Magnetic thin film, method for manufacturing the same, and magnetic tunnel junction device

Abstract

The present disclosure provides a magnetic thin film and a preparation method thereof, and a magnetic tunnel junction device, the thin film comprising: a substrate; a smoothing layer disposed on the substrate; a cobalt-based ferromagnetic layer disposed on the smoothing layer, having a body-centered cubic structure for lattice matching with the smoothing layer; a manganese-based anti-ferromagnetic layer disposed on the cobalt-based ferromagnetic layer for inducing perpendicular magnetic anisotropy of the cobalt-based ferromagnetic layer; and a capping layer disposed on the manganese-based anti-ferromagnetic layer for protecting the magnetic thin film.

Description

Technical Field

[0001] This disclosure relates to the field of spintronics, and more particularly to a magnetic thin film and its preparation method, and a magnetic tunnel junction device. Background Technology

[0002] With the continuous development of modern computer science and the advent of the information age, the storage of massive amounts of data has become a necessity, placing higher demands on the storage density, read / write speed, and stability of magnetic storage devices. The current mainstream magnetic storage chip's basic storage structure is the magnetic tunnel junction diode (MTJ), mainly composed of a free layer, a reference layer, and an intermediate barrier layer. Information can be stored by changing the magnetization state between the free layer and the reference layer. Early MTJs had the magnetic moments of the free layer and reference layer aligned in-plane; however, the presence of stray fields limited further miniaturization of MTJ devices.

[0003] Traditional cobalt-based magnetic thin films mainly induce perpendicular magnetic anisotropy through the action of heavy metal layers or oxide layers. However, these methods have drawbacks such as small controllable thickness of magnetic thin films, low perpendicular magnetic anisotropy performance, and harsh preparation conditions, which limit their practical application in spintronic devices. Summary of the Invention

[0004] To address the aforementioned technical problems, this disclosure provides a magnetic thin film, a method for preparing the same, and a magnetic tunnel junction device, aiming to at least partially solve the above-mentioned technical problems.

[0005] To solve the above-mentioned technical problems, the technical solution disclosed herein is as follows:

[0006] A magnetic thin film, comprising:

[0007] substrate;

[0008] A smoothing layer is disposed on the aforementioned substrate;

[0009] A cobalt-based ferromagnetic layer, disposed on the smoothing layer, has a body-centered cubic structure and is used to match the lattice of the smoothing layer.

[0010] A manganese-based antiferromagnetic layer is disposed on the cobalt-based ferromagnetic layer to induce the vertical magnetic anisotropy of the cobalt-based ferromagnetic layer.

[0011] A capping layer is disposed on the aforementioned manganese-based antiferromagnetic layer to protect the magnetic thin film.

[0012] In one embodiment, the material of the cobalt-based ferromagnetic layer includes any one of the following: metallic cobalt, cobalt alloy, wherein the cobalt alloy includes at least one of the following: cobalt-iron alloy, cobalt-manganese alloy.

[0013] In one embodiment, the thickness of the cobalt-based ferromagnetic layer ranges from 5 to 200 nm.

[0014] In one embodiment, the material of the manganese-based antiferromagnetic layer includes metallic manganese, and the thickness of the manganese-based antiferromagnetic layer includes 1 to 8 nm.

[0015] In one embodiment, the material of the smoothing layer includes any one of the following: GaAs, Si, MgO, Cr, Fe, Co2MnSi, and the thickness of the smoothing layer includes 5 to 200 nm.

[0016] In one embodiment, the substrate material includes any one of the following: GaAs, Si, MgO.

[0017] In one embodiment, the material of the capping layer includes any one of the following: Pt, Ta, Al, Pd, and the thickness of the capping layer includes 1 to 3 nm.

[0018] Another aspect of this disclosure provides a method for preparing a magnetic thin film, the method comprising:

[0019] A smooth layer is grown on the substrate at a first preset temperature;

[0020] A cobalt-based ferromagnetic layer is grown on the smooth layer at a second preset temperature;

[0021] At a third preset temperature, a manganese-based antiferromagnetic layer is grown on the cobalt-based ferromagnetic layer described above;

[0022] At the aforementioned third preset temperature, a capping layer is grown on the aforementioned manganese-based antiferromagnetic layer to obtain a magnetic thin film.

[0023] In another embodiment, the first preset temperature includes 550–570°C;

[0024] The aforementioned second preset temperature includes: 140~160℃;

[0025] The aforementioned third preset temperature includes 60–80℃.

[0026] Another aspect of this disclosure provides a magnetic tunnel junction device that employs the magnetic thin film in the above embodiments or a magnetic thin film prepared by the above preparation method.

[0027] Based on the above technical solutions, it can be seen that the magnetic thin film and its preparation method, as well as the magnetic tunnel junction device provided in this disclosure, have at least one of the following beneficial effects:

[0028] (1) The present invention prepares a magnetic thin film with perpendicular magnetic anisotropy. The manganese metal in the manganese antiferromagnetic layer induces the cobalt-based metal thin film to generate a large perpendicular magnetic anisotropy. The coercivity and perpendicular magnetic anisotropy of the cobalt-based ferromagnetic layer can be adjusted by changing the thickness of the manganese layer. A capping layer can be deposited on the surface of the manganese antiferromagnetic layer to protect the magnetic thin film from damage.

[0029] (2) The method for preparing magnetic thin film materials provided in this disclosure has the advantages of simple preparation method and low cost, and is very suitable for the preparation of high-performance vertical MTJ devices. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the magnetic thin film material in the embodiments of this disclosure;

[0031] Figure 2 This is a flowchart of the method for preparing magnetic thin film materials in the embodiments of this disclosure;

[0032] Figure 3 This is a hysteresis loop diagram of the magnetic multilayer thin film in Embodiment 1 of this disclosure;

[0033] Figure 4 These are anomalous Hall curves of the magnetic films prepared using Co, CoFe, and Co3Mn films as cobalt-based ferromagnetic layers in Examples 1 to 3 of this disclosure;

[0034] Figure 5 Anomalous Hall curves of magnetic thin films prepared with different manganese-based antiferromagnetic layer thicknesses in Examples 1 and 4 to 6 of this disclosure.

[0035] [Explanation of Labels in the Attached Images]

[0036] 101-Substrate; 102-Smoothing layer; 103-Cobalt-based ferromagnetic layer; 104-Radium-based antiferromagnetic layer; 105-Capping layer. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0038] Because the magnetic moments of the free and reference layers in early MTJs were aligned in-plane, the presence of stray fields limited further miniaturization of MTJ devices. Using materials with perpendicular magnetic anisotropy can address this challenge to some extent, thereby significantly increasing information storage density. Furthermore, spintronic devices based on perpendicular magnetic anisotropy materials also offer advantages such as low power consumption and high stability.

[0039] Currently, the sources of perpendicular magnetic anisotropy (MTJ) are mainly divided into intrinsic perpendicular magnetic crystal anisotropy and perpendicular magnetic anisotropy induced by surface / interface effects. Interface-induced perpendicular magnetic anisotropy generally originates from two sources: one is primarily based on ferromagnetic / nonmagnetic heavy metal structures, typically caused by the hybridization of the 5d orbitals of heavy metals such as Pt, Pd, and Au with the 3d orbitals of transition metals; the other originates from the interface of ferromagnetic metals / oxides, such as Ta / CoFeB / MgO multilayer films. It is worth noting that the perpendicularly easily magnetized CoFeB / MgO structure is one of the most commonly used material systems in current perpendicular magnetic turbulence (MTJ) research.

[0040] Cobalt magnetic films and cobalt-based multi-element magnetic films possess high spin polarization, high Curie temperature, and rich magnetic properties, making them widely studied spintronic materials. Generally, perpendicular magnetic anisotropy is induced through heavy metal or oxide layers. However, in traditional cobalt-based magnetic films, perpendicular magnetic anisotropy is primarily induced through heavy metal or oxide layers. These methods suffer from drawbacks such as small controllable film thickness, low perpendicular magnetic anisotropy performance, and stringent fabrication conditions, limiting their practical application in spintronic devices.

[0041] This disclosure demonstrates that epitaxial growth of a manganese-based antiferromagnetic layer on a monolayer cobalt film and a cobalt-based binary alloy CoFe,Co3Mn can induce significant perpendicular magnetic anisotropy in the cobalt-based film at room temperature. Furthermore, the coercive field strength and the magnitude of magnetic anisotropy can be altered with the thickness of the manganese-based antiferromagnetic layer. The physical principle of this magnetic film is primarily based on the pinning effect of antiferromagnetism. The pinning effect of the manganese layer can induce and control the perpendicular magnetic anisotropy of the cobalt monolayer and cobalt-based alloy films, which is entirely different from the physical mechanism of perpendicular magnetic anisotropy induced by oxides or heavy metal interfaces in previous studies. This structure holds promise for applications in high-performance perpendicular MTJs and related magnetic memory devices. Therefore, this disclosure provides a magnetic film, its fabrication method, and a magnetic tunnel junction device.

[0042] Figure 1 This is a schematic diagram of the structure of the magnetic thin film material in the embodiments of this disclosure.

[0043] like Figure 1 As shown, this disclosure provides a magnetic thin film, which includes: a substrate 101; a smoothing layer 102 disposed on the substrate 101; a cobalt-based ferromagnetic layer 103 disposed on the smoothing layer 102, the cobalt-based ferromagnetic layer 103 having a body-centered cubic structure for lattice matching with the smoothing layer 102; a manganese-based antiferromagnetic layer 104 disposed on the cobalt-based ferromagnetic layer 103 for inducing perpendicular magnetic anisotropy of the cobalt-based ferromagnetic layer 103; and a capping layer 105 disposed on the manganese-based antiferromagnetic layer 104 for protecting the magnetic thin film.

[0044] Through the embodiments of this disclosure, a manganese-based antiferromagnetic layer is deposited on the surface of a cobalt-based ferromagnetic layer. The manganese antiferromagnetic layer induces a large perpendicular magnetic anisotropy in the cobalt-based ferromagnetic layer. By changing the thickness of the manganese layer, the coercivity of the ferromagnetic layer and the magnitude of its perpendicular magnetic anisotropy can be adjusted, thereby obtaining a magnetically anisotropic material with better performance. By depositing a capping layer on the surface of the manganese antiferromagnetic layer, the magnetic film can be protected from damage.

[0045] According to embodiments of this disclosure, the material of substrate 101 includes any one of the following: GaAs, Si, MgO.

[0046] According to embodiments of this disclosure, the material of the smoothing layer 102 includes any one of the following: GaAs, Si, MgO, Cr, Fe, Co2MnSi, and the thickness of the smoothing layer 102 includes 5 to 200 nm.

[0047] According to embodiments of this disclosure, the material of the cobalt-based ferromagnetic layer 103 includes any one of the following: metallic cobalt, cobalt alloy, wherein the cobalt alloy includes at least one of the following: cobalt-iron alloy, cobalt-manganese alloy.

[0048] According to embodiments of this disclosure, the thickness of the cobalt-based ferromagnetic layer 103 includes 5 to 200 nm, and can be selected as 5, 10, 50, 100, 150, 200 nm, etc.

[0049] According to embodiments of this disclosure, the material of the manganese-based antiferromagnetic layer 104 includes metallic manganese, and the thickness of the manganese-based antiferromagnetic layer includes 1 to 8 nm, which can be selected as 1, 2, 3, 4, 5, 6, 7, 8 nm, etc.

[0050] Through the embodiments of this disclosure, manganese metal in a manganese-based antiferromagnetic layer induces a cobalt-based metal thin film to generate a large perpendicular magnetic anisotropy. The coercivity of the ferromagnetic layer and the magnitude of its perpendicular magnetic anisotropy are adjusted by changing the thickness of the manganese-based antiferromagnetic layer.

[0051] According to embodiments of this disclosure, the material of the capping layer 105 includes any one of the following: Pt, Ta, Al, Pd, and the thickness of the capping layer includes 1 to 3 nm.

[0052] Through the embodiments of this disclosure, a capping layer is deposited on the surface of a manganese-based antiferromagnetic layer to protect the magnetic film from damage and oxidation.

[0053] Figure 2 This is a flowchart of the method for preparing magnetic thin film materials in the embodiments of this disclosure.

[0054] like Figure 2 As shown, the method for preparing magnetic thin film materials includes steps S201 to S204.

[0055] In step S201, a smooth layer is grown on the substrate at a first preset temperature.

[0056] According to an embodiment of this disclosure, in step S201, the first preset temperature includes 550 to 570°C, wherein the first preset temperature can be selected from 550, 555, 560, 565, 570°C, etc.

[0057] According to embodiments of this disclosure, GaAs(001) is selected as the substrate material, and a GaAs smoothing layer is deposited on the surface of the GaAs(001) substrate, which can make the interface smoother.

[0058] In step S202, a cobalt-based ferromagnetic layer is grown on the smooth layer at a second preset temperature.

[0059] According to an embodiment of this disclosure, in step S202, the second preset temperature includes 140 to 160°C, wherein the second preset temperature can be selected from 140, 145, 150, 155, 160°C, etc.

[0060] In step S203, a manganese-based antiferromagnetic layer is grown on the cobalt-based ferromagnetic layer at a third preset temperature.

[0061] According to an embodiment of this disclosure, in step S203, the third preset temperature includes 60 to 80°C, wherein the third preset temperature can be selected from 60, 65, 70, 75, 80°C, etc.

[0062] Through the embodiments of this disclosure, a manganese antiferromagnetic layer is deposited on the surface of a cobalt-based ferromagnetic layer. The manganese metal in the manganese antiferromagnetic layer is used to induce a large perpendicular magnetic anisotropy in the cobalt-based ferromagnetic layer, achieving a magnetic anisotropy of 10. 8 erg / em 3 The coercivity and perpendicular magnetic anisotropy of the ferromagnetic layer can be adjusted by changing the thickness of the manganese layer.

[0063] In step S204, a capping layer is grown on the manganese-based antiferromagnetic layer at a third preset temperature to obtain a magnetic thin film.

[0064] Through the embodiments of this disclosure, since manganese-based antiferromagnetic layers and cobalt-based ferromagnetic layers are easily oxidized in air, an Al film is grown on the manganese-based antiferromagnetic layer. The Al undergoes an oxidation reaction in air to form a dense Al2O3 film, which can protect and prevent oxidation of the multilayer magnetic film.

[0065] The following are several specific embodiments to illustrate the technical solutions of this disclosure in detail. It should be noted that the specific embodiments in the following text are for illustrative purposes only and do not limit this disclosure.

[0066] Example 1

[0067] GaAs(001) was selected as the substrate material. The semi-insulating GaAs(001) substrate was placed in a molecular beam epitaxy (MBE) preparation chamber with a vacuum level higher than 2 × 10⁻⁶. -7 Pa. After degassing and deoxidation, the substrate temperature was raised to 560℃. Then, a GaAs smoothing layer was deposited on the surface of the GaAs(001) substrate at a growth rate of 10 nm / min and a thickness of 200 nm.

[0068] Next, the temperature of the substrate was lowered to 150°C, and a cobalt-based ferromagnetic layer was grown on the surface of the smoothing layer. The cobalt-based ferromagnetic layer has a body-centered cubic structure that can match the lattice of the smoothing layer. The growth rate of the cobalt-based ferromagnetic layer was 0.2 nm / min, and the thickness of the grown layer was 1.5 nm.

[0069] Next, the temperature of the substrate was lowered to 70°C, and then a manganese-based antiferromagnetic layer was grown on the surface of the manganese-based antiferromagnetic layer with a thickness of 4 nm.

[0070] While keeping the substrate temperature at 70℃, an Al capping layer with a thickness of 3nm is grown on the manganese-based antiferromagnetic layer, thereby obtaining a magnetic thin film with a structure of GaAs / GaAs buffer / Co / Mn / Al, where GaAs buffer is a GaAs smoothing layer.

[0071] Figure 3 This is a hysteresis loop diagram of the magnetic multilayer thin film in Embodiment 1 of this disclosure.

[0072] like Figure 3 As shown, the hysteresis loop of the GaAs / GaAs buffer / Co / Mn / Al magnetic multilayer film in the out-of-plane

[001] direction is given, indicating that the cobalt-based ferromagnetic layer has good perpendicular magnetic anisotropy.

[0073] Example 2

[0074] Example 2 uses the same technical solution as Example 1, except that the cobalt (Co) film in the cobalt-based ferromagnetic layer is replaced with a cobalt-based alloy CoFe film.

[0075] Example 3

[0076] Example 3 uses the same technical solution as Example 1, except that the cobalt (Co) film in the cobalt-based ferromagnetic layer is replaced with a cobalt-based alloy Co3Mn film.

[0077] Figure 4 These are anomalous Hall curves of the magnetic films prepared using Co, CoFe, and Co3Mn films as cobalt-based ferromagnetic layers in Examples 1 to 3 of this disclosure.

[0078] like Figure 4 As shown, anomalous Hall curves are presented for magnetic multilayer films based on GaAs / GaAs buffer / Co / Mn / Al, GaAs / GaAs buffer / CoFe / Mn / Al and GaAs / GaAs buffer / Co3Mn / Mn / Al, indicating that both Co metal films and Co-based alloy films are induced to exhibit perpendicular magnetic anisotropy.

[0079] Example 4

[0080] Example 4 uses the same technical solution as Example 1, except that the thickness of the manganese-based antiferromagnetic layer is 1 nm.

[0081] Example 5

[0082] Example 5 uses the same technical solution as Example 1, the only difference being that the thickness of the manganese-based antiferromagnetic layer is 6 nm.

[0083] Example 6

[0084] Example 6 uses the same technical solution as Example 1, except that the thickness of the manganese-based antiferromagnetic layer is 8 nm.

[0085] Figure 5 Anomalous Hall curves of magnetic thin films prepared with different manganese-based antiferromagnetic layer thicknesses in Examples 1 and 4 to 6 of this disclosure.

[0086] like Figure 5 As shown, the anomalous Hall curves of GaAs / GaAs buffer / Co / Mn / Al magnetic multilayer films with different manganese-based antiferromagnetic layer thicknesses are displayed, indicating that changing the thickness of the manganese-based antiferromagnetic layer can control the vertical magnetic anisotropy and coercive field strength of the cobalt-based ferromagnetic layer.

[0087] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A magnetic thin film, comprising: substrate; A smoothing layer is disposed on the substrate; A cobalt-based ferromagnetic layer, disposed on the smoothing layer, has a body-centered cubic structure for lattice matching with the smoothing layer; A manganese-based antiferromagnetic layer is disposed on the cobalt-based ferromagnetic layer to induce the vertical magnetic anisotropy of the cobalt-based ferromagnetic layer; A capping layer, disposed on the manganese-based antiferromagnetic layer, is used to protect the magnetic thin film; The manganese-based antiferromagnetic layer is made of metallic manganese and has a thickness of 1-8 nm. The coercivity and perpendicular magnetic anisotropy of the cobalt-based ferromagnetic layer are adjusted by changing the thickness of the manganese-based antiferromagnetic layer. The thickness of the cobalt-based ferromagnetic layer is 5–200 nm.

2. The magnetic thin film according to claim 1; wherein, The material of the cobalt-based ferromagnetic layer includes any one of the following: metallic cobalt, cobalt alloy, wherein the cobalt alloy includes at least one of the following: cobalt-iron alloy, cobalt-manganese alloy.

3. The magnetic thin film according to claim 1, wherein, The material of the smoothing layer includes any one of the following: GaAs, Si, MgO, Cr, Fe, Co2MnSi, and the thickness of the smoothing layer is 5 to 200 nm.

4. The magnetic thin film according to claim 1, wherein, The substrate material includes any one of the following: GaAs, Si, MgO.

5. The magnetic thin film according to claim 1, wherein, The material of the capping layer includes any one of the following: Pt, Ta, Al, Pd, and the thickness of the capping layer is 1 to 3 nm.

6. A method for preparing a magnetic thin film according to any one of claims 1 to 5, comprising: A smooth layer is grown on the substrate at a first preset temperature; A cobalt-based ferromagnetic layer is grown on the smooth layer at a second preset temperature; At a third preset temperature, a manganese-based antiferromagnetic layer is grown on the cobalt-based ferromagnetic layer; At the third preset temperature, a capping layer is grown on the manganese-based antiferromagnetic layer to obtain a magnetic thin film.

7. The method according to claim 6, wherein, The first preset temperature is 550–570°C; The second preset temperature is: 140~160℃; The third preset temperature is 60-80℃.

8. A magnetic tunnel junction device comprising the magnetic thin film according to any one of claims 1 to 5 or the magnetic thin film prepared by the preparation method according to claim 6 or 7.

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