Dimensional crossover in spin Hall oscillators
Dimensional crossover in spin Hall oscillators
复制标题
DOI：
10.1103/physrevb.102.054422
复制
发表时间：
2020-05
影响因子：
3.7
通讯作者：
Andrew Smith;K. Sobotkiewich;Amanatullah Khan;E. Montoya;Liu Yang;Zheng Duan;T. Schneider;K. Lenz;J. Lindner;Kyongmo An;Xiaoqin Li;I. Krivorotov
中科院分区：
文献类型：
--
作者：
Andrew Smith;K. Sobotkiewich;Amanatullah Khan;E. Montoya;Liu Yang;Zheng Duan;T. Schneider;K. Lenz;J. Lindner;Kyongmo An;Xiaoqin Li;I. Krivorotov
由直接自旋电流驱动的磁化的自振荡先前已经在多个准零维（0 D）铁磁系统（诸如纳米磁体和纳米接触）中观察到。最近，研究表明，纯自旋霍尔电流可以激发准一维（1D）铁磁纳米线的相干自振荡动力学，但不是在准二维（2D）铁磁薄膜。本文研究了Pt/Ni_{80} Fe_{20}$双层自旋霍尔振荡器中电流驱动磁化动力学的一维到二维交叉。我们发现，增加线宽的结果在增加的数量的激发的自振荡模式伴随着每个模式的振幅和相干性的降低。我们还观察到一个交叉从一个硬到一个软发病的自动振荡与增加线的宽度。自振荡的振幅随着温度的升高而迅速减小，这表明相位相干自振荡模式与非相干热磁振子的相互作用在抑制自振荡动力学中起着重要的作用。我们的测量设置的上限上的尺寸的一个单独的自旋霍尔振荡器和阐明的机制，导致抑制相干自振荡与振荡器的大小增加。
Auto-oscillations of magnetization driven by direct spin current have been previously observed in multiple quasi-zero-dimensional (0D) ferromagnetic systems such as nanomagnets and nanocontacts. Recently, it was shown that pure spin Hall current can excite coherent auto-oscillatory dynamics in quasi-one-dimensional (1D) ferromagnetic nanowires but not in quasi-two-dimensional (2D) ferromagnetic films. Here we study the 1D to 2D dimensional crossover of current-driven magnetization dynamics in wire-based Pt/$\mathrm{Ni}_{80}\mathrm{Fe}_{20}$ bilayer spin Hall oscillators via varying the wire width. We find that increasing the wire width results in an increase of the number of excited auto-oscillatory modes accompanied by a decrease of the amplitude and coherence of each mode. We also observe a crossover from a hard to a soft onset of the auto-oscillations with increasing the wire width. The amplitude of auto-oscillations rapidly decreases with increasing temperature suggesting that interactions of the phase-coherent auto-oscillatory modes with incoherent thermal magnons plays an important role in suppression of the auto-oscillatory dynamics. Our measurements set the upper limit on the dimensions of an individual spin Hall oscillator and elucidate the mechanisms leading to suppression of coherent auto-oscillations with increasing oscillator size.