In-plane Component Of Magnetic Field Research Articles

Manipulation of topological spin textures in centrosymmetric rare-earth magnets

Topologically protected magnetic skyrmions are expected to be used in the next-generation spintronic devices. Realizing their nucleation and manipulation at room temperature is fundamental for future practical applications. Here, using in situ Lorentz transmission electron microscopy and micromagnetic simulation, we demonstrate that magnetic biskyrmions can spontaneously exist at room temperature in Nd1–xTbxCo5 (x = 0.3, 0.5) alloys. The spontaneous biskyrmions are controllably obtained over a wide temperature range across room temperature by switching atomic chemical environment. Furthermore, the density of biskyrmions can be tuned by a small magnetic field. High-density biskyrmions are stimulated to form in the thinner region at room temperature by introducing an in-plane magnetic field component. These results provide valuable insights into the manipulation of topological states, which is of great significance to their practical applications.

Vectorization of magneto-optical images of a in plane component of inhomogeneous magnetic fields

A method based on the magneto-optical Kerr effect is demonstrated, which makes it possible to quantitatively determine spatial dependences of the directions of an in-plane component of inhomogeneous magnetic field visualized by soft nanocrystalline films. The method consists in obtaining magneto-optical images of micromagnetic structures that are formed under the influence of an inhomogeneous field. Images in the longitudinal and transverse sensitivity of the Kerr effect are used to calculate the angular dependence of the directions of the unit vectors of this field under the assumption that the components of the field are proportional to the brightness of magneto-optical images. The field direction maps obtained in this way agree with model calculations for our magnets.

Effect of the in-plane field component on the response of the magneto optical indicator film sensors

In this work we present a study of the effect of the in-plane component of magnetic stray field on the response of Magneto Optical Indicator Film (MOIF) sensors. To take into account this effect, which was neglected in all MOIF measurements done so far, a small bias field with in-plane orientation is applied and the MOIF response thus obtained is compared with the results of numerical modelling. Thus the complete vectorial value of stray field can be determined. Moreover, we show that in a wide range of magnetic fields, up to approximately half the saturation field, the effect of the in-plane field component can be neglected and thus MOIFs are sensitive only to the normal field component, thus making it possible to measure this component directly.

Anisotropy of the in-plane g -factor of electrons in HgTe quantum wells

The results of experimental studies of the Shubnikov-de Haas (SdH) efect in the (013)-HgTe/Hg$_{1-x}$Cd$_x$Te quantum wells (QWs) of electron type of conductivity both with normal and inverted energy spectrum are reported. Comprehensive analysis of the SdH oscillations measured for the different orientations of magnetic field relative to the quantum well plane and crystallographic exes allows us to investigate the anisotropy of the Zeeman effect. For the QWs with inverted spectrum, it has been shown that the ratio of the spin splitting to the orbital one is strongly dependent not only on the orientation of the magnetic field relative to the QW plane but also on the orientation of the in-plane magnetic field component relative to crystallographic axes laying in the QW plane that implies the strong anisotropy of in-plane g-factor. In the QW with normal spectrum, this ratio strongly depends on the angle between the magnetic field and the normal to the QW plane and reveals a very slight anisotropy in the QW plane. To interpret the data, the Landau levels in the tilted magnetic field are calculated within the framework of four-band \emph{kP} model. It is shown that the experimental results can be quantitatively described only with taking into account the interface inversion asymmetry.

Field-Tunable 0-\u03c0-Transitions in SnTe Topological Crystalline Insulator SQUIDs

The manifestation of spin-orbit interactions, long known to dramatically affect the band structure of heavy-element compounds, governs the physics in the surging class of topological matter. A particular example is found in the new family of topological crystalline insulators. In this systems transport occurs at the surfaces and spin-momentum locking yields crystal-symmetry protected spin-polarized transport. We investigated the current-phase relation of SnTe thin films connected to superconducting electrodes to form SQUID devices. Our results demonstrate that an assisting in-plane magnetic field component can induce 0-π-transitions. We attribute these findings to giant g-factors and large spin-orbit coupling of SnTe topological crystalline insulator, which provides a new platform for investigation of the interplay between spin-orbit physics and topological transport.

Composite fermion liquid to Wigner solid transition in the lowest Landau level of zinc oxide

Interactions between the constituents of a condensed matter system can drive it through a plethora of different phases due to many-body effects. A prominent platform for it is a dilute two-dimensional electron system in a magnetic field, which evolves intricately through various gaseous, liquid and solid phases governed by Coulomb interaction. Here we report on the experimental observation of a phase transition between the composite fermion liquid and adjacent magnetic field induced phase with a character of Wigner solid. The experiments are performed in the lowest Landau level of a MgZnO/ZnO two-dimensional electron system with attributes of both a liquid and a solid. An in-plane magnetic field component applied on top of the perpendicular magnetic field extends the Wigner-like phase further into the composite fermion liquid phase region. Our observations indicate the direct competition between a composite fermion liquid and a Wigner solid formed either by electrons or composite fermions.

Imaging spin-resolved cyclotron trajectories in the InSb two-dimensional electron gas

We consider spin-resolved cyclotron trajectories in a magnetic focusing device with quantum point source and drain contacts defined within the InSb two-dimensional electron gas and their mapping by the scanning gate microscopy. Besides the perpendicular component of the external magnetic field which bends the electron trajectories we consider an in-plane component which introduces the spin-dependence of the cyclotron radius. We demonstrate that the focusing conductance peaks become spin-split by the in-plane magnetic field component of the order of a few tesla and that the spin-resolved trajectories can be traced separately with the conductance mapping.

Two-dimensional Hybrid Simulations of Filamentary Structures and Kinetic Slow Waves Downstream of a Quasi-parallel Shock

Abstract In this paper, with two-dimensional hybrid simulations, we study the generation mechanism of filamentary structures downstream of a quasi-parallel shock. The results show that in the downstream both the amplitude of magnetic field and number density exhibit obvious filamentary structures, and the magnetic field and number density are anticorrelated. Detailed analyses find that these downstream compressive waves propagate almost perpendicular to the magnetic field, and the dominant wave number is around the inverse of the ion kinetic scale. Their parallel and perpendicular components roughly satisfy (where and represent the parallel and in-plane perpendicular components of magnetic field, is the wave number in the perpendicular direction, and ρ i in the ion gyroradius), and their Alfvén ratio also roughly agrees with the analytical relation (where R Ai and β indicate the Alfvén ratio and plasma beta, respectively), while the corresponding cross helicity and compressibility show good agreement with previous theoretical calculations. All of these properties are consistent with those of kinetic slow waves (KSWs). Therefore, we conclude that the filamentary structures downstream of a quasi-parallel shock are produced by the excitation of KSWs.

Quantum Hall Spin Diode.

Double layer two-dimensional electron systems at high perpendicular magnetic field are used to realize magnetic tunnel junctions in which the electrons at the Fermi level in the two layers have either parallel or antiparallel spin magnetizations. In the antiparallel case the tunnel junction, at low temperatures, behaves as a nearly ideal spin diode. At elevated temperatures the diode character degrades as long-wavelength spin waves are thermally excited. These tunnel junctions provide a demonstration that the spin polarization of the electrons in the N=1 Landau level at filling factors ν=5/2 and 7/2 is essentially complete, and, with the aid of an in-plane magnetic field component, that Landau level mixing at these filling factors is weak in the samples studied.

Influences of non-uniformities and anisotropies on the flux avalanche behaviors of type-II superconducting films

In this paper, the anisotropic flux avalanche processes in thin square-shaped type-II superconducting films are numerically investigated by solving the coupled nonlinear Maxwell’s equations and the thermal diffusion equations. Influences of the non-uniformities and intrinsic critical current density anisotropies originate from the manufacturing process are considered in the simulation. In addition, we also studied the effect of the extrinsic anisotropy induced by the in-plane magnetic field. The results demonstrate that the non-uniformities and anisotropies of the critical current density play significant roles in the flux avalanche process of the thin film superconductors. Slight anisotropy (either intrinsic or extrinsic) can dramatically change the propagation direction of avalanches in the superconducting film, which is consistent with the experimental results. Simulations on the thin square-shaped isotropic superconducting films show that the threshold magnetic field for the flux avalanches increases with the angle between the applied field and the superconducting film-plane. In addition, the flux avalanche patterns change with the angular variation of the in-plane component of external magnetic field. When the in-plane magnetic field component is along the diagonal lines of the superconducting square, symmetric flux avalanche penetration patterns occur to the film.

Compact two-dimensional CMOS Hall sensor based on switchable configurations of four three-contact elements

This paper reports a novel CMOS sensor of compelling design simplicity for the measurement of both in-plane magnetic field components Bx and By at the same location. The device is operated through only four contacts and using a single control signal. It consists of four separate n-wells arranged as two orthogonal pairs. Each n-well segment forms a three-contact vertical Hall element (3CVHE) whose two outer contacts are used for the electrical interconnection of the four 3CVHEs into a conducting loop. The central contacts of each 3CVHE serve as drive and sense contacts enabling offset reduction by the spinning-current method. The operating principle of the novel device is derived from the magnetic field dependent resistance matrix of the individual 3CVHEs. The two-axis sensing capability of the sensor is achieved by selectively switching the interconnections among the four 3CVHEs, whereby the device is made sensitive alternatingly to Bx and By. Integrated transmission gates (TG) serve as switches. Appropriate design ensures the electrical symmetry of the sensor, which results in a low equivalent offset field of 0.2 to 0.4mT. For a nominal B field of 3.7mT the RMS error of the measured magnitude and angle of B are extracted to be only 42 μT and 0.7°, respectively.

Large magnetic anisotropy in canted antiferromagneticSr2IrO4single crystals

The magnetocrystalline contribution to magnetic anisotropy was studied in the canted antiferromagnetic state of layered ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ single crystals. We performed torque measurements in magnetic fields up to 9 T under various magnetic field orientations. The strong dependence of torque on the magnetic field revealed that the magnetic easy axis is along the in-plane direction and that the observed field-induced weak ferromagnetic order is attributed only to the in-plane component of the external magnetic field. The dependence of torque on the angle produces a twofold symmetric sawtoothlike shape. A simple model consisting of canted antiferromagnetic and magnetic induction terms showed good agreement with the measured torque. These results show that magnetic anisotropy is closely related to the anisotropy of the exchange between antiferromagnetic moments whose canting is mediated by the Dzyaloshinsky-Moriya interaction. Our study demonstrates that torque magnetometry can be extended to the investigation of the magnetic anisotropy of complex magnetic phases.

Quantum oscillations in Weyl and Dirac semimetal ultrathin films

We show that a thin film of Weyl or Dirac semimetal with a strong in-plane magnetic field becomes a novel two-dimensional Fermi liquid with interesting properties. The Fermi surface in this system is strongly anisotropic, which originates from a combination of chiral bulk channels and the Fermi arcs. The area enclosed by the Fermi surface depends strongly on the in-plane magnetic field component parallel to the Weyl/Dirac node splitting, which leads to unusual behavior in quantum oscillations when the magnetic field is tilted out of the plane. We estimate the oscillation frequencies and the regimes where such effects could be seen in Cd$_3$As$_2$, Na$_3$Bi, and TaAs.

2D in-plane Hall Sensing Based on a New Microdevice Coupling Concept

A 2D Hall microdevice for synchronous measurement of two in-plane magnetic-field components, using an original coupling concept based on two identical parallel-field three-contact (3C) silicon Hall elements positioned at right angle and integrated on the same chip, is presented. The two pairs of outer contacts of 3C Hall transducers are connected via two load resistors, converting simultaneously and independently the current changes in Bx and By magnetic fields into Hall voltages. Since the supply currents in both structures are equal, the magnetosensitivities are the same, too. At a fabrication of the devices on a common silicon chip, the output temperature drifts are perfectly matched. The high measurement accuracy, performance and compensated channel offsets of this 2D magnetometer are achieved by the minimal interface components between both sensors. The suggested sensing microsystem is appropriate for many contactless measurement instruments.

Dynamic analysis of a ferromagnetic structure in strong magnetic field with electromagneto-mechanical coupling

In this paper, a numerical method is proposed for simulating dynamic response of a ferromagnetic structure im- mersed in a strong magnetic field aiming at applications to the in vessel Tokamak structure of RAFM steel. The magnetic damping coupling effect and the magnetic stiffness coupling effect are considered in the numerical simulation. For simple, the static magnetic field is supposed very strong and the material is considered saturated in this work, i.e., the material is of air permeability but with a strong residual magnetization. To demonstrate the validity of the numerical method, the dynamic response of a ferromagnetic plate immersed in a transient transverse magnetic field with in-plane magnetic field component is simulated with the developed numerical code and compared with the simulated results with ANSYS. The good consistency of numerical results and simulation results demonstrated the validity of the proposed method and the corresponding numerical code.

Electric Field-Induced Magnetization Switching in CoFeB-MgO—Static Magnetic Field Angle Dependence

We investigate switching probabilities of electric field-induced magnetization switching in CoFeB/MgO based magnetic tunnel junction with perpendicular magnetic easy axis under static magnetic field with various directions. The switching takes place through magnetization precession with the period determined by the magnitude of the in-plane component of magnetic field. The experimental results are well reproduced by macro-spin simulation. The simulation reveals that decoherence induced by thermal fluctuations and/or other effects limit the switching probabilities in the present system.

Ultra-low Offset Vertical Hall Sensor in CMOS Technology

This paper reports on a novel vertical Hall sensor with ultra-low offset (ULOVHS) for the measurement of an in-plane magnetic field component. The sensor consists of four parallel coupled fully symmetric vertical Hall sensors (FSVHS). Each FSVHS is formed by the connection of four identical three-contact vertical Hall elements (3CVHE). As a result, with a bias current of 0.5mA and after current switching, a mean residual offset of 0.27μV with a standard deviation of 0.29μV has been achieved among 40 samples on an 8-inch wafer, which is an improvement of a factor of 16 compared to the FSVHS (4.2±14μV). Furthermore, the measured current related sensitivity of the novel device is SI = 12.65V/AT, allowing the detection of magnetic fields down to Bmin = 40μT without any additional electrical compensation circuitry. This represents the best results to date achieved by a stand- alone VHS in standard CMOS technology.

Impact of eddy currents on the dispersion relation of surface spin waves in thin conducting magnetic films

We propose a rigorous solution to a long-standing problem of the impact of eddy currents on the dispersion relation of surface spin waves propagating in thin conducting magnetic films. Our results confirm the prediction of the Almeida–Mill's exchange-free theory that the inclusion of the eddy-current contribution results in a deviation of the dispersion curve for the fundamental mode from the Damon–Eshbach law and a substantial linewidth broadening in a large wave vector range. We show that the decrease in the spin-wave frequency is due to an increase in the in-plane component of the dynamic magnetic field within the conducting film. The decrease in the frequency is accompanied by a drastic change in the asymmetry of the modal profiles for the waves. This effect is not observable in magneto-insulating films and therefore it is unambiguously attributed to eddy currents that appear in conducting films only. We also show that the wave vector range in which eddy currents affect the dispersion curve is strongly correlated with the value of the film conductivity. This result holds for conducting films with the thickness 10–100 nm, which are considered promising for future magnonic and spintronic applications.

Alternative method for the quantitative determination of Rashba- and Dresselhaus spin–orbit interaction using the magnetization

The quantum oscillatory magnetization M of a two-dimensional electron system in a magnetic field B is found to provide quantitative information on both the Rashba- and Dresselhaus spin–orbit interaction (SOI). This is shown by first numerically solving the model Hamiltonian including the linear Rashba- and Dresselhaus SOI and the Zeeman term in particular in a doubly tilted magnetic field and second evaluating the intrinsically anisotropic magnetization for different directions of the in-plane magnetic field component. The amplitude of specific magnetic quantum oscillations in M(B) is found to be a direct measure of the SOI strength at fields B where SOI-induced Landau level anticrossings occur. The anisotropic M allows one to quantify the magnitude of both contributions as well as their relative sign. The influence of cubic Dresselhaus SOI on the results is discussed. We use realistic sample parameters and show that recently reported experimental techniques provide a sensitivity which allows for the detection of the predicted phenomena.

In-plane magnetic field dependence of electric field-induced magnetization switching

Electric field-induced magnetization switching through magnetization precession is investigated as a function of in-plane component of external magnetic field for a CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis. The switching probability is an oscillatory function of the duration of voltage pulses and its magnitude and period depend on the magnitude of in-plane magnetic field. Experimental results are compared with simulated ones by using Landau-Lifshitz-Gilbert-Langevin equation, and possible factors determining the probability are discussed.