Birck Nanotechnology Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, United States of America.
Department of Physics and Information Technology, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka 820-8502, Japan.
J Phys Condens Matter. 2023 Mar 24;35(21). doi: 10.1088/1361-648X/acc377.
Excitation of magnetization dynamics in magnetic materials, especially in ultrathin ferromagnetic films, is of utmost importance for developing various ultrafast spintronics devices. Recently, the excitation of magnetization dynamics, i.e. ferromagnetic resonance (FMR) via electric field-induced modulation of interfacial magnetic anisotropies, has received particular attention due to several advantages, including lower power consumption. However, several additional torques generated by unavoidable microwave current induced because of the capacitive nature of the junctions may also contribute to the excitation of FMR apart from electric field-induced torques. Here, we study the FMR signals excited by applying microwave signal across the metal-oxide junction in CoFeB/MgO heterostructures with Pt and Ta buffer layers. Analysis of the resonance line shape and angular dependent behavior of resonance amplitude revealed that apart from voltage-controlled in-plane magnetic anisotropy (VC-IMA) torque a significant contribution can also arises from spin-torques and Oersted field torques originating from the flow of microwave current through metal-oxide junction. Surprisingly, the overall contribution from spin-torques and Oersted field torques are comparable to the VC-IMA torque contribution, even for a device with negligible defects. This study will be beneficial for designing future electric field-controlled spintronics devices.
磁性材料中磁化动力学的激发，特别是在超薄铁磁薄膜中，对于开发各种超快速自旋电子学器件至关重要。最近，通过界面磁各向异性的电场诱导调制来激发磁化动力学，即铁磁共振（FMR），由于几个优点，包括更低的功耗，受到了特别关注。然而，由于结的电容性质不可避免地产生的微波电流会产生额外的几个转矩，除了电场诱导的转矩之外，这些转矩也可能有助于 FMR 的激发。在这里，我们研究了在具有 Pt 和 Ta 缓冲层的 CoFeB/MgO 异质结构中通过在金属-氧化物结上施加微波信号来激发的 FMR 信号。共振线形状的分析和共振幅度的角度相关行为表明，除了电压控制的面内磁各向异性（VC-IMA）转矩之外，还可以从通过金属-氧化物结流动的微波电流产生的自旋转矩和奥斯特场转矩中获得显著的贡献。令人惊讶的是，即使对于一个具有可忽略不计的缺陷的器件，自旋转矩和奥斯特场转矩的总贡献也可与 VC-IMA 转矩贡献相媲美。这项研究将有助于设计未来的电场控制自旋电子学器件。
