Individual disk-shaped CoFeB nanodots were driven into a superparamagnetic state by spin transfer torque, and their time-dependent magnetoresistance fluctuations were measured as a function of current. A thin layer of oxidation at the edges has a dramatic effect on the magnetization dynamics. A combination of experimental results and atomistic spin simulations show that pinning to oxide grains can reduce the likelihood that fluctuations lead to reversal, and can even change the easy axis direction. Exchange bias loop shifts and training effects are observed even at room temperature after brief exposure to small fields. The results have implications for studies of core-shell nanoparticles and small magnetic tunnel junctions and spin torque oscillators.

中文翻译：

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超顺磁性Co-Fe-B纳米点的磁阻动力学

各个圆盘状CoFeB纳米点通过自旋传递转矩被驱动为超顺磁性状态，并测量它们随时间变化的磁阻波动作为电流的函数。边缘处的氧化薄层对磁化动力学具有显着影响。实验结果和原子自旋模拟的结合表明，钉扎至氧化物颗粒可以减少波动导致反转的可能性，甚至可以改变易轴方向。即使在室温下短暂暴露于小磁场下，也能观察到交换偏压环的移动和训练效果。该结果对核-壳纳米粒子，小型磁性隧道结和自旋扭矩振荡器的研究具有启示意义。