垂直点接触自旋霍尔纳米振荡器中自旋波动力学的微磁学模拟  

Micromagnetic simulations of spin-wave dynamics in a vertical nanocontact-based Spin Hall nano-oscillator

作　　者：朱耿宽 高振宇 陈丽娜 周恺元 梁力克 陶醉 刘荣华 Gengkuan Zhu;Zhenyu Gao;Li'na Chen;Kaiyuan Zhou;Like Liang;Zui Tao;Ronghua Liu(Jiangsu Provincial Key Laboratory for Nanotechnology and School of Physics,Nanjing University,Nanjing,210093,China;School of Science,Nanjing University of Posts and Telecommunications,Nanjing,210023,China)

机构地区：[1]江苏省纳米技术重点实验室,南京大学物理学院,南京210093 [2]南京邮电大学理学院,南京210023

出　　处：《南京大学学报（自然科学版）》2023年第2期213-221,共9页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金(11774150,12074178);江苏省青年基金(BK20200309);江苏省纳米技术重点实验室开发基金;南京邮电大学科技基金(NY220164)。

摘　　要：基于微磁学模拟的方法,对垂直点接触自旋霍尔纳米振荡器(VNC-SHNO)中自旋波的激发和其非线性动力行为随电流、磁场及角度的依赖关系进行了详细的数值模拟研究.首先研究了纳米振荡器的频谱特性随激发电流的变化的关系,发现在低电流下,其频谱在远低于铁磁共振频率f_(FMR)处出现一个自旋相干性很好的振荡峰f_(1)以及几个高阶谐波峰,且其频率随电流增加表现出明显的红移;而在高电流下,其频谱除了出现低频f_(1)峰以外,在接近f_(FMR)处还出现了一个高频峰f_(2),但其频率几乎不随激发电流变化.其次,通过振荡模式的功率谱的空间分布图,发现f_(1)是局域在点接触边界的一类非线性“子弹”型自旋孤波,而f_(2)是分布在局域模f_(1)外围的一类准线性传播型自旋波.最后,还细致研究了外加磁场强度及外加磁场面外角度对自旋霍尔纳米振荡器中这两类自旋波的激发和调控规律,为下一步实验研究该器件的非线性动力特性及其在非线性逻辑计算中的应用提供了理论基础.Current-driven coherent spin-waves in a vertical nanocontact-based Spin Hall nano-oscillator(VNC-SHNO)and the dependences of their nonlinear dynamics on the driving current,external magnetic field,and out-of-plane angles are studied systematically with micromagnetism simulations.The spectral characteristics as a function of the driving current find a coherent magnetization oscillating peak f_(1) with a frequency far below the ferromagnetic resonance frequency f_(FMR),and its several high-order harmonic peaks 2f_(1),3f_(1) appear at low currents,and f_(1) shows a significant redshift with increasing current.While,at high currents,in addition to the low-frequency f_(1) peak,a high-frequency peak f_(2) appears near f_(FMR),but its frequency exhibits near independence on the excitation current.Combining these spectral characteristics with the spatial power maps of these two oscillation modes f_(1) and f_(2),we demonstrate that f_(1) is a nonlinearly self-localized"bullet"spin-wave soliton located at the right edge of the top nanocontact,and f_(2) is a quasilinear propagating spin-wave mode distributed around the right periphery of the primary"bullet"mode f_(1).Finally,we summarize the evolution of these two types of spin-waves with the magnitude and out-of-plane angle of the applied magnetic field and,providing a theoretical clue and helpful information for the next experimental exploration of the nonlinear dynamic characteristics of these SHNO devices and their applications in nonlinear logic or neuromorphic computing.

关 键 词：微磁学模拟 自旋霍尔效应 自旋霍尔纳米振荡器 自旋波 

分 类 号：TN01[电子电信—物理电子学]