Research On Spin Dynamics Behavior Of Strain-Controlled Magnetic Topology Structure

At present,many different types of magnetic topologi cal structures have been observed experimentally,such as Nell-type skyrmions,Bloch-type skyrmions,skyrmioniums,vortex and magnetic bubbles,etc.Among them,magnetic skyrmions have received the most attention,which is a non-trivial topological spin structure with quasiparticle properties.This new type of magnetic topological structure not only has nanoscale dimensions,but also can be driven by low-density currents with high propagation speed.How to efficiently and stably control these magnetic topological structures is of great significance in both theoretical research and practical applications.Common control techniques include the use of external magnetic fields,local he ating,and spin-polarized current-based spin-transfer torque(STT)effects,but these techniques all suffer from high energy consumption and high Joule heating.In multiferroic heterostructures,a strain-mediated magnetoelectric coupling mechanism can control the magnetization through the inverse magnetostrictive effect.This control method generates almost no current,avoids energy loss caused by Joule heating and damage to the device caused by high temperature,and has the advantages of high efficiency an d speed.Based on the related research on strain-regulated magnetic anisotropy,this paper studies the spin dynamics behavior of strain regulated magnetic topology,including precession modulation of skyrmion breathing modes under strain,skyrmions and skyrmioniums injection and movement,etc.The main contents of the paper are as follows:Aiming at the problems of low oscillation frequency and weak output signal of the spin oscillator based on skyrmion rotation mode,combined with the breathing mode of skyrmion and the strain modulation method in multiferroic heterojunctions,a new method with high performance is proposed.Frequency and frequency-tunable nanospin oscillators.Applying strain can significantly broaden the operating frequency of this oscillat or and increase the strength of its output signal.In addition,using the combined action of current and strain pulses as the tuning excitation of the precession frequency and amplitude of the magnetization,the amplitude modulation and frequency modulation functions of binary information are realized respectively,which provides a new carrier modulation method for future spin oscillators used in digital communication systems.It is inseparable from the injection,movement and detection of spin memory devices based on topological structures,and traditional skyrmion injection methods rely on spin-polarized current-induced magnetization flips.In order to solve the problems of high energy consumption and Joule heating during the current injection of skyrmions,a multiferroic heterostructure with strain-generated skyrmions and skyrmioniums was established by introducing electric strain.The phase diagrams of skyrmions and skyrmion iums stably existing under different DMI parameters and ferromagnetic nanodisk siz es were obtained by micromagnetic simulation calculations,and the radi us of the topological structures under the corresponding parameters were calculated according to the phase diagrams,and it was found found that the size of magnetic topological structures increases with the increase of DMI parameters and the size of ferromagnetic nanodisk.On this basis,by applying different biaxial isotropic in-plane strains and strictly controlling the continuous application time of the strain,the strain writing of skyrmions and skyrmioniums is successfully realized in ferromagnetic nanodisks of different sizes.Skyrmioniums are not affected by the skyrmion Hall effect,and the main ways to drive skyrmioniums to move are spin-polarized currents,spin waves,and anisotropic gradients.In order to solve the thermal effect of the current and reduce the complexity of the device,a gradient-changing strain-driven skyrmioniums was proposed and a nanowires model of a multiferroic heterostructure was established.The app lied strain cannot destroy the magnetization structure of the skyrmion iums.The phase diagram of the stable existence of skyrmioniums under different uniform strains and DMI parameters is obtained by micro-magnetic simulation calculation.On this basis,th e appropriate strain is selected.The gradient successfully drives the skyrmioniums,and the skyrmioniums are found to move in the direction of increasing strain.Comparing the movement of skyrmion iums and skyrmions under the same conditions,it is found t hat skyrmioniums have shorter initiation time and faster speed,while skyrmions have obvious Hall effect and lower speed.In addition,the effects of different strain gradients,Gilbert damping constants(?)and DMI parameters on the movement of skyrmioniums were explored,and it was found that increasing the strain gradient,decreasing ?and increasing DMI could increase the moving speed of skyrmioniums.However,too large strain gradient and too small ? and too much DMI will lead to the deformation of the magnetization structure of the s kyrmioniums.From the perspective of micromagnetic simulation,this paper introduces a multiferroic heterostructure with magnetoelectric coupling effect mediated by strain,and explores the change of the magnetic topological structures in the multiferroic heterostructure under strain.After realizing the regulation of strain on magnetic topological structures,the relationship between the precession and reversal of magnetic moment under strain and the injection of magnetic topological structures,as well as the movement law of strain gradient on magnetic topological structures are further explored.These research results provide a new method for realizing high-efficiency and low-energy spintronic devices based on magnetic topological structures,and provide a certain reference for the follow-up work in this field.