【作者】 程琛；

【导师】 韩秀峰； 夏正才；

【作者基本信息】 华中科技大学 ， 凝聚态物理， 2023， 博士

【摘要】 自旋准粒子可以构造效率更高、寿命更长与集成密度更大的自旋电子学器件,展现了广泛的应用前景。对自旋准粒子输运过程的调控无论在基础物理还是实际应用方面都是推动自旋电子学器件发展的关键。本论文的研究内容主要聚焦于自旋系统中的两种准粒子,即斯格明子与磁子。本文通过理论计算与微磁学模拟,研究了斯格明子与磁子的输运过程调控。本文研究内容如下:(1)研究了存在局域交换偏置场的赛道中的斯格明子在电流驱动下的输运行为,发现了局域交换偏置场导致的斯格明子非对称势垒,并提出了基于局域交换偏置场的斯格明子赛道器件。根据斯格明子在交换偏置场边界所受的非对称势垒,本文设计了斯格明子二极管。研究发现:在二极管中当斯格明子数量增多时,其突破势垒所需的驱动电流呈现递减趋势。在此基础上,本文提出了一种斯格明子神经元结构,通过调节驱动电流的大小,可以改变神经元的激发阈值。(2)研究了椭圆斯格明子在电流驱动下的输运行为,发现了其各向异性驱动现象,并提出了基于椭圆斯格明子的赛道器件。通过引入单轴面内磁各向异性,改变驱动电流与面内磁易轴之间的相对角度可以控制椭圆斯格明子的斯格明子霍尔角。通过优化面内磁各向异性、Dzyaloshinskii-Moriya相互作用与阻尼常数大小,可以改变电流驱动下斯格明子偏离赛道的角度,并且特定条件下可以实现斯格明子零偏离角传输。在此基础上,本文提出了一种实现斯格明子沿赛道运动且无横向偏移的方法。(3)研究了反铁磁耦合磁子晶体中极化磁子的色散关系与输运行为,发现了磁子平带效应。通过引入斯托克斯参数,能够清晰地区分具有相反极化模式的磁子的色散关系,同时磁子平带效应也在其中被观察到。操控反铁磁耦合磁子晶体中自旋相反的磁性子晶格的厚度,可以优化磁子晶体的色散带结构。综合以上特性,本文提出了基于反铁磁耦合磁子晶体的磁子滤波器件。(4)研究了磁子在非均匀温度场中的输运行为,发现了非均匀温度场导致的磁子折射现象。磁子在非均匀温度场传输时,会因饱和磁化强度的非均匀性产生折射效应,磁子路径的折射起源于非均匀磁化强度导致波矢变化所引起的群速度方向改变。基于此理论,本文设计了一种基于温度梯度的磁子透镜,可实现对平行磁子束的聚焦和对发散磁子束的汇聚。更多还原

【Abstract】 Spin quasiparticles provide a route for constructing spintronic devices with superior efficiency,prolonged lifetime,and enhanced integration density,exhibiting broad application prospects.The manipulation of the transport processes of spin quasiparticles is crucial for advancing the development of spintronic devices,both in fundamental physics and applications.This thesis focuses on two types of quasiparticles in spin systems,skyrmion and magnon.By theoretical calculations and micromagnetic simulations,this thesis investigated the transport manipulation of skyrmion and magnon.The main research contents of this thesis are summarized as follows:(1)The transport behavior of skyrmions in racetrack device with local exchange bias field driven by current has been investigated.The asymmetric potential barrier of skyrmions caused by the local exchange bias field has been observed,and skyrmion racetrack device based on the local exchange bias field has been proposed.The skyrmion diode is designed in this study based on the asymmetric potential barrier of skyrmions at the exchange bias field boundary.The study found that an increase in the number of skyrmions results in a decrease in the driving current to overcome the barrier in the diode.Based on the above findings,the skyrmion neuron structure has been proposed in this study,and the fire threshold of neuron can be manipulated by adjusting the driving current.(2)The current-driven transport behavior of elliptical skyrmion has been investigated.The anisotropic driving has been discovered,and the racetrack device based on elliptical skyrmion has been proposed.By introducing uniaxial in-plane magnetic anisotropy,the skyrmion Hall angle of the elliptical skyrmion can be controlled by changing the relative angle between the driving current and the in-plane magnetic easy axis.By optimizing the in-plane magnetic anisotropy,Dzyaloshinskii-Moriya interaction,and damping constant,the angle of deviation of the current-driven skyrmion from the track can be controlled,and the transport of skyrmion with zero divergent angle can be achieved under certain conditions.Based on the above findings,a method for achieving skyrmion motion along the track without any transverse offset has been proposed in this study.(3)The dispersion and transport behavior of polarized magnons in antiferromagnetically coupled magnonic crystals have been investigated,and the magnon flatband effect has been discovered.By introducing Stokes parameters,the dispersion relation of magnons with opposite polarization modes can be clearly distinguished,and the magnon flatband effect can also be observed.By manipulating the thickness of the spinopposite magnetic sublattice in the antiferromagnetically coupling magnonic crystals,the dispersion band structures of the magnonic crystals can be optimized.Based on the above findings,magnon filtering device based on antiferromagnetically coupled magnonic crystals has been proposed in this study.(4)The transport behavior of magnons in the non-uniform temperature field has been investigated,and the refraction of magnons caused by the non-uniform temperature field has been discovered.When the magnons transport in the non-uniform temperature field,the refraction effect will be produced due to the non-uniformity of the saturation magnetization.The refraction of the magnon path arises from the change of the group velocity direction caused by the change of the wave vector caused by the non-uniform magnetization.Based on the above theory,the magnon lens based on temperature gradient has been proposed in this study,which enables the focusing of parallel magnon beams and the convergence of divergent magnon beams.更多还原