A method for obtaining chiral coupling in ferrimagnetic alloys

Abstract

A method for obtaining chiral coupling in ferrimagnetic alloy belongs to the technical field of new materials, and comprises the following steps: 1) a step of depositing tantalum Ta as a seed layer on a Si / SiO2 substrate by using a direct current magnetron sputtering technology; 2) on the basis of the step 1), a step of depositing platinum Pt as a heavy metal layer on the Ta by using the direct current magnetron sputtering technology; 3) on the basis of the step 2), a step of preparing a TM-RE ferrimagnetic alloy on a multilayer film by using a method of direct current co-sputtering of a magnetic transition metal or alloy TM and a rare earth metal RE; 4) on the basis of the step 3), a step of depositing Ta as a cover layer on the multilayer film by using the direct current magnetron sputtering technology, so as to finally obtain a ferrimagnetic multilayer film; and 5) chiral coupling magnetic structure is constructed by using gallium ion irradiation to change magnetic anisotropy of the ferrimagnetic multilayer film. The chiral coupling can be used to construct a race track memory based on the ferrimagnetic, and the race track memory is expected to show a lower power consumption application potential than a traditional ferromagnetic system in a new type of calculation.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically a method for enabling chiral coupling in ferrimagnetic alloys. Background Technology

[0002] For decades, semiconductor information technology has been developing rapidly in accordance with the predictions of Moore's Law. However, as the size of complementary metal-oxide-semiconductor (CMOS) devices gradually approaches their physical limits, miniaturization has become extremely difficult, forcing people to seek and develop computing devices based on new principles. On the other hand, the existing von Neumann computer architecture consists of separate data processing units and data storage units. If the speed of data storage and transmission does not keep up with the operating speed of the data processing units, the speed gap between data storage and processing units will widen, resulting in the memory wall problem, which is considered one of the main bottlenecks limiting the further development of the overall performance of the computer. Therefore, the development of new in-memory computing devices based on new principles is of great significance for the next generation of high-performance computers. Utilizing the spin properties of electrons to carry information and perform data processing functions is expected to realize low-power, high-speed, and non-volatile spintronic chips, thereby building a new generation of high-performance computers. In particular, the discovery of chiral magnetic structures in nanomagnetic systems in recent years [1,2] has brought new opportunities for the development of next-generation spintronic devices. These chiral magnetic structures have nanoscale dimensions and can be electrically manipulated with low power consumption, making them very suitable for the computational needs of big data processing and storage in the digital age. Recent experimental and theoretical studies have shown that high-speed directional movement of domain walls can be driven by applying current to a magnetic system [3,4], and various computational operations can be achieved by designing device geometry and magnetic control [5]. However, most current research focuses on ferromagnetic materials. Ferromagnetic materials have large stray fields and are sensitive to external magnetic fields, which leads to a decrease in the integration and reliability of spintronic devices based on ferromagnetic materials. At the same time, the spin dynamics process of ferromagnetic materials is generally on the nanosecond scale, which limits the further improvement of the device response speed. In contrast, subferromagnetic materials greatly reduce stray fields at their magnetization compensation point, which can improve the integration and stability of spintronic devices [6]. Meanwhile, studies have shown that near the compensation point, there is a higher spin-orbit torque efficiency and a longer spin coherence length, exhibiting ultrafast magnetodynamic behavior, which can reduce the response speed of spintronic devices to picoseconds, which can reduce the energy consumption of spintronic devices [7]. It should be noted that although fully compensated antiferromagnets also possess characteristics such as a net magnetic moment close to zero and ultrafast magnetodynamic velocities, subferromagnetic materials are easier to detect, and their magnetic moments can be manipulated using spin torque control methods similar to those used for ferromagnets. This means that subferromagnets have a greater advantage over antiferromagnetic materials in terms of reading, writing, and manipulating magnetization information.

[0003] Therefore, manipulating the ferrimagnetic magnetic structure is crucial for realizing in-memory computing devices. This invention mainly utilizes ion irradiation technology compatible with CMOS processes to construct a ferrimagnetic chiral coupled magnetic structure, providing theoretical and technical guidance for the development of high-performance spintronic in-memory computing devices based on the principle of ferrimagnetic chiral magnetic structure.

[0004] [1]Luo Z, Dao TP, Hrabec A, et al. Chirally coupled nanomagnets[J]. Science, 2019, 363(6434): 1435-1439.

[0005] [2]Luo Z,Hrabec A,Dao TP,et al.Current-driven magnetic domain-walllogic[J].Nature,2020,579,214-218.

[0006] [3]Cai K, Zhu Z, Lee JM, et al. Ultrafast and energy-efficient spin-orbit torque switching in compensated ferrimagnets[J]. Nature Electronics, 2020, 3(1):37-42.

[0007] [4]Caretta L,Mann M,Büttner F.et al.Fast current-driven domain walls and small skyrmions in a compensated ferrimagnet[J].Nature Nanotech,2018,13:1154-1160.

[0008] [5]Kumar D, Jin T, Sbiaa R, et al. Domain wall memory: Physics, materials, and devices [J]. Physics Reports, 2022,958:1-35.

[0009] [6]Je SG, Rojas-Sánchez JC, Pham TH, et al.Spin-orbit torque-inducedswitching in ferrimagnetic alloys:Experiments and modeling[J].Applied PhysicsLetters,2018,112(6):062401.

[0010] [7]Kim KJ,Kim SK,HirataY,et al.Fast domain wall motion in thevicinity of the angular momentum compensation temperature of ferrimagnets[J].Nature materials,2017,16(12):1187-1192. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention aims to solve the technical problem of providing a spin-based logic architecture that offers non-volatile data retention, low power consumption, and cascadability, thus expanding the technology roadmap for complementary metal-oxide-semiconductor (CMOS) logic. Domain wall structures offer advantages in information processing and storage, including high speed, high density, low volatility, and flexible design. However, this approach relies on domain wall manipulation using an external magnetic field, which limits their implementation in dense, large-scale chips. This invention, for the first time, utilizes gallium ion irradiation to achieve chiral coupling in a ferrimagnetic alloy, leveraging the Dzyaloshinskii-Moriya interface to achieve chiral coupling between out-of-plane and in-plane magnetic regions of laterally adjacent domains. This concept combines the ultrafast magnetodynamic behavior of ferrimagnets (such as ultrafast magnetization reversal manipulated by spin-orbit torque) and low stray field characteristics to construct all-electrically manipulated logic devices for ferrimagnetic domains, potentially demonstrating faster, denser, and more stable applications than traditional ferromagnetic systems in novel computing applications.

[0012] The technical solution of the present invention to solve the aforementioned technical problem is to provide a method for obtaining chiral coupling in a ferrimagnetic alloy, comprising the following steps:

[0013] 1) The step of depositing tantalum (Ta) as a seed layer on a Si / SiO2 substrate using DC magnetron sputtering technology;

[0014] 2) Based on step 1), the step of depositing platinum (Pt) as a heavy metal layer on the seed layer Ta using DC magnetron sputtering technology;

[0015] 3) Based on step 2), the step of preparing TM-RE ferrimagnetic alloy on Ta / Pt multilayer film by DC co-sputtering of magnetic transition metal or alloy (TM) and rare earth metal (RE) targets;

[0016] 4) Based on step 3), a step of re-depositing Ta as a capping layer on the multilayer film using DC magnetron sputtering technology is adopted, and finally a Ta / Pt / TM-RE ferrimagnetic layer / Ta multilayer film structure is obtained on the Si / SiO2 substrate.

[0017] 5) By using gallium ion irradiation to change the vertical magnetic anisotropy of the ferrimagnetic thin film from out-of-plane to in-plane, a ferrimagnetic chiral coupling structure is constructed.

[0018] Further, in step 1), a 1-2 nm Ta layer is deposited on the Si / SiO2 substrate as a seed layer, with sputtering power, background, and working pressure of 20-75 W, 1-5 × 10⁻⁶ W, and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr.

[0019] Furthermore, in step 2), a 5-7 nm Pt layer is deposited on the seed layer Ta as a heavy metal layer, with sputtering power, background, and working pressure of 20-75 W, 1-5 × 10⁻⁶ W, and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr.

[0020] Further, in step 3), a 6-8 nm TM-RE ferrimagnetic alloy is prepared on a Ta / Pt multilayer film. The sputtering power of the TM target is fixed, and the sputtering power of the RE target is changed to alter the sputtering rate of RE in the TM-RE layer, thereby changing the atomic ratio of TM and RE. The background and working gas pressures are 1-5 × 10⁻⁶. -8 Torr and 3-10mTorr.

[0021] Furthermore, in step 4), a 1-2 nm Ta layer is deposited on the multilayer film as a capping layer to prevent oxidation of the TM-RE layer. The sputtering power, background, and working pressure are 20-75 W, 1-5 × 10⁻⁶ W, and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr.

[0022] Furthermore, the transition metal and rare earth metal of the TM-RE ferrimagnetic layer are Co and Gd, respectively, or one of the magnetic transition metal-rare earth systems of CoTb, GdFeCo, FeGd, and FeTb.

[0023] Furthermore, the process includes the following steps: placing Ta, Pt, Co, and Gd targets with a purity of 99.99% into the magnetron sputtering target positions, where the background vacuum of the sputtering chamber is better than 5 × 10⁻⁶. -8During the Torr process, 99.99% pure argon gas is introduced into the sputtering chamber, and the argon gas flow rate is adjusted to make the argon gas pressure 10mTorr. Ta, Pt, Co, and Gd targets are pre-sputtered respectively, with a power of 30W for each.

[0024] This invention also provides a chiral coupled multilayer film structure, prepared by the methods described above. Furthermore, it provides a chiral coupling method for constructing this multilayer film magnetic structure using gallium ion beam irradiation technology.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention is the first to utilize gallium ion irradiation to change the vertical magnetic anisotropy of a ferrimagnetic thin film from out-of-plane to in-plane. Based on this method, a ferrimagnetic chiral coupling structure is constructed, and chiral coupling of the magnetic structure is successfully realized in a ferrimagnetic multilayer film. This coupling is still maintained at the micrometer scale.

[0027] (1) Gallium ion beam irradiation in this invention provides a convenient and controllable technical method for the anisotropy modulation of ferrimagnetic materials.

[0028] (2) This invention utilizes gallium ion beams to control the anisotropy of ferrimagnetism, thereby constructing ferrimagnetic chiral coupling. The realization of this technology will combine the ultrafast magnetodynamic behavior and low stray field characteristics of ferrimagnetism with all-electric synchronous switches, opening up a new path for realizing ultra-high speed, low energy consumption nanomagnetic logic gates and memory devices.

[0029] (3) In addition to the CoGd system described in the embodiments, the subferromagnetic material in this invention can also be identified as a magnetic transition metal-rare earth, such as CoTb, GdFeCo, FeGd, FeTb, etc. The regulation effect is similar to that in the embodiments of this invention. The scope of this invention is equivalently limited to similar subferromagnetic alloys. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the multilayer membrane structure of the present invention;

[0031] Figure 2 This is a schematic diagram of the gallium ion irradiation region and Hall bar test of the present invention;

[0032] Figure 3 The initial state R of the multilayer film of this invention xy -B z curve;

[0033] Figure 4 To illustrate the different accelerating voltages and the same gallium ion irradiation doses of the multilayer films at room temperature R in this invention, xy -B z Curves, with the inset showing a scanning electron microscope image after irradiation;

[0034] Figure 5 This is a schematic diagram of the present invention, which uses gallium ion irradiation to change magnetic anisotropy and thus achieve chiral coupling. The black area in the diagram is a ferrimagnetic multilayer film, and the white area is the gallium ion irradiation area.

[0035] Figure 6 The surface morphology of this sample after gallium ion irradiation is shown in Figure W. OOP and W IP These represent the machining width with in-plane magnetic anisotropy at the machining area and the machining width with out-of-plane magnetic anisotropy within the machining area, respectively.

[0036] Figure 7 This is a chiral coupled magneto-optical Kerr micrograph of the subferromagnetic multilayer film structure of this invention. The dashed line represents W. IP The area inside the dashed line is W. OOP The area outside the dashed line represents the base. These represent the upward and downward directions of the out-of-plane magnetic field, respectively. Detailed Implementation

[0037] Specific embodiments of the present invention are given below. These specific embodiments are only used to further illustrate the present invention in detail and do not limit the scope of protection of the claims of the present invention.

[0038] This invention provides a method for obtaining chiral coupling in a ferrimagnetic alloy (hereinafter referred to as the method), characterized by comprising the following steps:

[0039] Step 1: Deposit a 1-2 nm tantalum (Ta) layer as a seed layer on a Si / SiO2 substrate using DC magnetron sputtering technology. The sputtering power, background, and working pressure are 20-75 W, 1-5 × 10⁻⁶ W, and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr;

[0040] Step 2: Based on Step 1, a 5-7 nm platinum (Pt) layer is deposited on the seed layer Ta using DC magnetron sputtering technology. The sputtering power, background, and working pressure are 20-75 W and 1-5 × 10⁻⁶, respectively. -8 Torr and 3-10mTorr;

[0041] Step 3: Based on Step 2, a 6-8 nm TM-RE ferrimagnetic alloy is prepared on a Ta / Pt multilayer film using DC co-sputtering with magnetic transition metal or alloy (TM) and rare earth metal (RE) targets. The sputtering power of the TM target is fixed, while the sputtering power of the RE target is changed to alter the sputtering rate of RE in the TM-RE layer, thereby changing the atomic ratio of TM and RE. The background and working gas pressures are 1-5 × 10⁻⁶. -8 Torr and 3-10mTorr.

[0042] Step 4: Based on Step 3, a 1-2 nm Ta layer is deposited on the multilayer film using DC magnetron sputtering to prevent oxidation of the TM-RE layer. The sputtering power, background, and working pressure are 20-75 W and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr were used to finally obtain a Ta / Pt / TM-RE ferrimagnetic layer / Ta multilayer film structure on a Si / SiO2 substrate.

[0043] Step 5: The multilayer film structure prepared in steps 1-4 is fabricated into a Hall rod device for testing using ultraviolet exposure, argon ion etching, and lift-off techniques.

[0044] Step 6: Using a focused ion beam scanning electron microscope (FEI Helios 5CX), irradiate selected areas of the Hall rod device prepared in Step 5 with gallium ions at an accelerating voltage and current of 16-30 kV and 7.7-40 pA, with an irradiation dose of 10-300 μC / cm². 2 .

[0045] Step 7: Measure the anomalous Hall resistance of the Hall rod device in Step 6 before and after gallium ion irradiation using a physical property measurement system (PPMS-s9t, Quantum Design) to characterize its magnetoelectric transport properties and observe the changes in magnetic anisotropy.

[0046] Step 8: Use a magneto-optical Kerr microscope to measure the change of magnetic domains in a selected area of ​​the Hall bar device in Step 6 with the external magnetic field, observe and record the chiral coupling micrograph of the magnetic structure.

[0047] Example 1

[0048] (1) The diameter Ta, Pt, Co, and Gd targets with a thickness of 3 mm and a purity of 99.99% are placed in the magnetron sputtering target position, which is tilted.

[0049] (2) Clean 1×1cm with acetone and alcohol. 2 For Si / SiO2 substrates, place the cleaned substrates into the sample tray, and then place the tray into the sample transfer chamber.

[0050] (3) Turn on the mechanical pump and molecular pump in the sample transfer chamber to evacuate the sample transfer chamber to a vacuum level of 5 × 10⁻⁶. -6 Below Torr;

[0051] (4) Open the sample transfer chamber and the main chamber gate valve to transfer the sample tray into the main chamber;

[0052] (5) When the background vacuum of the sputtering chamber is better than 5×10 -8During the Torr process, 99.99% pure argon gas is introduced into the sputtering chamber, and the argon gas flow rate is adjusted to make the argon gas pressure 10mTorr. Ta, Pt, Co, and Gd targets are pre-sputtered respectively, with a power of 30W for each.

[0053] (6) Using a program control method, the argon flow rate is automatically adjusted, the ignition pressure is 10 mTorr, the sputtering pressure is 3 mTorr, and the tray rotates at a constant speed to make the film evenly distributed on the substrate. 1 nm Ta is sputtered sequentially with a power of 75 W for 20 s; 5 nm Pt with a power of 75 W for 50 s; Co and Gd are co-sputtered with a CoGd thickness of 7 nm, with powers of 75 W and 15 W respectively for 90 s; and 1 nm Ta with a power of 75 W for 20 s.

[0054] (7) After sputtering is completed, the program will automatically shut down and restore the vacuum state of the main chamber. Then, the sampling operation will be carried out. Open the gate valves of the main chamber and the sample transfer chamber, pull the sample tray back to the sample chamber with the sample transfer rod, close the gate valves of the main chamber and the sample transfer chamber, inject N2 into the sample chamber, and wait for the air pressure to reach atmospheric pressure before taking out the tray and removing the sample.

[0055] (8) Multilayer membrane structure as shown in the attached figure Figure 1 As shown.

[0056] Example 2

[0057] (1) Hall rod devices with dimensions of 10μm×5μm were fabricated using ultraviolet exposure, argon ion etching and lift-off technology;

[0058] (2) The anomalous Hall resistance of the Hall rod device after irradiation was measured using a physical property measurement system (PPMS-s9t, Quantum Design) to characterize its magnetoelectric transport properties. The magnetic field sweep range was -300mT to 300mT. Figure 3 The anomalous Hall terminal resistance R to be measured xy R varies with the applied magnetic field in the z-direction xy -B z The results show that the thin film has good perpendicular magnetic anisotropy. Furthermore, after temperature-dependent anomalous Hall terminal resistance R... xy Measurements confirmed that the multilayer film possesses ferrimagnetic properties. Specifically, at a temperature of approximately 260 K, there is almost no anomalous Hall resistance, indicating that the magnetic moments of Co and Gd compensate for each other at this temperature. As the temperature rises past the compensation point, the magnetism of the CoGd layer changes from Co-dominant to Gd-dominant, causing the magnetic moments of the Co sublattice to reverse, resulting in a reversal of the polarity of the anomalous Hall resistance.

[0059] Example 3

[0060] (1) Hall rod devices with dimensions of 35μm×10μm were fabricated using ultraviolet exposure, argon ion etching and lift-off technology;

[0061] (2) Gallium ion irradiation was performed on a selected region (10 μm × 10 μm) using a focused ion beam scanning electron microscope (FEI Helios 5CX) at accelerating voltages of 5, 8, 16, and 30 kV and accelerating currents of 23 pA, with an irradiation dose of 57 μC / cm. 2 .

[0062] (3) The anomalous Hall resistance of the Hall rod device after irradiation was measured using a physical property measurement system (PPMS-s9t, Quantum Design) to characterize its magnetoelectric transport properties (see attached). Figure 2 As shown), the magnetic field sweep range is -600mT to 600mT, from the attached... Figure 4 As can be seen from the data, under the same irradiation dose, as the gallium ion irradiation energy is continuously increased, the thin film tends to gradually change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. Specifically, this is manifested in the gradual increase of the magnetization saturation field, indicating that gallium ion irradiation successfully modulates the easy magnetization direction of CoGd, i.e., magnetic anisotropy.

[0063] Example 4

[0064] (1) Using a focused ion beam scanning electron microscope (FEI Helios 5CX), the attached particles were observed at an accelerating voltage of 30 kV and an accelerating current of 23 pA. Figure 5 Gallium ion irradiation was performed on a selected area at a dose of 57 μC / cm². 2 .

[0065] (2) The surface morphology of the irradiated film was characterized using atomic force microscopy, as shown in the attached figure. Figure 6 As shown, where W IP W represents the width of the region where magnetic anisotropy changes after gallium ion irradiation; OOP This represents the width of the region that maintains perpendicular magnetic anisotropy after being modified by gallium ion irradiation.

[0066] (3) The above structure was characterized in detail using a magneto-optical Kerr microscope. The specific operation was as follows (see appendix). Figure 7 ae): (1) positive saturation magnetization; (2) reverse increase of magnetic field until the matrix magnetization reverses, at which time due to the existence of chiral coupling W OOP The Co magnetic moment in the region remains upward; (3) Continue to increase the magnetic field in the opposite direction. When the Zeeman of the reverse magnetic field can overcome the effective field of chiral coupling, W OOP (4) Increase the magnetic field in the positive direction until the Co magnetic moment of the matrix reverses, and similarly, W OOPThe magnetic moment of Co in the region remains magnetized downwards; (5) the magnetic field continues to increase in the positive direction, W OOP The Co magnetic moment flips within the region.

[0067] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A method for obtaining chiral coupling in a ferrimagnetic alloy, characterized in that, The method includes the following steps: 1) The step of depositing tantalum Ta as a seed layer on a Si / SiO2 substrate using DC magnetron sputtering technology; 2) Based on step 1), the step of depositing platinum Pt as a heavy metal layer on the seed layer Ta using DC magnetron sputtering technology; 3) Based on step 2), the step of preparing TM-RE ferrimagnetic alloy on Ta / Pt multilayer film by DC co-sputtering of magnetic transition metal or alloy TM and rare earth metal RE target; 4) Based on step 3), a step of re-depositing Ta as a capping layer on the multilayer film using DC magnetron sputtering technology is adopted, and finally a Ta / Pt / TM-RE ferrimagnetic layer / Ta multilayer film structure is obtained on the Si / SiO2 substrate. 5) By using gallium ion irradiation to change the perpendicular magnetic anisotropy of the ferrimagnetic thin film from out-of-plane to in-plane, a ferrimagnetic chiral coupling structure was constructed, and chiral coupling of the magnetic structure was realized in the ferrimagnetic multilayer film. In step 1), a 1-2 nm Ta layer is deposited on a Si / SiO2 substrate as a seed layer, with sputtering power, background, and working pressure of 20-75 W, 1-5 × 10⁻⁶ W, and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr; In step 2), a 5-7 nm Pt layer is deposited on the seed layer Ta as a heavy metal layer, with sputtering power, background, and working pressure of 20-75 W and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr; In step 3), a 6-8 nm TM-RE ferrimagnetic alloy is prepared on a Ta / Pt multilayer film. The sputtering power of the TM target is fixed, and the sputtering power of the RE target is changed to alter the sputtering rate of RE in the TM-RE layer, thereby changing the atomic ratio of TM and RE. The background and working gas pressures are 1-5 × 10⁻⁶. -8 Torr and 3-10mTorr; In step 4), a 1-2 nm Ta layer is deposited on the multilayer film as a capping layer to prevent oxidation of the TM-RE layer. The sputtering power, background, and working pressure are 20-75 W, 1-5 × 10⁻⁶ W, and 1-5 × 10⁻⁶ W, respectively. -8 Torr and 3-10mTorr.

2. The method for obtaining chiral coupling in a hypoferromagnetic alloy according to claim 1, characterized in that: The transition metal and rare earth metal of the TM-RE ferrimagnetic layer are Co and Gd, respectively, or one of the magnetic transition metal-rare earth systems of CoTb, GdFeCo, FeGd, and FeTb.

3. The method for obtaining chiral coupling in a hypoferromagnetic alloy according to claim 1 or 2, characterized in that: Includes the following steps: Ta, Pt, Co, and Gd targets with a purity of 99.99% were placed in the magnetron sputtering target positions, and the background vacuum of the sputtering chamber was better than 5 × 10⁻⁶. -8 During the Torr process, 99.99% pure argon gas is introduced into the sputtering chamber, and the argon gas flow rate is adjusted to make the argon gas pressure 10 mTorr. Ta, Pt, Co, and Gd targets are pre-sputtered respectively, with a power of 30W for each.

4. A subferromagnetic chiral coupled multilayer film structure, characterized in that: Prepared by the method described in any one of claims 1-3.

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