Method for regulating anisotropic damping in ferromagnetic / heavy metal thin film system based on stress

Abstract

The present invention discloses a method for regulating the anisotropic damping in a ferromagnetic / heavy metal thin film system based on stress. The method regulates the anisotropic magnetic damping in the ferromagnetic / heavy metal thin film system by growing the ferromagnetic / heavy metal thin film system on a flexible and bendable substrate and applying prestress during the growth process of the ferromagnetic / heavy metal thin film by utilizing the bendable characteristics of the flexible substrate. The method of the present invention has low implementation difficulty, is easy to realize the regulation of the anisotropic damping of the ferromagnetic / heavy metal thin film system, and is applicable to the field of spin-orbit-coupled electronic devices.

Description

Technical Field

[0001] The present invention belongs to the field of spintronics and relates to a method for regulating the anisotropic damping in a ferromagnetic / heavy-metal thin film system based on stress. Background Art

[0002] Spintronic devices based on magnetic thin film systems utilize the charge and spin properties of electrons for information processing, and have advantages such as high response speed, low power consumption, and non-volatility. They are key components of next-generation magnetic storage and logic devices and have become a core competitive technology in emerging electronic information. Among them, the damping coefficient of the magnetic thin film directly determines the power consumption and operating frequency of related spintronic devices. Therefore, how to regulate it has become one of the core problems and key challenges in optimizing the performance of spintronic devices currently ([1] I, Dery H. Taming spin currents[J]. Nature materials, 2011, 10(9): 647 - 648; [2] Ando K, Takahashi S, Ieda J, et al. Inverse spin-Hall effect induced by spin pumping in metallic system[J]. Journal of applied physics, 2011, 109(10): 103913.).

[0003] In recent years, it has been found that by constructing an ultra-thin ferromagnetic single-crystal thin film / semiconductor heterojunction, anisotropy of magnetic damping can be achieved in the ferromagnetic single-crystal thin film, which is expected to realize the design and fabrication of new spintronic devices such as anisotropic magnetoresistors and anisotropic magnetic sensor devices. However, the preparation process of the above ferromagnetic single-crystal thin film / semiconductor heterojunction is complex, and the requirements for the thickness and crystal structure of the thin film are extremely strict, which limits its application range in actual spintronic devices. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for regulating the anisotropic damping in a ferromagnetic / heavy-metal thin film system based on stress, and to regulate its anisotropic damping by changing the magnitude of the prestress applied by the flexible and bendable substrate during the growth process of the ferromagnetic / heavy-metal thin film system.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] Method for regulating anisotropic damping in ferromagnetic / heavy metal thin film system based on stress. According to the relationship between strain and anisotropic damping and the relationship between strain and the curvature radius of the mold, the curvature radius of the mold corresponding to the corresponding anisotropic damping is determined. Before the thin film growth, the flexible and bendable substrate is fixed on the non-magnetic metal mold with the corresponding curvature radius. After the thin film growth is completed, it is removed from the mold and naturally flattened to obtain the ferromagnetic / heavy metal thin film with the corresponding anisotropic damping.

[0007] The above method for regulating anisotropic damping in ferromagnetic / heavy metal thin film, the ferromagnetic / heavy metal thin film system is prepared by radio frequency magnetron sputtering method, and the specific steps are as follows:

[0008] (1) According to the relationship between strain and anisotropic damping and the relationship between strain and the curvature radius of the mold, the curvature radius of the mold corresponding to the corresponding anisotropic damping is determined. The mica sheet is peeled into a flexible and bendable substrate with a thickness of 10±1μm, and it is fixed on the concave or convex non-magnetic metal mold with the corresponding curvature radius;

[0009] (2) Adopt the radio frequency magnetron sputtering method, evacuate the vacuum. When the background vacuum degree of the cavity is lower than 4×10 -5 Pa, introduce argon gas, the argon gas pressure is 0.5~1Pa, radio frequency sputter the Cu target, deposit the metal buffer layer Cu on the flexible substrate in step (1), and the sputtering power is 60~80W;

[0010] (3) When the background vacuum degree of the cavity is lower than 4×10 -5 Pa, introduce argon gas, the argon gas pressure is 0.3~0.5Pa, radio frequency sputter the Fe 20 Ni 80 target, deposit the ferromagnetic metal Fe 20 Ni 80 on the buffer layer Cu, and the sputtering power is 60~80W;

[0011] (4) When the background vacuum degree of the cavity is lower than 4×10 -5 Pa, introduce argon gas, the argon gas pressure is 0.7~1Pa, radio frequency sputter the Pt target, deposit the heavy metal Pt on the Fe 20 Ni 80 , and the sputtering power is 60~80W, to obtain the ferromagnetic / heavy metal thin film with the corresponding anisotropic damping.

[0012] In step 1 of the present invention, a concave mold is used to apply tensile stress, and a convex mold is used to apply compressive stress. As the stress increases, the anisotropic damping increases.

[0013] In step 1 of the present invention, the mold curvature radius R is 20 - 30 mm, the corresponding strain ε is 1.67‰ - 2.51‰, and the strain ε is calculated by the formula ε = T / 2R, where T is the film thickness. The corresponding anisotropic damping difference is 0.35×10 -3 ~2.51×10 -3 。

[0014] Preferably, in step 3, the thickness of the buffer layer Cu is 5 nm, and the thickness of the ferromagnetic metal Fe 20 Ni 80 is 15 nm; in step 4, the thickness of the heavy metal Pt is 6 nm.

[0015] Preferably, in step 2, the argon pressure is 0.8 Pa and the sputtering power is 80 W.

[0016] Preferably, in step 3, the argon pressure is 0.3 Pa and the sputtering power is 80 W.

[0017] Preferably, in step 4, the argon pressure is 0.8 Pa and the sputtering power is 80 W.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) In the present invention, only by applying prestress during the growth of the ferromagnetic metal / heavy metal film can the anisotropic damping in the system be effectively regulated, and the controllable modulation of the anisotropic damping in the system can be achieved by changing the magnitude of the prestress; (2) The present invention does not require ferromagnetic metals or heavy metals with ultra-thin and single-crystal structures, has the characteristics of simple structure, convenient implementation, and remarkable effects, and meets the actual application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic structural diagram of the ferromagnetic / heavy metal film system in the embodiment of the present invention.

[0021] Figures 2a - 2b is a schematic diagram of applying prestress to the ferromagnetic / heavy metal film system in the embodiment of the present invention, Figure 2a is a schematic diagram of fixing the flexible substrate on the non-magnetic metal convex mold, Figure 2b is a schematic diagram of fixing the flexible substrate on the non-magnetic metal concave mold.

[0022] Figure 3 is the ferromagnetic metal damping diagram without prestress in the plane, and the anisotropic damping difference is 0.35×10 -3 。

[0023] Figures 4a - 4b is the anisotropic damping diagram of the ferromagnetic / heavy metal film system with a strain coefficient of ±1.67‰, Figure 4a is the anisotropic damping diagram under tensile strain,Figure 4b It is the damping anisotropy diagram under compressive strain.

[0024] Figures 5a - 5b It is the anisotropic damping diagram of the ferromagnetic / heavy metal thin film system with a strain coefficient of ±2.56‰. Figure 5a It is the damping anisotropy diagram under tensile strain. Figure 5b It is the damping anisotropy diagram under compressive strain.

[0025] Figure 6 It is the relationship diagram between the anisotropic damping difference and the strain magnitude. Specific implementation mode

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] In the following embodiments, the magnetron sputtering instrument used is purchased from Shenyang Scientific Instrument Co., Ltd., and the model is JPG450 single-chamber magnetron sputtering.

[0028] As Figure 1 shown, the method for regulating the anisotropic damping in the ferromagnetic / heavy metal thin film system based on stress of the present invention, the ferromagnetic / heavy metal thin film system includes a mica substrate, a metal buffer layer Cu, a ferromagnetic metal Fe 20 Ni 80 and a heavy metal layer Pt.

[0029] The present invention regulates the anisotropic damping of the system by applying prestress through a flexible and bendable substrate during the growth process of the ferromagnetic / heavy metal thin film system. The specific process of applying prestress is as Figures 2a - 2b shown. Before film deposition, the flexible and bendable substrate is fixed on a non-magnetic metal concave (convex) mold, and then the ferromagnetic / heavy metal thin film system is deposited on the above substrate to apply prestress, and the stress magnitude is realized by changing the curvature radius of the mold.

[0030] Example 1

[0031] The method for regulating the anisotropic damping in the ferromagnetic / heavy metal thin film based on stress is specifically as follows:

[0032] Step 1, the flexible and bendable substrate used is a mica sheet, which is fixed on a concave mold with a curvature radius of 30 mm before film growth, and the thickness of the mica sheet is 10 μm.

[0033] Step 2, when the background vacuum degree in the cavity is lower than 4×10 -5 Pa, argon is introduced, the argon pressure is 0.8 Pa, and the Cu target is sputtered by radio frequency to deposit a metal buffer layer Cu with a thickness of 5 nm on the above flexible substrate, and the sputtering power is 80 W.

[0034] Step 3, when the background vacuum degree in the cavity is lower than 4×10-5 When the pressure is 0.3 Pa, argon gas is introduced, and the argon gas pressure is 0.3 Pa. Fe is sputtered by radio frequency. 20 Ni 80 target, and ferromagnetic metal Fe with a thickness of 15 nm is deposited on the above flexible substrate. 20 Ni 80 , and the sputtering power is 80 W.

[0035] Step 4, when the background vacuum degree of the cavity is lower than 4×10 -5 Pa, argon gas is introduced, the argon gas pressure is 0.8 Pa, and a Pt target is sputtered by radio frequency. Heavy metal Pt with a thickness of 6 nm is deposited on the above flexible substrate, and the sputtering power is 80 W.

[0036] Example 2

[0037] This example is basically the same as Example 1, and the only difference is that a convex mold is used and the radius of curvature of the convex mold is 30 mm.

[0038] Example 3

[0039] This example is basically the same as Example 1, and the only difference is that the radius of curvature of the concave mold is 20 mm.

[0040] Example 4

[0041] This example is basically the same as Example 1, and the only difference is that a convex mold is used and the radius of curvature of the convex mold is 20 mm.

[0042] Comparative Example 1

[0043] This comparative example is basically the same as Example 1, and the only difference is that a convex mold is used and the radius of curvature of the convex mold is 10 mm. When the radius of curvature of the convex mold is 10 mm, the prepared sample has a large thickness non-uniformity, which has a great influence on the performance.

[0044] Comparative Example 2

[0045] This comparative example is basically the same as Example 1, and the only difference is that the radius of curvature of the concave mold is 20 mm. When the radius of curvature of the concave mold is 10 mm, the prepared sample also has a large thickness non-uniformity, which has a great influence on the performance.

[0046] The ferromagnetic resonance tests are carried out on thin film samples with different prestresses. Figure 3 It is the ferromagnetic metal damping diagram without prestress in the plane, and the anisotropic damping difference is 0.35×10 -3 . Figures 4a - 4b It is the anisotropic damping diagram of the ferromagnetic / heavy metal thin film system with a strain coefficient of ±1.67‰. Figure 4a It is the damping change diagram of the sample prepared in Example 1. Under tensile strain, the damping anisotropy changes from 0.35×10-3 Increased to 1.56×10 -3 , Figure 4b is the damping change diagram of the sample prepared in Example 2. The damping anisotropy under compressive strain increases from 0.35×10 -3 to 0.62×10 -3 . Figures 5a - 5b is the anisotropic damping diagram of the ferromagnetic / heavy metal thin film system with a strain coefficient of ±2.56‰. Figure 5a is the damping change diagram of the sample prepared in Example 3. The damping anisotropy under tensile strain increases from 0.35×10-3 to 2.51×10 -3 , Figure 5b is the damping change diagram of the sample prepared in Example 4. The damping anisotropy under compressive strain increases from 0.35×10 -3 to 2.28×10 -3 . Figure 6 is the relationship diagram between the anisotropic damping difference and the strain magnitude.

Claims

1. A method for regulating the anisotropic damping in a ferromagnetic / heavy metal thin film system based on stress, characterized in that, According to the relationship between strain and anisotropic damping and the relationship between strain and the curvature radius of the mold, determine the curvature radius of the mold corresponding to the corresponding anisotropic damping. Before film growth, fix the flexible and bendable substrate on the non-magnetic metal mold with the corresponding curvature radius. After film growth is completed, remove it from the mold and let it flatten naturally to obtain a ferromagnetic / heavy metal film with the corresponding anisotropic damping.

2. The method according to claim 1, wherein The specific steps are as follows: (1) According to the relationship between strain and anisotropic damping and the relationship between strain and the curvature radius of the mold, determine the curvature radius of the mold corresponding to the corresponding anisotropic damping. Peel the mica sheet into a flexible and bendable substrate with a thickness of 10 ± 1 μm, and fix it on the concave or convex non-magnetic metal mold with the corresponding curvature radius; (2) Adopt the radio frequency magnetron sputtering method, evacuate the vacuum, and when the background vacuum degree of the cavity is lower than 4×10 -5 Pa, introduce argon gas, the argon gas pressure is 0.5 - 1 Pa, sputter the Cu target by radio frequency, deposit the metal buffer layer Cu on the flexible substrate in step (1), and the sputtering power is 60 - 80 W; (3) When the background vacuum degree of the cavity is lower than 4×10 -5 Pa, argon gas is introduced, and the argon gas pressure is 0.3 - 0.5 Pa. Radio frequency sputtering of the Fe 20 Ni 80 target is carried out to deposit ferromagnetic metal Fe 20 Ni 80 on the buffer layer Cu, and the sputtering power is 60 - 80 W; (4) When the base vacuum degree of the cavity is lower than 4×10 -5 Pa, argon gas is introduced, the argon gas pressure is 0.7 - 1 Pa, and the Pt target is sputtered by radio frequency. On Fe 20 Ni 80 Heavy metal Pt is deposited, the sputtering power is 60 - 80 W, and a ferromagnetic / heavy metal film with corresponding anisotropic damping is prepared.

3. The method according to claim 2, wherein In step 1, a tensile stress is applied using a concave mold, and a compressive stress is applied using a convex mold.

4. The method according to claim 2, wherein In Step 1, the mold curvature radius R is 20 - 30 mm, the corresponding strain ε is 1.67‰ - 2.51‰, and the strain ε is calculated by the formula ε = T / 2R, where T is the film thickness; the corresponding anisotropic damping difference is 0.35×10 -3 ~2.51×10 -3 .

5. The method according to claim 2, characterized in that In Step 3, the thickness of the buffer layer Cu is 5 nm, and the thickness of the ferromagnetic metal Fe 20 Ni 80 is 15 nm; in Step 4, the thickness of the heavy metal Pt is 6 nm.

6. The method according to claim 2, wherein In step 2, the argon pressure is 0.8 Pa and the sputtering power is 80 W.

7. The method according to claim 2, wherein In step 3, the argon pressure is 0.3 Pa and the sputtering power is 80 W.

8. The method according to claim 2, wherein In step 4, the argon pressure is 0.8 Pa and the sputtering power is 80 W.

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