Impurity-dependent gyrotropic motion, deflection and pinning of current-driven ultrasmall skyrmions in PdFe/Ir(111) surface
Impurity-dependent gyrotropic motion, deflection and pinning of current-driven ultrasmall skyrmions in PdFe/Ir(111) surface
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DOI：
10.1088/1361-648x/ab9cf0
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发表时间：
2020-10-07
影响因子：
2.7
通讯作者：
Lounis, Samir
中科院分区：
文献类型：
--
作者：
Fernandes, Imara Lima;Chico, Jonathan;Lounis, Samir
基于多尺度模型模拟，我们探索了Fe/Ir（111）表面上沉积的Pd层中嵌入的排斥和钉扎3d和4d单原子缺陷的自旋转移矩驱动的磁skyrmions的动力学特征.后者是已知的主机亚10纳米skyrmions这是极大的兴趣在信息技术。Landau-Lifshitz-吉尔伯特方程的参数化与磁交换相互作用提取从头算全电子全势Korringa-Kohn-Rostoker绿色函数方法，其中添加自洽自旋轨道耦合。根据缺陷的性质和所施加磁场的大小，skyrmion通过收缩或增加尺寸而变形，从而经历椭圆扭曲。在施加10 T的磁场后，超小的skyrmions被驱动沿着直线朝向各种缺陷，这允许对杂质的影响进行简单的分析。独立的skyrmion缺陷复杂的相互作用的性质，被排斥或钉扎，一个陀螺运动观察。排斥力导致的skyrmion轨迹类似于吸引力引起的轨迹。我们发现，圆周运动是顺时针周围钉扎杂质，但逆时针周围的排斥，这可以用来识别的相互作用的缺陷，通过观察skyrmions轨迹的性质。此外，正如预期的那样，skyrmion总是逃脱排斥缺陷，而钉扎缺陷则需要最小的脱钉扎电流来观察杂质避免。这揭示了Skyrmions运动机制的丰富性。我们讨论的Thiele方程，它提供了一个合理的定性描述所观察到的现象方面的模拟结果。最后，我们展示了一个例子，一个双轨道的钉扎杂质，在工程上的相互距离允许控制的skyrmion运动与提高速度。
Resting on multi-scale modelling simulations, we explore dynamical aspects characterizing magnetic skyrmions driven by spin-transfer-torque towards repulsive and pinning 3dand 4dsingle atomic defects embedded in a Pd layer deposited on the Fe/Ir(111) surface. The latter is known to host sub-10 nm skyrmions which are of great interest in information technology. The Landau-Lifshitz-Gilbert equation is parametrized with magnetic exchange interactions extracted from the ab-initio all-electron full potential Korringa-Kohn-Rostoker Green function method, where spin-orbit coupling is added self-consistently. Depending on the nature of the defect and the magnitude of the applied magnetic field, the skyrmion deforms by either shrinking or increasing in size, experiencing thereby elliptical distortions. After applying a magnetic field of 10 T, ultrasmall skyrmions are driven along a straight line towards the various defects which permits a simple analysis of the impact of the impurities. Independently from the nature of the skyrmion-defect complex interaction, being repulsive or pinning, a gyrotropic motion is observed. A repulsive force leads to a skyrmion trajectory similar to the one induced by an attractive one. We unveil that the circular motion is clockwise around pinning impurities but counter clockwise around the repulsive ones, which can be used to identify the interaction nature of the defects by observing the skyrmions trajectories. Moreover, and as expected, the skyrmion always escapes the repulsive defects in contrast to the pinning defects, which require a minimal depinning current to observe impurity avoidance. This unveils the richness of the motion regimes of skyrmions. We discuss the results of the simulations in terms of the Thiele equation, which provides a reasonable qualitative description of the observed phenomena. Finally, we show an example of a double track made of pinning impurities, where the engineering of their mutual distance allows to control the skyrmion motion with enhanced velocity.