valve device as described in claim 3, characterized in that, The material of the first ferromagnetic layer (51) is selected from any one of iron, cobalt, and nickel, or any one or more alloys of iron / cobalt / nickel; the material of the second ferromagnetic layer (52) is selected from any one of iron, cobalt, and nickel, or any one or more alloys of iron / cobalt / nickel; the material of the third ferromagnetic layer (53) is selected from any one of iron, cobalt, and nickel, or any one or more alloys of iron / cobalt / nickel.

5. The self-biased spin valve device as described in claim 3, characterized in that, The thickness of the first ferromagnetic layer (51) is less than 10 nm, the thickness of the second ferromagnetic layer (52) is less than 10 nm, and the thickness of the third ferromagnetic layer (53) is less than 10 nm.

6. The self-biased spin valve device as described in claim 1, characterized in that, The first pinned layer (3) is made of ferromagnetic material, and the second pinned layer (7) is made of ferromagnetic material.

7. The self-biased spin valve device as described in claim 1, characterized in that, The first isolation layer (4) is made of copper, and the second isolation layer (6) is made of copper.

8. The self-biased spin valve device as described in claim 7, characterized in that, The thickness of the first isolation layer (4) is less than 10 nm, and the thickness of the second isolation layer (6) is less than 10 nm.

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