Kato Naoaki, Kawaguchi Masashi, Lau Yong-Chang, Kikuchi Toru, Nakatani Yoshinobu, Hayashi Masamitsu
Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan.
National Institute for Materials Science, Tsukuba 305-0047, Japan.
Phys Rev Lett. 2019 Jun 28;122(25):257205. doi: 10.1103/PhysRevLett.122.257205.
The Dzyaloshinskii-Moriya (DM) interaction is an antisymmetric exchange interaction that is responsible for the emergence of chiral magnetism. The origin of the DM interaction, however, remains to be identified albeit the large number of studies reported on related effects. It has been recently suggested that the DM interaction is equivalent to an equilibrium spin current density originating from spin-orbit coupling, an effect referred to as the spin Doppler effect. The model predicts that the DM interaction can be controlled by spin current injected externally. Here we show that the DM exchange constant (D) in W/CoFeB-based heterostructures can be modulated with external current passed along the film plane. At higher current, D decreases with increasing current, which we infer is partly due to the adiabatic spin transfer torque. At lower current, D increases linearly with current regardless of the polarity of current flow. The rate of increase in D with the current density agrees with that predicted by the model based on the spin Doppler effect. These results imply that the DM interaction at the heavy-metal-ferromagnetic-metal interface partly originates from an equilibrium interface spin (polarized) current which can be modulated externally.
Dzyaloshinskii-Moriya（DM）相互作用是一种反对称交换相互作用，它是手性磁性出现的原因。然而，尽管已有大量关于相关效应的研究报道，但DM相互作用的起源仍有待确定。最近有人提出，DM相互作用等同于源自自旋轨道耦合的平衡自旋电流密度，这一效应被称为自旋多普勒效应。该模型预测，DM相互作用可以通过外部注入的自旋电流来控制。在此我们表明，基于W/CoFeB的异质结构中的DM交换常数（D）可以通过沿薄膜平面通过的外部电流进行调制。在较高电流下，D随电流增加而减小，我们推断这部分是由于绝热自旋转移力矩所致。在较低电流下，无论电流流动的极性如何，D都随电流线性增加。D随电流密度的增加速率与基于自旋多普勒效应的模型所预测的一致。这些结果表明，重金属-铁磁金属界面处的DM相互作用部分源自可通过外部调制的平衡界面自旋（极化）电流。
