Quessab Yassine, Xu Jun-Wen, Morshed Md Golam, Ghosh Avik W, Kent Andrew D
Center for Quantum Phenomena, Department of Physics, New York University, New York, NY, 10003, USA.
Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904, USA.
Adv Sci (Weinh). 2021 Sep;8(18):e2100481. doi: 10.1002/advs.202100481. Epub 2021 Aug 2.
Ferrimagnetic thin films are attractive for low-power spintronic applications because of their low magnetization, small angular momentum, and fast spin dynamics. Spin orbit torques (SOT) can be applied with proximal heavy metals that also generate interfacial Dzyaloshinskii-Moriya interactions (DMI), which can stabilize ultrasmall skyrmions and enable fast domain wall motion. Here, the properties of a ferrimagnetic CoGd alloy between two heavy metals to increase the SOT efficiency, while maintaining a significant DMI is studied. SOT switching for various capping layers and alloy compositions shows that Pt/CoGd/(W or Ta) films enable more energy-efficient SOT magnetization switching than Pt/CoGd/Ir. Spin-torque ferromagnetic resonance confirms that Pt/CoGd/W has the highest spin-Hall angle of 16.5%, hence SOT efficiency, larger than Pt/CoGd/(Ta or Ir). Density functional theory calculations indicate that CoGd films capped by W or Ta have the largest DMI energy, 0.38 and 0.32 mJ m , respectively. These results show that Pt/CoGd/W is a very promising ferrimagnetic structure to achieve small skyrmions and to move them efficiently with current.
亚铁磁性薄膜因其低磁化强度、小角动量和快速的自旋动力学，在低功耗自旋电子学应用中颇具吸引力。自旋轨道矩（SOT）可通过近端重金属施加，这些重金属还会产生界面Dzyaloshinskii-Moriya相互作用（DMI），该相互作用可稳定超小斯格明子并实现快速的畴壁运动。在此，研究了在两种重金属之间的亚铁磁性CoGd合金的特性，以提高SOT效率，同时保持显著的DMI。对各种覆盖层和合金成分的SOT开关研究表明，与Pt/CoGd/Ir相比，Pt/CoGd/（W或Ta）薄膜能实现更节能的SOT磁化翻转。自旋扭矩铁磁共振证实，Pt/CoGd/W具有16.5%的最高自旋霍尔角，因此SOT效率高于Pt/CoGd/（Ta或Ir）。密度泛函理论计算表明，由W或Ta覆盖的CoGd薄膜具有最大的DMI能量，分别为0.38和0.32 mJ/m²。这些结果表明，Pt/CoGd/W是一种非常有前景的亚铁磁性结构，可用于实现小斯格明子并通过电流有效地移动它们。
