Effect Of Dzyaloshinskii-Moriya Interaction Research Articles

Feature of vortex core gyration affected by Dzyaloshinskii-Moriya interaction

The effects of Dzyaloshinskii-Moriya interaction (DMI) on vortex core gyration excited by an out-of-plane polarized current is investigated through micromagnetic simulation. The simulation results demonstrate that the DMI not only widens the current density range for gyration, but also greatly increases the frequency and velocity of gyration. On the premise that DMI is large enough and the vortex configurations can simultaneously be maintained, the stable gyration orbit changes from a circle, to a ring-like and to a bird-nest-like trajectory. Furthermore, by comparing the data of different-size nanodisks, it can be seen that the vortices in smaller and thinner disks can achieve higher velocity and larger amplitude gyration, while in larger and thicker disks, the magnetic vortices can obtain higher oscillation frequency. The conclusions in this research add to the potential applications of magnetic vortex in nano-oscillaors.

Theoretical study of the magnetic properties of BaNiF$$_4$$

In this article we study the magnetic properties of the BaNiF\(_4\) compound using ab-initio calculations and classical Monte-Carlo methods. We discuss the physical origin of the long range magnetic order. We show that the leading exchange interactions are those of a non-frustrated anisotropic two-dimensional Heisenberg system and that long range order and the experimentally observed preferential orientation of the magnetic moments along the \(\mathbf {b}\) axis appear when local single-ion anisotropy contributions are added at first order. We also show that a canting of the magnetic moments appears at second order and can be written as an effective Dzyaloshinskii-Moriya interaction.

Field-Free Deterministic Magnetization Switching Induced by Interlaced Spin-Orbit Torques.

Spin-orbit torque (SOT) magnetic random access memory is envisioned as an emerging nonvolatile memory due to its ultrahigh speed and low power consumption. The field-free switching scheme in SOT devices is of great interest to both academia and industry. Here, we propose a novel field-free deterministic magnetization switching scheme in a regular magnetic tunnel junction by using two currents sequentially passing interlaced paths, with less requirements of the manufacturing process or additional physical effects. The switching is bipolar since the final magnetization state depends on the combination of current paths. The functionality and robustness of the proposed scheme are validated through both macrospin and micromagnetic simulation. The influences of field-like torque and the Dzyaloshinskii-Moriya interaction effect are further researched. Our proposed scheme shows good scalability and is expected to realize novel digital logic and even computing-in-memory platforms.

Ferroelectricity and ferromagnetism in a VOI2 monolayer: Role of the Dzyaloshinskii-Moriya interaction

Multiferroics with intrinsic ferromagnetism and ferroelectricity are highly desired but rather rare, while most ferroelectric magnets are antiferromagnetic. A recent theoretical work [Phys. Rev. B {\bf 99}, 195434 (2019)] predicted that oxyhalides VO$X_2$ ($X$: halogen) monolayers are two-dimensional multiferroics by violating the empirical $d^0$ rule. Most interestingly, the member VOI$_2$ are predicted to exhibit spontaneous ferromagnetism and ferroelectricity. In this work, we extend the previous study on the structure and magnetism of VOI$_2$ monolayer by using density functional theory and Monte Carlo simulation. The presence of the heavy element iodine with a strong spin-orbit coupling leads an effective Dzyaloshinskii-Moriya interaction in the polar structure, which favors a short-period spiral a magnetic structure.. Another interesting result is that the on-site Coulomb interaction can strongly suppress the polar distortion thus leading to a ferromagnetic metallic state. Therefore, the VOI2 monolayer is either a ferroelectric insulator with spiral magnetism or a ferromagnetic metal, instead of a ferromagnetic ferroelectric system. Our study highlights the key physical role of the Dzyaloshinskii-Moriya interaction.

Domain-period method for determination of the energy of the Dzyaloshinskii-Moriya interaction in [Co/Pd(111)]5 superlattices

Determination of the energy of Dzyaloshinskii-Moriya interaction along with a definition of the basic magnetic characteristics in ferromagnetic/nonmagnetic multilayered systems are both required for the construction of a magnetic skyrmion recording medium. A method for estimating the energy of the effective Dzyaloshinskii-Moriya interaction which compared the periodicities of micromagnetically simulated and experimentally measured demagnetized domain structures was shown in a current paper. Symmetric epitaxial [Co/Pd(111)]5 superlattices with Co layers of varying thickness were used as the system for investigation. The structural and magnetic properties of epitaxial [Co(dCo)/Pd]5 superlattices with different Co layers thicknesses were comprehensively investigated. The dependence of the energy of effective Dzyaloshinskii-Moriya interaction on the thickness of the Co layers in the [Co(dCo)/Pd]5 multilayered structures was determined. The relationship between Dzyaloshinskii-Moriya interaction and asymmetry of the strains between the bottom Pd/Co and top Co/Pd interfaces was discussed. The simulation parameters and the demagnetization approach prior to measuring the magnetic structure influenced the obtained results. Necessity of setting all the layers in micromagnetic simulations was established. The significant influence of interlayer dipolar coupling on the periodicity of simulated labyrinth domain structures was also confirmed.

Influence of Dzyaloshinskii-Moriya interaction on the magnetic vortex gyration driven by a spin-polarized current

The effects of Dzyaloshinskii-Moriya interaction (DMI) on the magnetic vortex gyrations in a Permalloy nanodisk are investigated using micromagnetic simulation under the excitation of an out-of-plane spin-polarized current. It is found that spin-polarized current can drive the vortex to display two mode gyrations in the presence of DMI. Mode I gyration is like the conventional gyration studied in previous studies with the similar gyration radius, velocity and the eigenfrequency. However, the velocity of mode II gyration is about 2 times higher than that of mode I gyration, but with half gyration radius. And the eigenfrequency in mode II gyration is higher than that in mode I gyration by one order of magnitude. In addition, simulation calculations reveal that the magnetic vortex of these two mode gyrations can be triggered to gyration in shorter time compared with the conventional gyration.

Band topology, Hubbard model, Heisenberg model, and Dzyaloshinskii-Moriya interaction in twisted bilayer WSe2

We present a theoretical study of single-particle and many-body properties of twisted bilayer WSe$_2$. For single-particle physics, we calculate the band topological phase diagram and electron local density of states (LDOS), which are found to be correlated. By comparing our theoretical LDOS with those measured by scanning tunneling microscopy, we comment on the possible topological nature of the first moir\'e valence band. For many-body physics, we construct a generalized Hubbard model on a triangular lattice based on the calculated single-particle moir\'e bands. We show that a layer potential difference, arising, for example, from an applied electric field, can drastically change the non-interacting moir\'e bands, tune the spin-orbit coupling in the Hubbard model, control the charge excitation gap of the Mott insulator at half filling, and generate an effective Dzyaloshinskii-Moriya interaction in the effective Heisenberg model for the Mott insulator. Our theoretical results agree with transport experiments on the same system in several key aspects, and establish twisted bilayer WSe$_2$ as a highly tunable system for studying and simulating strongly correlated phenomena in the Hubbard model.

Effect of Dzyaloshinskii-Moriya interaction on magnetic vortex switching driven by radial spin waves

We theoretically investigate the radial-spin-wave induced magnetic vortex switching in the presence of Dzyaloshinskii-Moriya interaction (DMI). From micromagnetic simulations, we observe a circular-to-radial vortex phase transition by increasing the DMI strength. The radial spin-wave excitation spectrum for each magnetization configuration is analyzed, showing that the frequency of spin-wave mode with a given radial node number monotonically increases (decreases) with the DMI parameter of the radial (circular) vortex. Interestingly, we find that the DMI can significantly facilitate the polarity switching of the circular vortex driven by radial spin waves. Our work provides a new insight into the DMI effect on the vortex dynamics and is helpful for designing fast all-magnonic memory devices.

Current-induced effective Dzyaloshinskii-Moriya interaction and its Kondo enhancement in double quantum dot.

We studied the nonequilibrium transport of serially coupled double quantum dots connected to ferromagnetic electrodes. We demonstrated that the nonadiabatic part of the spin gauge field resulted in a current-induced Dzyaloshinskii-Moriya (DM) interaction effect in a double quantum dot and numerically confirmed this observation through the hierarchical equations of motion approach. We report that the spin current and the effective DM interaction are enhanced in the Kondo regime. We demonstrate that this enhancement occurs because the Kondo resonance, which is supposed to be suppressed by the local ferromagnetic exchange, is enhanced by the inter-dot coupling. This additional Kondo resonance channel increases the spin current. In addition, the impact of the spin-spin interaction and the Kondo effect on tunnel magnetoresistance is discussed. Our results offer a new approach for controlling the non-collinear spin interaction in double quantum dot devices.

Quantum pseudo-telepathy in spin systems: the magic square game under magnetic fields and the Dzyaloshinskii–Moriya interaction

The Dzyaloshinskii–Moriya (DM) interaction has been proved to excite entanglement of spin systems, enhancing the ability to realizing various quantum tasks such as teleportation. In this work we consider DM interaction—to the best of our knowledge for the first time—in quantum game theory. We study the winning probability of the magic square game played with the thermally entangled state of spin models under external magnetic fields and DM interaction. We analytically show that although DM interaction excites the entanglement of the system as expected, it surprisingly reduces the winning probability of the game, acting like temperature or magnetic fields, and also show that the effects of DM interaction and an inhomogeneous magnetic field on the winning probability are identical. In addition, we show that the XXZ model is considerably more robust than the XX model against destructive effects. Our results open up new insights for quantum information processing with spin systems.

Dzyaloshinskii-Moriya interaction in symmetric epitaxial [Co/Pd(111)]N superlattices with different numbers of Co/Pd bilayers

Heavy metal/ferromagnetic superlattices are of great interest since N\'eel skyrmions may be stabilized in them due to an interfacial Dzyaloshinskii-Moriya interaction even at room temperature. Here we report on evidence of the strong Dzyaloshinskii-Moriya interaction in symmetric epitaxial ${[\mathrm{Co}/\mathrm{Pd}(111)]}_{N}$ superlattices with high perpendicular magnetic anisotropy. The structural and magnetic properties of epitaxial ${[\mathrm{Co}/\mathrm{Pd}(111)]}_{N}$ superlattices were investigated dependent on the number of Co/Pd bilayers. Based on comparison of the periodicity of experimentally obtained demagnetized patterns and simulated magnetic structures, a strong increase of the effective Dzyaloshinskii-Moriya interaction constant with increase of the period $N$ of ${[\mathrm{Co}/\mathrm{Pd}(111)]}_{N}$ superlattices is established. The origin of Dzyaloshinskii-Moriya interaction and its behavior in the symmetric ${[\mathrm{Co}/\mathrm{Pd}(111)]}_{N}$ system is discussed.

Quantum correlations and entropic uncertainty relation in a three-qubit spin chain under the effect of magnetic field and DM interaction

In this paper, we study the thermal dynamics of quantum correlations and uncertainty relation in a three-qubit spin chain under the effect of Hamiltonian XY model, Dzyaloshinskii–Moriya (DM) interaction and external magnetic field. The results show that quantum correlations behave contrary to uncertainty under the effect of thermal dynamics and external magnetic field. However, they evolve in the same way under effect of DM interaction and spin coupling. DM interaction, magnetic field and spin coupling enhance quantum correlations.

Exploring uncertainty relation and its connection with coherence under the Heisenberg spin model with the Dzyaloshinskii–Moriya interaction

Uncertainty principle is at the heart of quantum physics, taking a fundamental and crucial role in the area of quantum information science, and it provides a remarkable lower bound to quantify our prediction for the measured outcome of two incompatible observables. Herein, the relationship between the lower bound of the measured uncertainty and quantum coherence is investigated under a one-dimensional Heisenberg XXZ spin model with Dzyaloshinskii–Moriya (DM) interactions, and the effect of DM interaction on the entropic uncertainty is also examined in details. We reveal the systematic temperature can give rise to the increase in the measurement uncertainty of interest at thermal equilibrium. By contrast, the stronger coupling strength $$ \left| J \right| $$ or the stronger DM interaction would induce the decrease in the amount with respect to the uncertainty. Moreover, we analyze the dynamical behaviors of quantum coherence and find that the bound of the uncertainty is oppositely correlated with the quantum coherence dramatically. Further, the effects of DM interaction along x-direction (characterized by the parameter Dx) and z-direction (characterized by Dz) on the uncertainty of interest are discussed, respectively. For the antiferromagnetic frame J > 0, it is interesting to obtain that x-direction DM interaction Dx exhibits a more powerful influence on reducing the uncertainty and enhancing the systematic coherence, when comparing with that of Dz. With these in mind, we wish our investigations would better understand the dynamical features of the measured uncertainty in the spin-based solid systems.

Electric field controlled spin waveguide phase shifter in YIG

We propose a new type of a spin waveguide in yttrium iron garnet solely controlled by external electric fields. Spin waves are generated by microwave electric fields while the shift of the phase between spin waves is achieved by means of static electric fields. The phase shifter operation is based on the magneto-electric coupling and effective Dzyaloshinskii Moriya interaction. The special geometry of the waveguide imposes certain asymmetry in the dispersion relationships of the spin waves. Depending on the propagation direction, the phases of the spin waves are shifted differently by the external electric field. The phase difference is entirely controlled by the driving electric fields. The proposed phase shifter can be easily incorporated into electronic circuits and in spin wave logical operations.

Fluctuation-induced Néel and Bloch skyrmions at topological insulator surfaces

Ferromagnets in contact with a topological insulator have become appealing candidates for spintronics due to the presence of Dirac surface states with spin-momentum locking. Because of this bilayer Bi$_2$Se$_3$-EuS structures, for instance, show a finite magnetization at the interface at temperatures well exceeding the Curie temperature of bulk EuS. Here we determine theoretically the effective magnetic interactions at a topological insulator-ferromagnet interface {\it above} the magnetic ordering temperature. We show that by integrating out the Dirac fermion fluctuations an effective Dzyaloshinskii-Moriya interaction and magnetic charging interaction emerge. As a result individual magnetic skyrmions and extended skyrmion lattices can form at interfaces of ferromagnets and topological insulators, the first indications of which have been very recently observed experimentally.

Unraveling Dzyaloshinskii–Moriya Interaction and Chiral Nature of Graphene/Cobalt Interface

A major challenge for future spintronics is to develop suitable spin transport channels with long spin lifetime and propagation length. Graphene can meet these requirements, even at room temperature. On the other side, taking advantage of the fast motion of chiral textures, that is, Néel-type domain walls and magnetic skyrmions, can satisfy the demands for high-density data storage, low power consumption, and high processing speed. We have engineered epitaxial structures where an epitaxial ferromagnetic Co layer is sandwiched between an epitaxial Pt(111) buffer grown in turn onto MgO(111) substrates and a graphene layer. We provide evidence of a graphene-induced enhancement of the perpendicular magnetic anisotropy up to 4 nm thick Co films and of the existence of chiral left-handed Néel-type domain walls stabilized by the effective Dzyaloshinskii-Moriya interaction (DMI) in the stack. The experiments show evidence of a sizable DMI at the gr/Co interface, which is described in terms of a conduction electron mediated Rashba-DMI mechanism and points opposite to the spin orbit coupling-induced DMI at the Co/Pt interface. In addition, the presence of graphene results in (i) a surfactant action for the Co growth, producing an intercalated, flat, highly perfect face-centered cubic film, pseudomorphic with Pt and (ii) an efficient protection from oxidation. The magnetic chiral texture is stable at room temperature and grown on insulating substrate. Our findings open new routes to control chiral spin structures using interfacial engineering in graphene-based systems for future spin-orbitronics devices fully integrated on oxide substrates.

The Dynamics of Quantum Correlations in Multi-qubit Spin Chains Under the Effect of Dzyaloshinskii-Moriya Interaction

Several spin chains with 4 and 6 qubits are considered under the effect of Hamiltonian XY model and Dzyaloshinskii-Moriya (DM) interaction. In this paper, the time evolution of entanglement and quantum discord (quantum correlations) are studied. It is shown that quantum discord is more stable than entanglement. Also the effect of DM interaction depends on initial state and it may improve quantum correlations in spin chains with more than 3 qubits.

Heisenberg and Dzyaloshinskii-Moriya interactions controlled by molecular packing in trinuclear organometallic clusters

Motivated by recent synthetic and theoretical progress we consider magnetism in crystals of multi-nuclear organometallic complexes. We calculate the Heisenberg symmetric exchange and the Dzyaloshinskii-Moriya antisymmetric exchange. We show how, in the absence of spin-orbit coupling, the interplay of electronic correlations and quantum interference leads to a quasi-one dimensional effective spin model in a typical tri-nuclear complex, Mo$_3$S$_7$(dmit)$_3$, despite its underlying three dimensional band structure. We show that both intra- and inter-molecular spin-orbit coupling can cause an effective Dzyaloshinskii-Moriya interaction. Furthermore, we show that, even for an isolated pair of molecules the relative orientation of the molecules controls the nature of the Dzyaloshinskii-Moriya coupling. We show that interference effects also play a crucial role in determining the Dzyaloshinskii-Moriya interaction. Thus, we argue, that multi-nuclear organometallic complexes represent an ideal platform to investigate the effects of Dzyaloshinskii-Moriya interactions on quantum magnets.

Effect of Dzyaloshinskii-Moriya Interaction on Thermal Quantum Correlation in a Two-Qubit Heisenberg XXZ Model with an Inhomogeneous External Magnetic Field

By using the two-qubit Heisenberg XXZ model with Dzyaloshinskii-Moriya (DM) interaction and an inhomogeneous external magnetic field, we investigate the similarities and differences of negativity (N), quantum discord (QD), and measurement-induced disturbance (MID) and the behaviors of quantum phase transition (QPT) at finite temperature. The results indicate that DM interaction D can enhance the N, QD, and MID, while the uniform magnetic field B suppresses them, and the role played by the inhomogeneity b of magnetic field in N is obviously different from those in QD and MID for the smaller D region. Moreover, compared with N, we notice the QD and MID are more general measures of the thermal quantum correlation (TQC). And that the MID cannot completely replace the QD has been discovered. It is also observed that the DM interaction is a more optimal parameter than the inhomogeneous external magnetic field in the process of improving the TQC measured by QD and MID at the higher temperature. In addition, we note that the DM interaction and an inhomogeneous external magnetic field present remarkable different effects on the behavior of the QPT point at finite temperature.

Effect of Dzyaloshinskii-Moriya interaction on the magnetic vortex oscillator driven by spin-polarized current

By micromagnetic simulation, we investigated the dynamic of magnetic vortex driven by spin-polarized current in Permalloy nanodisks in the presence of interfacial/superficial Dzyaloshinskii-Moriya interactions (DMI). It is found that spin-polarized current can drive the vortex precession. In the presence of DMI, the oscillation frequency of the vortex is about 3 times higher than that of without DMI for the same nanodisk. Moreover, the linewidth is more narrow than that of without DMI when the radius of nanodisk is 50 nm. In addition, the vortex can support a higher current density than that of without DMI. Introduction of DMI in this system can provide a new way to design magnetic vortex oscillator.