Dzyaloshinskii-Moriya Interaction Research Articles

A radial basis function-finite difference method for solving Landau–Lifshitz–Gilbert equation including Dzyaloshinskii-Moriya interaction

This paper investigates a numerical method for solving the two-dimensional Landau–Lifshitz–Gilbert (LLG) equation, governing the dynamics of the magnetization in ferromagnetic materials. Specifically, we incorporate the Dzyaloshinskii–Moriya interaction into the LLG equation—a crucial factor for the creation and stabilization of magnetic skyrmions. We propose a local meshless method that utilizes radial basis function-finite difference (RBF-FD) for spatial discretization and the Crank–Nicolson scheme for temporal discretization, along with an extrapolation technique to handle the nonlinear terms. We demonstrate the method’s accuracy, efficiency, and adaptability through numerical tests on domains of various shapes, showcasing its practical utility in simulating real-world magnetic phenomena and advanced materials.

Stability and evolution of skyrmionium and skyrmions in a spherical shell

The study of magnetic structures, particularly those with curved geometries such as spherical shells, has obtained significant interest due to their potential applications in data storage, spintronics, and other advanced technologies. However, the effects of material parameters, geometric dimensions, and magnetic fields on the equilibrium and induced behaviors of skyrmions remain largely unresolved. Here, based on micromagnetic simulations, we firstly investigate the influence of spherical shell dimensions, magnetic anisotropy, exchange interaction, and Dzyaloshinskii–Moriya interaction on the magnetic states of spherical shells. We find that curvature effects become more pronounced with increasing thickness and decreasing radius, providing evidence for the role of curvature-induced DMI-like interactions in skyrmion formation. Additionally, we observe that applying a magnetic field to the spherical shell induces behaviors similar to those in disks, including the topological transition between skyrmionium and skyrmion states, the annihilation of skyrmions, and polarity reversal. Our study aims to advance the understanding of magnetic phenomena in curved geometries and contribute to the development of novel magnetic devices.

Rich magnon topology in triangular lattice magnets

The two-dimensional magnet has been an emerging and rapidly growing field. The nontrivial topological phenomenon in these materials is an attracting subject. Yet, the realization of such magnets exhibiting topological magnons remains a challenge. Here, employing the linear spin-wave theory and the first-principles calculations, we propose that variety of topological phases exist in the triangular ferromagnet. These include magnon Chern insulators and high-order topological insulators. Interestingly, these topological states can coexist within a certain parameter space, leading to a hybrid topological state. We propose that these topological phases can be realized via atomic substitutions inMnSe2orMnTe2single-layers. The following detailed analysis suggests that non-uniform Dzyaloshinsky-Moriya interactions are crucial in achieving topological magnons. Our work unveil a unique approach to obtaining non-trivial topological magnons in two-dimensional materials.

Control of chiral damping in magnetic trilayers using He+ ion irradiation

In the forefront of spintronic advancements, structures with strong perpendicular magnetic anisotropy (PMA) such as Pt/Co/Pt are essential for the miniaturization and performance enhancement of high-density magnetic storage technologies. The robust PMA characteristic of these systems facilitates the development of scalable spintronic devices, crucial for next-generation magnetic memory applications. This study investigates the interplay between PMA and the Dzyaloshinskii-Moriya interaction (DMI)—an antisymmetric exchange interaction prevalent in non-centrosymmetric magnetic systems—and its dissipative counterpart, chiral damping. While chiral damping arises from the same broken inversion symmetry as DMI, it typically introduces an additional energy dissipation channel, reducing device efficiency. Our research examines the effects of controlled helium ion (He+) irradiation on a Pt/Co/Pt system. We find that ion beam irradiation enhances interfacial intermixing, which correlates with a decrease in PMA. However, domain wall velocity measurements indicate a concurrent reduction in both DMI and chiral damping, along with enhanced velocities as irradiation fluence increases. These observations suggest that ion beam irradiation can be judiciously applied to achieve a balance between lower DMI, chiral damping, and reasonable PMA, thereby optimizing the system for improved device performance.

Antiferro skyrmion crystals consisting of skyrmions and anti-skyrmions on a bilayer square lattice

An antiferro-type skyrmion crystal consisting of skyrmions with a negative topological charge and antiskyrmions with a positive topological charge manifests itself in its peculiar topological magnetism. We theoretically investigate the emergence of such an antiferro-type skyrmion crystal, where the topological charge exists in each sublattice but vanishes in the whole system. By performing the simulated annealing for an effective spin model with competing exchange interactions and staggered Dzyaloshinskii-Moriya interaction in momentum space on a bilayer square lattice, we find that the synergy between the antiferromagnetic interlayer exchange interaction and high-harmonic wave-vector interaction in addition to the staggered Dzyaloshinskii-Moriya interaction results in the antiferro-type skyrmion crystal in an external magnetic field. We show that the antiferro-type skyrmion crystal turns into the ferro-type skyrmion crystal with the same topological charge for both layers when the magnitude of the external magnetic field is varied. We also demonstrate that the competing interactions between ordering wave-vector channels and their high-harmonic wave-vector channels are essential in stabilizing the antiferro-type skyrmion crystal. Our results provide important ingredients to realize the antiferro-type skyrmion crystal by the external magnetic field, which can be utilized for low-power and high-speed spintronic devices based on antiferromagnetic materials.

Valley modulation and topological phase transition in staggered kagome ferromagnets

Abstract Owing to their charge-free property, magnons are highly promising for achieving dissipationless transport without Joule heating, and are thus potentially applicable to energy-efficient devices. Here, we investigate valley magnons and associated valley modulations in a kagome ferromagnetic lattice with staggered exchange interaction and Dzyaloshinskii–Moriya interaction. The staggered exchange interaction breaks the spatial inversion symmetry, leading to a valley magnon Hall effect. With nonzero Dzyaloshinskii–Moriya interaction in a staggered kagome lattice, the magnon Hall effect can be observed from only one valley. Moreover, reversing the Dzyaloshinskii–Moriya interaction (D → −D) and exchanging J 1 and J 2 (J 1 ↔ J 2) can also regulate the position of the unequal valleys. With increasing Dzyaloshinskii–Moriya interaction, a series of topological phase transitions appear when two bands come to touch and split at the valleys. The valley Hall effect and topological phase transitions observed in kagome magnon lattices can be realized in thin films of insulating ferromagnets such as Lu2V2O7, and will extend the basis for magnonics applications in the future.

Dzyaloshinskii-Moriya interaction transistor with magnetization manipulated by electric field

Dzyaloshinskii-Moriya interaction transistor with magnetization manipulated by electric field

Quantum skyrmion dynamics studied by neural network quantum states

We study the dynamics of quantum skyrmions under a magnetic field gradient using neural network quantum states. First, we obtain a quantum skyrmion lattice ground state using variational Monte Carlo with a restricted Boltzmann machine as the variational ansatz for a quantum Heisenberg model with a Dzyaloshinskii-Moriya interaction. Then, using the time-dependent variational principle, we study the real-time evolution of quantum skyrmions after a Hamiltonian quench with an inhomogeneous external magnetic field. We show that field gradients are an effective way of manipulating and moving quantum skyrmions. Furthermore, we demonstrate that quantum skyrmions can decay when interacting with each other. This work shows that neural network quantum states offer a promising way of studying the real-time evolution of quantum magnetic systems that are outside the realm of exact diagonalization. Published by the American Physical Society 2024

Evolution of static and dynamic magnetic properties of Re/Co/Pt and Pt/Co/Re trilayers with enhanced Dzyaloshinskii-Moriya interaction

The influence of Re layer insertion either at the bottom or top interface of epitaxially grown Pt/Co/Pt heterostructures on their static and dynamic magnetic properties is discussed in terms of their crystalline structure. Magnetic properties were studied as a function of both Re and Co layer thicknesses (dRe and dCo, respectively) in the matrix-like samples with a double-wedge structure, in which the layer thickness gradients were oriented orthogonally. The comprehensive investigations of the changes in coercivity, perpendicular magnetic anisotropy, spin reorientation transition, interfacial Dzyaloshinskii-Moriya interaction (iDMI) and spin wave damping are reported. Two different magnetic phases depending on the Co layer thickness with volume anisotropies (determined without demagnetization term) of KV∼0.25 (low) and KV∼0.75 MJ/m3 (high) were observed. The relation between these phases depends on the stack sequence and thickness of Re inserted layer. For dRe = 0.2 ÷ 0.7 nm deposited as the bottom interface, dCo induced transition at dtr ∼ 2 nm from low to high volume anisotropy phases was observed. Low and high volume anisotropy phases are associated to Co fcc and hcp structural phases. The insertion of half atomic layer of Re had no influence on surface anisotropy but significantly enhanced iDMI above 1 pJ/m and reduced spin wave damping.

Electric field induced thermal Hall effect of triplons in the quantum dimer magnets XCuCl3 ( X=Tl,K )

We theoretically propose the electric field induced thermal Hall effect of triplons in the quantum dimer magnets XCuCl3 (X=Tl,K), which exhibit ferroelectricity in the Bose-Einstein condensation phase of triplons. The interplay between ferroelectricity and magnetism in these materials leads to the magnetoelectric effect, i.e., an electric-field induced Dzyaloshinskii-Moriya (DM) interaction between spins on the same dimer. We argue that this intradimer DM interaction breaks the symmetry of the system in the absence of an electric field and gives rise to the thermal Hall effect, which can be detected in experimentally accessible electric and magnetic fields. We also show that the thermal Hall effect can be controlled by changing the strength or direction of the electric field. Published by the American Physical Society 2024

Metrological non-classical correlations and quantum coherence in hybrid (1/2,1) system under decoherence channels

Abstract Our research focuses on the interplay between thermal noise and decoherence channels on quantum coherence and nonclassical correlations in a hybrid ( 1 / 2 , 1 ) Heisenberg model. This hybrid system integrates the Dzyaloshinsky–Moriya interaction (DMI) and operates under the influence of an external magnetic field. We use local quantum Fisher information (LQFI) for correlation estimation and relative entropy of coherence for coherence measurement in the considered system. Our investigation encompasses various parameters of the hybrid system, the strength of the DMI and the intensity of the external magnetic field. Our findings underscore that elevated temperature compromises both nonclassical correlations and coherence. On the other hand, the robustness of the DMI mitigates the impact of thermal noise on quantum Fisher information correlations and relative entropy of coherence in the hybrid system. Additionally, we inspect the impact of decohering channels-specifically, dephasing, phase flip, and bit- and trit-flip channels-on thermal coherence and quantum correlations. The introduction of various decoherence processes into the hybrid qubit-qutrit system leads to a competition with thermal fluctuations, thereby giving rise to out-of-equilibrium states. Our results indicate that as the decoherence strength parameter (p) increases, both LQFI and relative entropy of coherence exhibit similar behaviors in the dephasing and phase flip channels. These resources gradually diminish, eventually disappearing entirely at p = 1. In the context of the bit- and trit-flip channels, quantum coherence displays notable distinctions compared to what is observed under dephasing and phase flip channels, revealing that coherence can be preserved if the DMI is strong and the intensity of the external magnetic field is reduced. These findings are important since it is crucial to first understand the decoherence process, arising from the interaction with the environment, and then to find ways to hinder this decoherence in order to avoid the complete loss of the quantum resources necessary to quantum information processing.

Spin photo-currents in antiferromagnets with Dzyaloshinskii–Moriya interactions

Spin photo-currents in antiferromagnets with Dzyaloshinskii–Moriya interactions

Structural, magnetic, optical and electronic properties of Gd2NiIrO6

Polycrystalline Gd2NiIrO6 double perovskite compound was synthesized by the solid-state route. Rietveld refinement of the X-ray diffraction pattern revealed that the compound was crystallized in a monoclinic structure with P21/n space group (IUCr. No. 14). The scanning electron micrograph showed that the grains were spherical and well distributed with an average grain size of around 1 μm. The temperature-dependent magnetic measurements showed magnetic transitions at 165 K and 149 K in the low-temperature region. Below the transition temperatures, weak ferromagnetism was evidenced by field-dependent magnetization measurements. Exchange bias effects were observed which were driven by Dzyaloshinsky–Moriya interactions in the compound. The UV–visible measurement evidenced that the compound had an optical band gap of 1.8 eV. The electronic structure calculations using the DFT + U method revealed that Gd2NiIrO6 compound exhibited a bandgap only when on-site correlations for the d-states were included, and the calculation showed that the AF1 configuration was energetically favourable.

Eliminating Skyrmion Hall Effect in Ferromagnetic Skyrmions.

Skyrmion Hall effect (SkHE) remains an obstacle for the application of magnetic skyrmions. While methods have been established to cancel or compensate SkHE in artificial antiferromagnets and ferrimagnets, eliminating intrinsic SkHE in ferromagnets is still a big challenge. Here, we propose a strategy to eliminate SkHE by intercalating nonmagnetic elements into van der Waals bilayer ferromagnets featuring in-plane ferromagnetism. The in-plane magnetism, along with a delicate balance among exchange interactions, Dzyaloshinskii-Moriya interactions (DMI), and magnetocrystalline anisotropy, creates interlayer bimerons/quadmerons, whose polarity can be controlled by DMI. Opposite DMI in the upper and lower layers results in opposite polarity and topological charge number Q-locking of topological spin texture, therefore, eliminating the SkHE. By intercalating Sr (Ba) in bilayer VSe2, we identify ten topological magnetic structures with zero topological charge number. Furthermore, we present a phase diagram illustrating diverse magnetic configurations achievable within the bimagnetic atomic layer, offering valuable guidance for future investigations.

High-topological-number skyrmions with tunable diameters in two-dimensional frustrated J1−J2 magnets

Skyrmions are intriguing quasiparticles in the field of condensed matter due to their unique physics and promising applications in spintronic devices. However, despite abundant studies on skyrmions with a topological charge of Q = 1, there have been only few on those with higher Q (≥2) due to their intrinsic instability in Dzyaloshinskii–Moriya interaction (DMI) systems. In this work, applying the frustrated J1−J2 Heisenberg spin model, we investigate the stability of high-Q skyrmions and the manipulation of their diameters in a hexagonal close-packed lattice through atomistic simulations and first-principles calculations. First, three spin textures, called spiral, skyrmion, and ferromagnetic, are identified by varying (J1, J2), and it is shown that skyrmions with higher Q can occupy a wider range of (J1, J2) values. The diameter of the skyrmions can then be finely tuned using the frustration strength (|J2/J1|), the single-ion anisotropy (K), and an external magnetic field (B). As B increases, the high-Q skyrmions split into skyrmions with smaller Q and can be annihilated by a larger B. Furthermore, we find that the CoCl2 monolayer satisfies the criteria for a frustrated J1−J2 magnet, and its magnetic behaviors align with the aforementioned conclusions. In addition, high-Q skyrmions are identified in the CoCl2 monolayer, and the corresponding energy barriers for skyrmion collapse are investigated. Our findings pave the way for prospective spintronic applications based on high-Q and nanoscale skyrmionic textures.

Room temperature skyrmions in Pt/Co/Gd multilayers and their non-volatile electric-field creation in multiferroic heterostructure

This study delves into the formation and control of magnetic skyrmions within a Pt/Co/Gd multilayer system. By systematically varying the thickness of the Co layer, we observe the emergence of Néel-type skyrmions, characterized by confined magnetization curls with Lorentz transmission electron microscopy. The interplay between magnetic anisotropy, Dzyaloshinskii–Moriya interaction, and antiferromagnetic coupling at material interfaces is investigated to understand the stability and manipulation of these fascinating spin configurations. Additionally, we explore the impact of an external electric field on skyrmion generation, demonstrating a pathway for their controlled creation. The observed electric-field control of skyrmions offers a promising approach to achieving non-volatile magnetic states with low power consumption and negligible Joule heating. These findings hold great potential for advancing spintronics and magneto-electric devices, enabling modulation of skyrmions for information storage and processing applications.

Observation of competing interactions and field-induced ferromagnetism in noncentrosymmetric cubic Nd3Te4 lattice

Unconventional magnetism is key to advancement in a variety of spintronic applications and thus needs to be explored in new materials. Here, we report the in-depth magnetic studies of noncentrosymmetric Nd3Te4 and findings support the existence of Dzyaloshinskii-Moriya interaction in addition to symmetric exchange interaction among the moments. The large magnetic irreversibility with negative magnetization in M(T) data and associated first-order magnetic transition in isothermal magnetization data suggest the competing interactions resulting in multiple magnetic phases. The gradual evolution of magnetic texture has been probed by changes in the magnetization entropy having interesting characteristics like the inverse magnetocaloric effect. Most importantly, we have probed the existing nontrivial magnetic phase under a low applied magnetic field by ac-χ(T, H) and dc magnetization (M − H) data, having the same critical field in both measurements. The existence of multiple magnetic phases which are interconnected through first-order field-induced magnetic phase transitions have been probed at low field. The transition from paramagnetic to field-induced state for larger applied fields follows a second-order.

Characterizing quantum correlations dynamics in Heisenberg system with Dzyaloshinskii–Moriya interaction

Characterizing quantum correlations dynamics in Heisenberg system with Dzyaloshinskii–Moriya interaction

The role of interfacial Dzyaloshinskii–Moriya interaction in different heavy metal-based perpendicular magnetic systems and its application in spintronic devices

The interfacial Dzyaloshinskii–Moriya interaction (DMI) acting as an essential source to stabilize spin textures in ferromagnetic ultrathin films has revealed its significant role in spin–orbit torque (SOT)-driven magnetic switching. Based on a convincing homochiral Néel domain wall model, the in-plane (IP) magnetic field associated with the DMI effect has been confirmed as an essential prerequisite for deterministic SOT-driven switching. Although the presence of the IP field is required, the impact of IP field magnitude combined with the DMI effect on SOT-driven switching in different heavy metals (HMs) has never been considered together. In this research, SOT-induced switching under various IP fields in Pt, W, or Ta/CoFeB/MgO systems has been studied. The results show that the critical threshold current IC is almost independent of the IP field in the Pt-based structure; however, it significantly decreases with an increase in the IP field in the W- and Ta-based systems. Combining the derived DMI field and the magnetic domain nucleation, it is concluded that the significant difference in DMI fields and the domains' nucleating positions are the main reasons for the above phenomenon. Exploiting the distinct dependent properties of IC on the IP field, a six resistance state multilevel storage and five programmable spin logic gates are proposed and realized. This study provides insight into the special ability of the SOT effect modulated by the DMI, and also expands an effective way to construct spin-based devices based on this unique spintronic effect.

Tunable topological magnetism in superlattices of nonmagnetic B20 systems

We predict topological magnetic properties of B20 systems, that are organized in atomically thin multilayers. In particular, we focus on FeSi/CoSi and FeSi/FeGe superlattices with different numbers of layers and interface structures. We demonstrate that the absence of long-range magnetic order, previously observed in bulk FeSi and CoSi, is broken near the FeSi/CoSi interface, where a magnetic state with a nontrivial topological texture appears. Using the Heisenberg and Dzyaloshinskii-Moriya (DM) interactions calculated from first principles, we perform finite-temperature atomistic spin dynamics simulations for up to 2×106 spins to capture the complexity of noncollinear textures. Our simulations predict the formation of antiskyrmions in a [001]-oriented FeSi/CoSi multilayer, intermediate skyrmions in a [111]-oriented FeSi/CoSi system, and Bloch skyrmions in the FeSi/FeGe (001) system, with a size between 7 and 37 nm. These varieties of topological magnetic textures in the studied systems can be attributed to the complex asymmetric structure of the DM matrix, which is different from previously known magnetic materials. We demonstrate that through structural engineering both ferromagnetic and antiferromagnetic skyrmions can be stabilized, where the latter are especially appealing for applications due to the zero skyrmion Hall effect. The proposed B20 multilayers show a potential for further exploration and call for experimental confirmation. Published by the American Physical Society 2024