Research and Development Group, Hitachi, Ltd., 1-280 Higashi-koigakubo, Kokubunji-shi, Tokyo 185-8601, Japan.
Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan.
Sci Rep. 2017 Feb 17;7:42511. doi: 10.1038/srep42511.
Recent progress in magnetic tunnel junctions (MTJs) with a perpendicular easy axis consisting of CoFeB and MgO stacking structures has shown that magnetization dynamics are induced due to voltage-controlled magnetic anisotropy (VCMA), which will potentially lead to future low-power-consumption information technology. For manipulating magnetizations in MTJs by applying voltage, it is necessary to understand the coupled magnetization motion of two magnetic (recording and reference) layers. In this report, we focus on the magnetization motion of two magnetic layers in MTJs consisting of top layers with an in-plane easy axis and bottom layers with a perpendicular easy axis, both having perpendicular magnetic anisotropy. According to rectified voltage (V) measurements, the amplitude of the magnetization motion depends on the initial angles of the magnetizations with respect to the VCMA direction. Our numerical simulations involving the micromagnetic method based on the Landau-Lifshitz-Gilbert equation of motion indicate that the magnetization motion in both layers is induced by a combination of VCMA and transferred angular momentum, even though the magnetic easy axes of the two layers are different. Our study will lead to the development of voltage-controlled MTJs having perpendicular magnetic anisotropy by controlling the initial angle between magnetizations and VCMA directions.
近年来，具有垂直易轴的磁性隧道结 (MTJ) 在 CoFeB 和 MgO 堆叠结构方面取得了进展，研究表明，由于电压控制磁各向异性 (VCMA)，磁动力学会被诱导，这将为未来低功耗信息技术奠定基础。为了通过施加电压来控制 MTJ 中的磁化，有必要了解两个磁性（记录和参考）层的耦合磁化运动。在本报告中，我们专注于由具有平面易轴的顶层和具有垂直易轴的底层组成的 MTJ 中的两个磁性层的磁化运动，这两层都具有垂直各向异性。根据修正电压 (V) 测量，磁化运动的幅度取决于磁化相对于 VCMA 方向的初始角度。我们基于运动方程的 Landau-Lifshitz-Gilbert 方程的基于微磁方法的数值模拟表明，即使两个层的磁易轴不同，两个层中的磁化运动都是由 VCMA 和转移角动量共同诱导的。通过控制磁化和 VCMA 方向之间的初始角度，我们的研究将导致具有垂直各向异性的电压控制 MTJ 的发展。
