Skyrmion motion induced by spin-waves on magnetic nanotubes

We investigate the skyrmion motion driven by spin waves on magnetic nanotubes through micromagnetic simulations.Our key results include demonstrating the stability and enhanced mobility of skyrmions on the edgeless nanotube geometry,which prevents destruction at boundaries—a common issue in planar geometries.We explore the influence of the damping coefficient,amplitude,and frequency of microwaves on skyrmion dynamics,revealing a non-uniform velocity profile characterized by acceleration and deceleration phases.Our results show that the skyrmion Hall effect is significantly modulated on nanotubes compared to planar models,with specific dependencies on the spin-wave parameters.These findings provide insights into skyrmion manipulation for spintronic applications,highlighting the potential for high-speed and efficient information transport in magnonic devices.

Spin pumping by higher-order dipole-exchange spin-wave modes

Spin pumping(SP)and inverse spin Hall effect(ISHE)driven by parametrically-excited dipole-exchange spin waves in a yttrium iron garnet film have been systematically investigated.The measured voltage spectrum exhibits a feature of the field-induced transition from parallel pumping to perpendicular pumping because of the inhomogeneous excitation geometry.Thanks to the high precision of the SP-ISHE detection,two sets of fine structures in the voltage spectrum are observed,which can correspond well to two kinds of critical points in the multimode spin-wave spectrum for magnetic films.One is the q=0 point of each higher-order dispersion branch,and the other is the local minimum due to the interplay between the dipolar and exchange interactions.These fine structures on the voltage spectrum confirm the spin pumping by higher-order dipole-exchange spin-wave modes,and are helpful for probing the multimode spin-wave spectrum.

Shape-manipulated spin-wave eigenmodes of magnetic nanoelements

The magnetization dynamics of nanoelements with tapered ends have been studied by micromagnetic simulations.Several spin-wave modes and their evolutions with the sharpness of the element ends are characterized. The edge mode localized in the two ends of the element can be effectively tuned by the element shape. Its frequency increases rapidly with the tapered parameter h and its localized area gradually expands toward the element center, and it finally merges into the fundamental mode at a critical tapered parameter h0. For nanoelements with h 〉 h0, the edge mode is completely suppressed. The standing spin-wave modes mainly in the internal area of the element are less affected by the element shape.The shifts of their frequencies are small and they display different tendencies. The evolution of the spin-wave modes with the element shape is explained by considering the change of the internal field.

Self-Consistent Spin-Wave Analysis of the 1/3 Magnetization Plateau in the Kagome Antiferromagnet

We propose a modified spin-wave theory to study the 1/3 magnetization plateau of the antiferromagnetic Heisen- berg model on the kagome lattice. By the self-consistent inclusion of quantum corrections, the 1/3 plateau is stabilized over a broad range of magnetic fields for all spin quantum numbers S. The values of the critical mag- netic fields and the widths of the magnetization plateaus are fully consistent with the recent numerical results from exact diagonalization and infinite projected entangled paired states.

A Self-consistent Calculation and an Anisotropic Wavelength Cut off Energy of Spin-wave Spectrumin Magnetic Tunnel Junctions

Temperature dependence of tunnel magnetoresistance (TMR) ratio, resistance, and coercivity from 4.2 K to room temperature (RT), applied de bias voltage dependence of the TMR ratio and resistances at 4.2 K and RT, tunnel current I and dynamic conductance dI/dV as functions of the de bias voltage at 4.2 K, and inelastic electron tunneling (IET) spectroscopy, d(2)I/dV(2) versus V, at 4.2 K for a tunnel junction of Ta(5 nm)/Ni79Fe21(25 nm)/Ir22Mn78(12 nm)/Co75Fe25(4 nm)/Al(0.8 nm)-oxide/Co75Fe25(4 nm)/Ni79Fe21(25 nm)/Ta(5 nm) were systematically investigated. High TMR ratio of 59.2% at 4.2 K and 41.3% at RT were observed for this junction after annealing at 275 degreesC for an hour. The temperature dependence of TMR ratio and resistances from 4.2 to 300 K at 1.0 mV bias and the de bias voltage dependence of TMR ratio at 4.2 K from 0 to 80 mV can be evaluated by a comparison of self-consistent calculations with the experimental data based on the magnon-assisted inelastic excitation model and theory. An anisotropic wavelength cutoff energy of spin-wave spectrum in magnetic tunnel junctions (MTJs) was suggested, which is necessary for self-consistent calculations, based on a series of IET spectra observed in the MTJs.

Recent progress on excitation and manipulation of spin-waves in spin Hall nano-oscillators

Spin Hall nano oscillator(SHNO),a new type spintronic nano-device,can electrically excite and control spin waves in both nanoscale magnetic metals and insulators with low damping by the spin current due to spin Hall effect and interfacial Rashba effect.Several spin-wave modes have been excited successfully and investigated substantially in SHNOs based on dozens of different ferromagnetic/nonmagnetic(FM/NM)bilayer systems(e.g.,FM=Py,[Co/Ni],Fe,CoFeB,Y3Fe5O12;NM=Pt,Ta,W).Here,we will review recent progress about spin-wave excitation and experimental parameters dependent dynamics in SHNOs.The nanogap SHNOs with in-plane magnetization exhibit a nonlinear self-localized bullet soliton localized at the center of the gap between the electrodes and a secondary high-frequency mode which coexists with the primary bullet mode at higher currents.While in the nanogap SHNOs with out of plane magnetization,besides both nonlinear bullet soliton and propagating spin-wave mode are achieved and controlled by varying the external magnetic field and current,the magnetic bubble skyrmion mode also can be excited at a low in-plane magnetic field.These spin-wave modes show thermal-induced mode hopping behavior at high temperature due to the coupling between the modes mediated by thermal magnon mediated scattering.Moreover,thanks to the perpendicular magnetic anisotropy induced effective field,the single coherent mode also can be achieved without applying an external magnetic field.The strong nonlinear effect of spin waves makes SHNOs easy to achieve synchronization with external microwave signals or mutual synchronization between multiple oscillators which improve the coherence and power of oscillation modes significantly.Spin waves in SHNOs with an external free magnetic layer have a wide range of applications from as a nanoscale signal source of low power consumption magnonic devices to spin-based neuromorphic computing systems in the field of artificial intelligence.

SPIN-WAVE THEORY OF 1D SPIN-1/2 QUANTUM CHAIN WITH INTERACTIONS TO THIRD NEIGHBOURS

The one dimensional spin 1/2 quantum chain with competing interactions is studied. The ground state energy and the elementary excitations are found by the spin wave theory and the equations of motion with decoupling approximation. As required, the excitation energies are triply degenerated.

INTERFACE SPIN-WAVE OF COUPLED SEMI-INFINITE MAGNETIC SUPERLATTICE

The interface spin-wave (ISW) modes or coupled semi-infinitemagnetic superlattices separated by a nonmagnetic layer have been studied by use of the magnetostatic method, A general expression of the ISW dispersion relation is obtained. Detailed calculations are performed in the special case where the ttwo semi-infinite superlattices is considered to be identical and the external magnetic field is parallel or perpendicular to the surface of the layers. Some results about ISW modes are discussed.

Intrinsic Localized Spin-Wave Modes in an Anisotropic Ferromagnet with Dzyaloshinsky–Moriya Interaction

The existence and properties of intrinsic localized spin-wave modes in a ferromagnetic XXZ spin chain with Dzyaloshinsky–Moriya interaction are investigated analytically in the semiclassical limit. The model Hamiltonian is quantized by introducing the Dyson–Maleev transformation and the coherent state representation is chosen as the basic representation of the system. By making use of the method of multiple scales combined with a quasidiscreteness approximation, the equation of motion for the coherent-state amplitude is reduced to the nonlinear Schr¨odinger equation.It is shown that a bright intrinsic localized spin-wave mode whose eigenfrequency lies below the bottom of the magnon frequency band can exist in the ferromagnetic system. We also show that the system can produce a dark intrinsic localized spin-wave mode, i.e., nonpropagating kink, whose eigenfrequency is below the upper of the magnon frequency band. In addition, we find that the introduction of the Dzyaloshinsky–Moriya interaction changes wave numbers in the Brillouin-zone corresponding to the appearance of intrinsic localized spin-wave modes.

Spin-Wave Analysis of the Spin-1 Two-Dimensional Frustrated Heisenberg Antiferromagnet with the Single-Ion Anisotropy

In this paper, the lowtemperature properties of the spin1 twodimensionM frustrated Heisenberg antifer romagnet with the singleion anisotropy are investigated on a square lattice by using the spinwave theory. The influence of the frustration and anisotropy is found in the thermodynamics of the model, such as the temperature dependence of the staggered magnetization and specific heat. For some selected values of the frustration and anisotropy parameters, the results for the specific heat are compared with those of existing theories and numerical estimates. Within a spinwave analysis, we have found the evidence for an intermediate magnetically disorder phase to separate the Nel and collinear phases.

Magnetocrystalline anisotropy and spin-wave stiffness in tensilestrained La_(0.67)Ba_(0.33)MnO_3 films:An investigation via ferromagnetic resonance

Tensile-strained epitaxial La0.67Ba0.33MnO3(LBMO)film has been prepared by magnetron sputtering technique on(001)oriented spinel MgAl2O4substrate.The transport and magnetic measurements give an insulator-metal transition and paramagnetic-ferromagnetic transition occurring at^150 K and 250 K respectively,which implies the phase separation in such a tensile-strained film.By analyzing the angular and temperature dependences of the ferromagnetic resonance(FMR),we determine the magnetocrystalline anisotropy of the film.It is found that the tensile-strained film is dominated by an easy-axis corresponding to the compressive out-of-plane direction,though the magnitudes of anisotropy constants are relatively small and their temperature dependences are some complex.Furthermore,the FMR spectra show additional spin wave resonance(SWR),and the field positions can be indexed to follow a linear dependence on the square of index n.The scaling gives a spin-wave exchange stiffness D of 20.7 meV 2at low temperature,which is less than half of that in strain-free LBMO films,implying that the double exchange interaction is remarkably suppressed in the tensile-strained LBMO films.

铁磁畴壁中自旋极化电流诱导的左旋极化自旋波

极化指的是波偏振的方式,是波的一个基本性质.利用波的极化可以进行信息的编码,这一编码方式在光学和声学中得到广泛应用.利用自旋波进行信息的传递和处理是磁子学的主要研究课题.然而在铁磁材料中,由于只存在右旋极化的自旋波,利用波的极化进行信息的编码在铁磁自旋波器件中始终没有实现.前期研究发现,通过自旋极化电流可以在铁磁体中产生左旋极化自旋波,从而有望实现利用极化编码的自旋波器件.然而在一个均匀磁化铁磁体中产生左旋极化自旋波所需的电流密度过大,实验上难以实现.磁畴壁可作为自旋波波导,且畴壁中自旋波的截止频率趋近于零.本文从朗道-栗弗席兹方程出发,研究了在自旋极化电流存在的条件下磁畴壁中自旋波的色散关系和传播特性,证明只需要很小的自旋极化电流就可在畴壁中产生稳定的左旋极化自旋波.微磁学模拟证明了理论分析结果.该项研究为研制基于极化编码信息的自旋波器件提供了一个实际可行的方案.

双层蜂窝状海森伯铁磁体中层间交换耦合相互作用对拓扑相的影响

层状磁性拓扑材料是最小二维单元下同时具有磁序和拓扑性的材料体系,研究这一体系可能会观察到新物性和新现象的出现,因此引起了研究者们的广泛关注.本文运用线性自旋波理论,主要研究了层间铁磁耦合的双层蜂窝状海森伯铁磁体中层间交换耦合相互作用对系统拓扑相的影响.通过计算不同层间交换耦合相互作用强度下的磁子色散关系能得出,当系统达到两个强度临界值时,能量较高的两条能带和能量较低的两条能带的带隙在狄拉克点处会依次出现闭合-重新打开现象.计算能带对应的贝里曲率和陈数后,发现贝里曲率符号在相应临界值前后会发生反转,同时陈数也会发生改变,这证明系统发生了拓扑相变.此外,本文研究发现当双层蜂窝状铁磁体发生拓扑相变时,磁子热霍尔系数变化曲线会相应发生突变.本研究成果可以为利用双层蜂窝状铁磁材料制作具有更高信息传输能力的自旋电子器件提供理论支撑,也可以为其他双层铁磁系统的相关研究提供一定的理论参考.

声表面波-自旋波耦合及磁声非互易性器件

声表面波是激发和控制自旋波的一种新兴手段,不仅激励效率高,而且传输长度可以达到毫米量级,通过引入磁声耦合还可以打破时空反演对称性,实现声表面波的非互易传播.本文对不同类型的磁声耦合的物理机制进行了梳理,对比了磁弹性耦合、自旋-涡度耦合(包括非磁性层注入交变自旋流和磁性材料自身的Barnett效应),以及磁-旋转耦合在不同模式的声表面波激发下的等效驱动磁场,讨论了这些等效驱动场的角度依赖性,以及相应功率吸收的频率依赖性.这为在实际应用中区分和利用各种磁声耦合机制提供了理论支持.此外,本文还介绍了利用磁声耦合实现声表面波非互易性传输的两种主流手段,包括利用手性失配效应和引入具有非互易性自旋波色散关系的磁结构,对比并讨论了它们各自的物理机制和优劣势,希望为设计和发展基于磁声耦合的固态声学隔离器、环形器提供参考.

弯曲应变下六角晶格量子反铁磁体的赝朗道能级

利用线性自旋波理论和量子蒙特卡罗方法研究了弯曲应变下六角晶格量子反铁磁体的赝朗道能级.通过线性自旋波理论,发现磁赝朗道能级出现在磁子能谱的高能端,其能级间距与能级指数的平方根成正比.线性自旋波理论和量子蒙特卡罗方法都显示,尺寸相同时随着应变强度的逐渐增加,局域磁化强度逐渐减弱,应变强度相同的条件下反铁磁序在y方向上连续减弱,因为上边界处的海森伯链解耦为孤立的垂直链,导致上边界附近的磁序被破坏.量子蒙特卡罗方法提供了更精确的反铁磁序演化:在特定应变强度下上边界处垂直关联不变,水平关联增加,从而影响磁化强度,使局域磁化在上边界处呈上翘趋势.研究结果有助于理解弯曲应变对自旋激发的影响,并可能在二维量子磁性材料实验中得以实现.

磁性薄膜的次表面自旋波分布及影响因素分析

为了了解铁磁性薄膜中局域自旋波的性质,基于海森堡模型利用量子格林函数方法对铁磁性薄膜的自旋波分布进行了研究,分析了外部物理因素(温度和外磁场)和薄膜表面性质(表面各向异性和表面交换耦合)对表面布里渊区内次表面自旋波存在区域的影响,并比较了表面与次表面自旋波性质的差异.结果表明:温度和外磁场对次表面自旋波存在区域的影响规律相似,而表面各向异性和表面交换耦合对次表面自旋波存在区域的影响规律相似;次表面自旋波的存在区域始终小于表面自旋波的存在区域.

AB双层磁性薄膜的界面自旋波

针对非对称AB双层磁性薄膜中自旋波的分布问题,采用量子格林函数方法研究了不同界面参数对界面自旋波在二维布里渊区中占有面积的影响.结果表明:非对称AB双层磁性薄膜中存在两支界面自旋波,第4原子层界面自旋波存在于中温区间,第5原子层界面自旋波存在于全温区间;随着温度的升高,两支界面自旋波的占有面积先增大后减小;随着外磁场的升高,两支界面自旋波的占有面积减小;随着界面层间交换耦合、界面层内交换耦合和界面各向异性的增加,第4原子层界面自旋波的占有面积增加,第5原子层界面自旋波的占有面积减小.

In-plane spin excitation of skyrmion bags

Skyrmion bags are spin structures with arbitrary topological charges, each of which is composed of a big skyrmion and several small skyrmions. In this work, by using an in-plane alternating current(AC) magnetic field, we investigate the spinwave modes of skyrmion bags, which behave differently from the clockwise(CW) rotation mode and the counterclockwise(CCW) rotation mode of skyrmions because of their complex spin topological structures. The in-plane excitation power spectral density shows that each skyrmion bag possesses four resonance frequencies. By further studying the spin dynamics of a skyrmion bag at each resonance frequency, the four spin-wave modes, i.e., a CCW-CW mode, two CW-breathing modes with different resonance strengths, and an inner CCW mode, appear as a composition mode of outer skyrmion–inner skyrmions. Our results are helpful in understanding the in-plane spin excitation of skyrmion bags, which may contribute to the characterization and detection of skyrmion bags, as well as the applications in logic devices.

毫米波高功率NiZn铁氧体材料研究

本文针对毫米波高功率环行器对微波铁氧体材料的技术要求,开展了高功率NiZn铁氧体材料的研究工作。在理论分析的基础上,固化制备工艺参数,通过配方Zn^(2+)、Co^(2+)掺杂,得到饱和磁化强度和自旋波线宽的变化规律,最终研制出饱和磁化强度到达4008Gs、自旋波线宽达到28.3Oe的毫米波高功率铁氧体材料,满足了器件使用需求。

Mathematical Wave Functions and 3D Finite Element Modelling of the Electron and Positron

The wave/particle duality of particles in Physics is well known. Particles have properties that uniquely characterize them from one another, such as mass, charge and spin. Charged particles have associated Electric and Magnetic fields. Also, every moving particle has a De Broglie wavelength determined by its mass and velocity. This paper shows that all of these properties of a particle can be derived from a single wave function equation for that particle. Wave functions for the Electron and the Positron are presented and principles are provided that can be used to calculate the wave functions of all the fundamental particles in Physics. Fundamental particles such as electrons and positrons are considered to be point particles in the Standard Model of Physics and are not considered to have a structure. This paper demonstrates that they do indeed have structure and that this structure extends into the space around the particle’s center (in fact, they have infinite extent), but with rapidly diminishing energy density with the distance from that center. The particles are formed from Electromagnetic standing waves, which are stable solutions to the Schrödinger and Classical wave equations. This stable structure therefore accounts for both the wave and particle nature of these particles. In fact, all of their properties such as mass, spin and electric charge, can be accounted for from this structure. These particle properties appear to originate from a single point at the center of the wave function structure, in the same sort of way that the Shell theorem of gravity causes the gravity of a body to appear to all originate from a central point. This paper represents the first two fully characterized fundamental particles, with a complete description of their structure and properties, built up from the underlying Electromagnetic waves that comprise these and all fundamental particles.