United States

Cr1/3NbS2, the first known magnetic soliton system, has abundant magnetic phases like chiral helimagnetic order (HM), chiral conical phase, chiral soliton lattice (CSL), tilted chiral soliton lattice and forced ferromagnetic (FM) due to the competition between Dzyaloshinskii–Moriya exchange, Heisenberg interaction, magnetocrystalline anisotropy and Zeeman energy (1, 2). These rich magnetic textures display attractive properties, such as magnetocaloric effect (3), topological Hall effect and planar Hall effect (4), etc. Especially, magnetic soliton, a real-space topological magnetic structure like skyrmion, owns topological protection properties and quasi-particle nature which makes Cr1/3NbS2 a promising platform for the spintronic devices (5, 6).
Recently, we have studied the transition of various magnetic structures by magnetoresistance (MR) (7), a.c. magnetic susceptibility (7), and Lorentz transmission electron microscopy (L-TEM). As shown in Fig. 1(a), when a magnetic field was applied along the c-axis (H ‖ c - axis) at low temperatures, we found signatures of weak antilocalization which may originate from the strong spin–orbit coupling of Cr1/3NbS2. When the magnetic field was applied along the ab-plane (H ‖ ab - plane), the transition from HM to CSL and FM can be detected by a.c. magnetic susceptibility (Fig. 1(b)). To better understand CSL, we adopted L-TEM measurement. As shown in Fig. 1(c) and (d), a helical period longer than theoretical calculations (~48 nm) and showing opposite chirality due to grain boundary modulation were observed in some regions on the sample. The reason for the difference in period can be the uneven content of Cr intercalation. This may provide an effective way to regulate the helical period, thus facilitating its practical application.&lt;br&gt;

**References:** &lt;br&gt;
(1) T. Miyadai, K. Kikuchi, H. Kondo, et al., J. Phys. Soc. Jpn. 52 (4), 1394-1401 (1983).&lt;br&gt;
(2) Y. Togawa, T. Koyama, K. Takayanagi, et al., Phys. Rev. Lett. 108 (10), 107202 (2012).&lt;br&gt;
(3) N. J. Ghimire, M. A. McGuire, D. S. Parker, et al., Phys. Rev. B 87 (10), 104403 (2013).&lt;br&gt;
(4) D. A. Mayoh, J. Bouaziz, A. E. Hall, et al., Phys. Rev. Research 4 (1), 013134 (2022).&lt;br&gt;
(5) Y. Togawa, T. Koyama, Y. Nishimori, et al., Phys. Rev. B 92 (22), 220412 (2015).&lt;br&gt;
(6) L. Wang, N. Chepiga, D. K. Ki, et al., Phys. Rev. Lett. 118 (25), 257203 (2017).&lt;br&gt;
(7) X. Li, Z. Li, H. Li, et al., Appl. Phys. Lett. 120 (11), 112408 (2022).&lt;br&gt;

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MMM 2022

Angular dependent magnetoresistance and magnetic soliton lattice in Cr1/3NbS2

Cr1/3NbS2, the first known magnetic soliton system, has abundant magnetic phases like chiral helimagnetic order (HM), chiral conical phase, chiral soliton lattice (CSL), tilted chiral soliton lattice and forced ferromagnetic (FM) due to the competition between Dzyaloshinskii–Moriya exchange, Heisenberg interaction, magnetocrystalline anisotropy and Zeeman energy (1, 2). These rich magnetic textures display attractive properties, such as magnetocaloric effect (3), topological Hall effect and planar Hall effect (4), etc. Especially, magnetic soliton, a real-space topological magnetic structure like skyrmion, owns topological protection properties and quasi-particle nature which makes Cr1/3NbS2 a promising platform for the spintronic devices (5, 6).
Recently, we have studied the transition of various magnetic structures by magnetoresistance (MR) (7), a.c. magnetic susceptibility (7), and Lorentz transmission electron microscopy (L-TEM). As shown in Fig. 1(a), when a magnetic field was applied along the c-axis (H ‖ c - axis) at low temperatures, we found signatures of weak antilocalization which may originate from the strong spin–orbit coupling of Cr1/3NbS2. When the magnetic field was applied along the ab-plane (H ‖ ab - plane), the transition from HM to CSL and FM can be detected by a.c. magnetic susceptibility (Fig. 1(b)). To better understand CSL, we adopted L-TEM measurement. As shown in Fig. 1(c) and (d), a helical period longer than theoretical calculations (~48 nm) and showing opposite chirality due to grain boundary modulation were observed in some regions on the sample. The reason for the difference in period can be the uneven content of Cr intercalation. This may provide an effective way to regulate the helical period, thus facilitating its practical application. 

**References:** 
(1) T. Miyadai, K. Kikuchi, H. Kondo, et al., J. Phys. Soc. Jpn. 52 (4), 1394-1401 (1983). 
(2) Y. Togawa, T. Koyama, K. Takayanagi, et al., Phys. Rev. Lett. 108 (10), 107202 (2012). 
(3) N. J. Ghimire, M. A. McGuire, D. S. Parker, et al., Phys. Rev. B 87 (10), 104403 (2013). 
(4) D. A. Mayoh, J. Bouaziz, A. E. Hall, et al., Phys. Rev. Research 4 (1), 013134 (2022). 
(5) Y. Togawa, T. Koyama, Y. Nishimori, et al., Phys. Rev. B 92 (22), 220412 (2015). 
(6) L. Wang, N. Chepiga, D. K. Ki, et al., Phys. Rev. Lett. 118 (25), 257203 (2017). 
(7) X. Li, Z. Li, H. Li, et al., Appl. Phys. Lett. 120 (11), 112408 (2022). 

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technical paper

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

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MMM 2022 is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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Half-metallic Heusler alloys are of high interest to the material research community due to their potential application in spintronic devices. We have synthesized one such compound, CoFeVGe, using arc melting and high-vacuum annealing at 600oC for 48 hours. The room temperature x-ray diffraction of the sample exhibits a cubic crystal structure without secondary phases. The sample shows a single magnetic transition at its Curie temperature of 249 K, Fig. 1(a). The high field (3T) magnetization measured at 100 K is 41 emu/g. We also observed that the Curie temperature of the sample can be increased to near room temperature with slightly changing the elemental composition. The sample with composition Co1.25Fe0.75VGe remains cubic in crystal structure, and it exhibits a Curie temperature of 294 K and saturation magnetization at 100 K of 36 emu/g. Our first principle calculations of CoFeVGe and Co1.25Fe0.75VGe in their cubic crystal structures predict a high degree of spin polarization of 86% and 82%, respectively. Figure 1(b) shows the calculated element- and spin- resolved density of states for CoFeVGe. These results indicate that Co1.25Fe0.75VGe has a potential for near room temperature spintronic applications.
This research is supported by the National Science Foundation (NSF) under Grant Numbers 2003828 and 2003856 via DMR and EPSCoR. 

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Structural and Magnetic Properties of CoFeVGe: Experiment and Theory

Spin transfer torque magnetic random access memory (STT-MRAM) shows great advantages for computing-in-memory (CIM) [1][2]. Time-domain (TD) in-MRAM computing can be implemented with unlimited signal accumulation and low power consumption characteristics thanks to its low precision [3]. In this paper, we propose a novel TD-CIM topology that converts bit-line (BL) voltage to time delay.
Fig.1 (a) shows the structure of proposed STT-MRAM for TD-CIM. Fig.1 (b) illustrates the proposed AND/OR/Full-Adder (FA) Boolean logic circuit, with one transistor-one magnetic tunnel junction (1T-1MTJ) bit-cell. RP/RAP (parallel and anti-parallel magneto-resistance) is with data ‘0’/‘1’. During computation mode, word-line (WL) activates two bit-cell within one row. The calculation-line (CL) generates differential VBL according to the state of bit-cell. Current starved inverters (CSI) circuit is used to convert the voltage of BL to time delay [4]. The inverter chains (REF0/REF1) generate delay to represent data ‘0’/1’ for FA logic, which is controlled by signal Cin. Time-to-Digital converter (TDC) converts CSI outputs from time domain to digital domain. The inverter chains generate reference delay for AND/OR/FA logic. CSI outputs sample the reference delay by D-flip-flop (one flip-flop for AND/OR, three flip-flops and one Multiplexer for FA).
The performance is analyzed with a 28-nm CMOS process and a MTJ compact model [5]. Fig.2 (a) demonstrates the simulated 500 runs Monte-Carlo analysis of CSI outputs under different cases. Results show the successfully distinguished CSI accumulation. The power consumption of AND/OR and FA is 7.89-μW and 14.1-μW at nominal 0.9V supply (see Fig. 2(b)). Fig.2 (c) shows the computation accuracy of AND/OR/FA logic in varied tunnel magnetoresistance ratio (TMR) with different data cases. When TMR=200%, 94.2% to 100% computation accuracy can be obtained, whereas the accuracy is deteriorated when TMR equals to 125%. 
**References** [1] M. Wang et al., Nature Communications, vol. 9, p. 671 (2018).
[2] X. Fong et al., IEEE Trans. on Very Large Scale Integration (VLSI) Systems, vol. 22, pp. 384–395 (2014).
[3] P. -C. Wu et al., IEEE International Solid- State Circuits Conference (ISSCC), pp. 1-3 (2022).
[4] Q. -K. Trinh et al., IEEE Trans. on Circuits and Systems I: Regular Papers, vol. 65, no. 10, pp. 3338-3348 (2018).
[5] Y. Wang et al., IEEE Trans. on Electron Devices, vol. 63, pp. 1762-1767 (2016). 

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Time domain Computing for Boolean Logic using STT

Magnetism in two-dimensional (2D) van der Waals (vdW) materials has emerged as a new paradigm enunciating new condensed matter phenomena, bearing potential for application in future spintronic and quantum computing devices (1,2). Among 2D vdW ferromagnets (FMs), metallic Fe3GeTe2 (FGT) is interesting owing to its high Curie temperature, uniaxial magnetic anisotropy, existence of unusual magnetic ground state. An understanding of factors responsible for unconventional magnetism and associated magnetoresistive manifestations has remained elusive. Here, we clarify the underlying physics responsible for nontrivial ground state and demonstrate tuning of emergent properties by substitution at magnetic (Fe) or nonmagnetic (Ge) sites in 2D vdW FGT.
High quality single-crystalline FGT, (Fe1-xCox)3GeTe2, Fe3(Ge1-xAsx)Te2 , (0 ≤ x ≤ 1) were grown by chemical vapor transport method. Magnetotransport measurements under H || c-axis result in sizeable anomalous Hall effect, arising from topological nodal lines in the band structure. Interestingly, transverse resistivity under H ⊥ c-axis result in unconventional magnetoresistive behavior with prominent cusp-like feature (Fig. 1) (3,4). Concomitant magneto-optical imaging indicates emergent skyrmion lattice-like structure, size varying with doping and angular magnetotransport confirms their 2D nature. Separation of magnetoresistive responses indicates dominant unconventional emergent Hall effect (3,4), tunable with magnetic or non-magnetic doping (Fig. 2), significantly larger than in other vdW, skyrmion-hosting materials (5-7). Our results deepen understanding of emergent responses from complicated spin textures prospective for topological magnetism and non-collinear spin texture-based spintronic devices. 

RRC acknowledges DST for financial support (DST/INSPIRE/04/2018/001755). We thank H. Ohno for discussions. This work is partly supported by RIEC Cooperative Research Project. 

**References:** 
(1) B. Huang et al., Nature 546, 270 (2017). 
(2) K. S. Burch et al., Nature 563, 47 (2018). 
(3) R. Roy Chowdhury et al., Sci. Rep. 11, 14121 (2021). 
(4) R. Roy Chowdhury et al., Phys. Rev. Mater. 6, 014002 (2022). 
(5) Y. Wang et al., Phys. Rev. B. 96, 134428 (pp 1-6) (2017). 
(6) S. Seki et al., Science 336, 198-201 (2012). 
(7) N. Kanazawa et al., Adv. Mater. 29, 1603227 (2017). 

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Unconventional Emergent Hall Effect Phenomena and its Modification In a van der Waals Ferromagnet Fe3GeTe2

Spin waves (SW) possess specific properties that make them well-suited for microwave applications. Very often these applications rely on magnetic bodies where large populations of coherently pumped spin waves share a common space with their less coherent biproducts and with the thermal populations of spin waves. It is thus of interest to develop experimental techniques able of measuring spin waves in broad frequency intervals with a large dynamic range, ideally from the floor of the thermal population of spin waves up to the regime of large amplitudes of magnetization precession.
We have studied how a population of spin waves can be characterized from the analysis of the electrical microwave noise delivered by an inductive antenna placed in its vicinity [1]. The measurements are conducted on a synthetic antiferromagnetic thin stripe covered by a micron-sized antenna that feeds a spectrum analyzer after amplification. The antenna noise contains two contributions.
(i) The population of incoherent spin waves generates a fluctuating field that is sensed by the antenna: this is the “magnon noise.”
(ii) The antenna noise also contains the contribution of the electronic fluctuations: the Johnson-Nyquist noise. The latter depends on all impedances within the measurement circuit, which includes the antenna self-inductance. As a result, the electronic noise contains information about the magnetic susceptibility of the stripe, though it does not inform on the absolute amplitude of the magnetic fluctuations.

For micrometer-sized systems at thermal equilibrium, the electronic noise dominates and can account for the measured entire noise (see Figure 1) ; in this case the pure magnon noise cannot be determined. If in contrast the spin wave bath is not at thermal equilibrium with the measurement circuit, and if the spin wave population can be changed then one could measure a mode-resolved effective magnon temperature provided specific precautions are implemented. 
**References** [1] T. Devolder et al., Phys. Rev. B 105, 214404 (2022) 
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Measuring a Population of Spin Waves from the Electrical Noise of an Inductively Coupled Antenna

The work presented in this research is aimed at development of a novel absolute encoding method using De-Bruijn sequence with Hall-effect sensors to enable coding pattern of rotary encoders not limited to axial direction or to a specific disc size. This coding pattern resolves problem of repeated coding at the junction of a rotary encoder through creation of mathematical models and permutations of different sizes of sub-array. Based on the De-Bruijn sequence theory, the length of sub-array controls the number of Hall-effect sensing elements represented by n as illustrated in Figure 1, of which elements are linearly arranged on the sensing head. The proposed firmware of the measuring presets specific gates for the sensing elements with various limitations to distinguish certain codes on the pattern without misjudgment when external magnetic field changes. Through calibrated experiments, it was found and validated that when the sequence was constituted by a string of codes with high symbol, which is denoted as k, the gate value could determine the correctness of the absolute position. When the measurement system structure operates at a constant moving speed, the output data from the A, B, C and D sensing elements as shown in Figure 2 can be discriminated synchronously. The results obtained in this research demonstrate two things. Firstly, the absolute position can be identified by lookup table corresponding to the specific code with 1 mm resolution. Secondly, the De-Bruijn code can be regarded as a circular code to avoid misjudgments that commonly observed with traditional methods. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f64b43f2443dc02ed69ecfdc55e97751.png) 
Schematic of a measuring system consisting of a sensor head and a magnetic medium with a De-Bruijn code pattern. 
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Experimental results with four channels of the analog signal. The symbol detected in each channel can be treated as a subsequence.

High Symbol De Bruijn Code as an Absolute Pattern for Rotary Magnetic Encoders of Arbitrary Size

The areal recording density of hard disk drives has a potential to reach 4 Tb/in2 with the heat-assisted magnetic recording (HAMR) technology [1]. So far, the best candidate for HAMR media is FePt nanogranular thin films with the L10 ordered structure. To improve the recording density and reduce the jitter noise, the bimodal grain size distribution and nanostructural defects, that are unavoidable in actual FePt films, must be suppressed. Grains with {111} twinning variants, [200] misoriented grains, and disordered grains with negligible magnetic anisotropy constants (K = 0) can be listed among the detrimental defects. Evaluation of their volume fractions, V111, V200 and VK=0 respectively, is of a vital interest. A new micromagnetic characterization of FePt nanogranular media is proposed in this work [2]. We developed a method of constructing finite element models of FePt granular media based on high-resolution transmission electron microscopy (TEM) images taken from top and side views of the films (Fig. 1). Using the TEM image based model, an accurate micromagnetic approximation of the out-of-plane hysteresis loops was achieved for MgO(6 nm)/FePt-BN(1 nm)/FePt-(C,SiO2)(7 nm) thin films as shown in Fig. 2. It yielded parameters of uniaxial magnetic anisotropy (mean magnetic anisotropy constant K, its standard deviation, distortion of easy magnetization axes) and the volume fractions of the defects. Evaluated V111 and V200 were in excellent agreement with those determined by synchrotron XRD. After such an experimental validation, we collected a dataset of demagnetization curves by micromagnetic simulations upon different parameters of magnetic anisotropy and volume fractions of defects, then a neural network was trained to predict these parameters and use them as an initial set for the micromagnetic approximation that speeded up the approach significantly [3]. Thus, the developed TEM image based micromagnetic simulations assisted by machine learning can boost optimization of FePt HAMR media linking its nanostructural features to magnetic properties. 
**References** 
[1] K. Hono et al., MRS Bull. 43 (2018) 93. 
[2] A. Bolyachkin et al., Acta Mater. 227 (2022) 117744. 
[3] E. Dengina et al., Scripta Mater. 218 (2022) 114797. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/ac606ea50887649d903f8f32221d1c31.png) 
Fig. 1. Finite element model of FePt granular media constructed based on TEM images. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/cf38cb194d3e886d75ada05fa2dc4ba6.png) 
Fig. 2. Micromagnetic approximation of an experimental out-of-plane hysteresis loop.

Machine learning assisted micromagnetic approximation for FePt HAMR media

While CoPt and FePt magnets have high magnetic anisotropy (MAE) when chemically ordered into L10 structures, their components’ high criticality calls for a search for more sustainable systems. Ab initio modelling confirms the pivotal role of the tetragonal order for this useful permanent magnetic property [1]. L10-FeNi, found in meteoritic, tetrataenite samples, also has significant uniaxial anisotropy [2,3]. We report integrated modelling of ternary FeNi-based alloys of both the propensity for L10 order and the MAE. We study Fe50Ni40X10 alloys (X = Pt, Pd, Al, Ti, Mo, Nb, Ta, W). Crucially, to guide material design, our modelling accounts for the physics that the same electrons which produce the MAE also glue the atoms into their places in the crystal structure. There are 3 steps: 1. The MAE is calculated for an ideal (prescribed) ferromagnetic (FM) L10 ordered material (top figure) - alternating Fe and Ni80X20 layers. These values, per formula unit (FU), are shown in the 5th column (col) of the table. 2. The atomic, short-range order (ASRO) in a high temperature, paramagnetic (PM), f.c.c. solid solution, Fe50Ni40X10 is calculated [4] to learn whether L10 order forms readily (col 2) and to determine the compositions of the alternating layers (col 3) if it does (lower figure). 3. The MAE of the ensuing L10 alloys are calculated (col 4). FM L10 Fe-Ni80Pt20 has a large MAE of 0.39 meV/FU but Fe-Ni80Al20’s value of 0.23meV/FU is significant and twice that of L10-FeNi. The chemical ordering, however, supported by the electrons of the materials, does not lead to these desired atomic arrangements and only the Pt, Pd, Al-doped alloys adopt any L10 order with sharply reduced MAEs (col 4). Comparison of the ASRO in PM and FM Fe50Ni50 solid solutions shows a way to circumvent this issue and explain the L10-order in meteoritic FeNi samples. Spin-polarized electronic structure is paramount to establish L10 order - PM Fe50Ni50 has no propensity whatsoever to adopt this order in sharp contrast to the alloy in a FM state which is predicted to order into the L10 structure below 670K [5]. 
[Research performed in part under the auspices of the U.S. Department of Energy, Office of Science under Award Number DE SC0022168.] 
**References:** [1] J. B. Staunton et al., https://doi.org/10.1103/PhysRevB.74.144411 
[2] R. S. Clarke and E. R. D. Scott, American Mineralogist 65, no. 7-8 (1980): 624-630. 
[3] N. Maat et al. Acta Materialia. 2020 Sep 1;196:776 
[4] C. D. Woodgate and J. B. Staunton, https://doi.org/10.1103/PhysRevB.105.115124 
[5] V. Crisan et al., https://doi.org/10.1103/PhysRevB.66.014416 

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Figure 1 
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Figure 2

Integrated ab initio computational modelling of magnetic anisotropy and L10 order in non critical transition metal magnets

Fabrication of nanostructures can be categorized into top-down and bottom-up approaches. The top-down approach uses various kinds of lithography, which has
unprecedented accuracy and controllability, yet requires sophisticated equipment and expensive operating costs. On the other hand, the bottom-up approaches are cost-efficient and do not
rely on sophisticated facilities. However, it is determined by self-organization, which lacks strict repeatability and spatial homogeneity over a long distance. Here, we report an
unprecedented electrochemical growth of ordered metallic nanowire arrays from an ultrathin electrolyte layer, which is achieved by solidifying the electrolyte solution below the freezing
temperature. We apply the electric voltage pulses across two straight, parallel electrodes. The thickness of the electrodeposit is instantaneously tunable by the applied electric pulses,
leading to parallel ridges on webbed film without using any template. An array of metallic nanowires with desired separation and width determined by the applied pulses is formed on the
substrate with arbitrary surface patterns by etching away the webbed film thereafter. Unlike conventional nanowires growing along their longitudinal axial direction, here the whole
nanowire simultaneously develops in the direction perpendicular to the wire axis. Besides, the nanowires can be fabricated on a surface with any topography, including silicon grating with
a high–aspect ratio surface pattern. This work[1] demonstrates a previously unrecognized fabrication strategy that bridges the gap of top-down lithography and bottom-up self-organization
in making ordered metallic nanowire arrays over a large area with low cost. 

**References:** 

[1]. F. Chen, Z. Yang, J.-N. Li, F. Jia, F. Wang, D. Zhao, R.-W. Peng, M. Wang, Science Advances., Vol 8, p. eabk0180 (2022)

Formation of magnetic nanowire arrays by cooperative lateral growth

Complex perovskite oxides exhibit a rich spectrum of functional responses, including magnetism, ferroelectricity, highly correlated electron behavior, superconductivity, etc. The basic materials physics of such materials provide the ideal playground for interdisciplinary scientific exploration with an eye towards real applications. Over the past decade the oxide community has been exploring the science of such materials as crystals and in thin film form by creating epitaxial heterostructures and nanostructures. Among the large number of materials systems, there exists a small set of materials which exhibit multiple order parameters; these are known as multiferroics, particularly, the coexistence of ferroelectricity and some form of ordered magnetism (typically antiferromagnetism). The scientific community has been able to demonstrate electric field control of both antiferromagnetism and ferromagnetism at room temperature. In parallel, there are some very intriguing new developments in SOT based manipulation of magnets. Particularly, the role of epitaxy and electronically perfect interfaces has been shown to significantly impact the spin-to-charge conversion (or vice versa). Under funding from the US. Department of Energy and the SRC-DARPA-JUMP funded ASCENT Center, current work is focused on ultralow energy (1 attoJoule/operation) electric field manipulation of magnetism with both voltage and current, as the backbone for the next generation of ultralow power electronics. We are exploring many pathways to get to this goal. In this talk, I will describe our progress to date on this exciting possibility. The talk will conclude with a summary of where the future research is going.

Voltage & Current Controlled Nanomagnetism For Memory and Logic

The non-volatile spin-orbit torque (SOT)-MRAM is emerging as key enabling low-power technologies, which are expected to spread over large markets from embedded memories to the Internet of Things. Concurrently, the development and performances of devices based on two-dimensional (2D) heterostructures bring ultra-compact multilayers with unprecedented material-engineering capabilities. We first discuss an overview of the current developments and challenges in the field, and then outline the opportunities which can arise by implementing 2D materials into SOT-MRAM technologies (Fig. 1) [1]. We highlight the fundamental properties of atomically smooth interfaces, the reduced material intermixing, the crystal symmetries, and the proximity effects as the key drivers for possibly disruptive improvements for SOT-MRAM at advanced technology nodes.
Among various spin source materials, the 2D van der Waals topological materials such as topological insulators and Weyl semimetals, have attracted considerable attention because of their non-trivial band structures with strong spin-orbit coupling and expected giant SOT. Therefore, topological materials are regarded as promising candidates for future energy-efficient SOT device applications. However, some related physical, material, and device issues still need to be addressed. We review recent advances regarding the charge-to-spin conversion and SOT-driven magnetization switching based on the emerging 2D van der Waals materials, with an emphasis on topological insulators and Weyl semimetals, and present our perspective on practical SOT device applications using this emerging family of quantum van der Waals materials. Specifically, we show our SOT-related experimental advances that have been made in the topological material/ferromagnet heterostructures and devices, involving the giant SOT characterizations, interfacial Edelstein–Rashba effect, Dzyaloshinskii–Moriya interaction (DMI) and interfacial spin transmission. Furthermore, we highlight the highly efficient SOT-driven magnetization switching at room temperature based on 2D van der Waals heterostructures, along with the wafer-scale films prepared with industry-compatible techniques, such as molecular beam epitaxy, magnetron sputtering, and chemical vapor deposition. We anticipate that these studies will deepen the understanding of SOT on 2D van der Waals heterostructures and guide the design and applications of high-performance 2D material-based SOT devices. 

**References:** 

[1] H. Yang et al., “Two-dimensional Materials Prospects for Non-volatile Spintronic Memories” Nature 606, 663-673 (2022) 

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Angular dependent magnetoresistance and magnetic soliton lattice in Cr1/3NbS2

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