Cui Baoshan, Li Dong, Yun Jijun, Zuo Yalu, Guo Xiaobin, Wu Kai, Zhang Xu, Wang Yupei, Xi Li, Xue Desheng
Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education & School of Physical Science and Technology, Lanzhou University, P. R. China.
Phys Chem Chem Phys. 2018 Apr 18;20(15):9904-9909. doi: 10.1039/c7cp08352a.
Heavy metal/ferromagnetic layers with perpendicular magnetic anisotropy (PMA) have potential applications for high-density information storage in racetrack memories and nonvolatile magnetic random access memories. In these devices, deterministic magnetization switching has been achieved via electric current induced spin orbital torques (SOTs) with the assistance of a current directional external in-plane bias field, which causes technological obstacles for the real application of SOT based spintronic devices. Here, we report that reversible field-free magnetization switching could be achieved via current-driven domain wall motion (DWM) in Pt/Co/Cr micro-sized racetracks with PMA owing to the preformation of the homochiral Néel-type domain wall, in which an in-plane inherent Dzyaloshinskii-Moriya interaction field was generated acting as the external in-plane bias field to break the symmetry. A full magnetization switching can be realized in this device based on the enhanced SOTs from a dedicated design of Pt/Co/Cr structures with Pt and Cr showing opposite signs of spin Hall angles. Therefore, the generated spin currents are expected to work in concert to improve the SOTs. We also demonstrated that the simultaneously accompanying Joule heating effect also plays a key role in the field-free magnetization switching process, including the propagation field as well as the domain wall motion velocity.
具有垂直磁各向异性（PMA）的重金属/铁磁层在赛道存储器和非易失性磁性随机存取存储器的高密度信息存储方面具有潜在应用。在这些器件中，通过电流诱导的自旋轨道矩（SOT）并借助电流方向的外部面内偏置场实现了确定性磁化翻转，这给基于SOT的自旋电子器件的实际应用带来了技术障碍。在此，我们报道，由于同手性奈尔型畴壁的预先形成，在具有PMA的Pt/Co/Cr微型赛道中，通过电流驱动的畴壁运动（DWM）可以实现无场可逆磁化翻转，其中面内固有Dzyaloshinskii-Moriya相互作用场作为外部面内偏置场产生，以打破对称性。基于具有自旋霍尔角符号相反的Pt和Cr的Pt/Co/Cr结构的专门设计所增强的SOT，在该器件中可以实现完全磁化翻转。因此，所产生的自旋电流有望协同作用以改善SOT。我们还证明，同时伴随的焦耳热效应在无场磁化翻转过程中也起着关键作用，包括传播场以及畴壁运动速度。
