Huang Zhaocong, Liu Wenqing, Yue Jinjin, Zhou Qionghua, Zhang Wen, Lu Yongxiong, Sui Yunxia, Zhai Ya, Chen Qian, Dong Shuai, Wang Jinlan, Xu Yongbing, Wang Baoping
Department of Physics, Jiangsu Key Laboratory for Advanced Metallic Materials, Southeast University , Nanjing 211189, China.
Spintronics and Nanodevice Laboratory, Department of Electronics, University of York , York, U.K.
ACS Appl Mater Interfaces. 2016 Oct 12;8(40):27353-27359. doi: 10.1021/acsami.6b09478. Epub 2016 Oct 3.
By analyzing the in-plane angular dependence of ferromagnetic resonance linewidth, we show that the Gilbert damping constant in ultrathin FeO epitaxial films on GaAs substrate can be enhanced by thickness reduction and oxygen vacancies in the interface. At the same time, the uniaxial magnetic anisotropy due to the interface effect becomes significant. Using the element-specific technique of X-ray magnetic circular dichroism, we find that the orbital-to-spin moment ratio increases with decreasing film thickness, in full agreement with the increase in the Gilbert damping obtained for these ultrathin single-crystal films. Combined with the first-principle calculations, the results suggest that the bonding with Fe and Ga or As ions and the ionic distortion near the interface, as well as the FeO defects and oxygen vacancies, may increase the spin-orbit coupling in ultrathin FeO epitaxial films and in turn provide an enhanced damping.
通过分析铁磁共振线宽的面内角度依赖性，我们表明，在GaAs衬底上的超薄FeO外延膜中，吉尔伯特阻尼常数可通过减小厚度和界面处的氧空位而增强。同时，由于界面效应导致的单轴磁各向异性变得显著。利用X射线磁圆二色性的元素特异性技术，我们发现轨道与自旋矩之比随膜厚度的减小而增加，这与这些超薄单晶膜中吉尔伯特阻尼的增加完全一致。结合第一性原理计算，结果表明，与Fe和Ga或As离子的键合以及界面附近的离子畸变，以及FeO缺陷和氧空位，可能会增加超薄FeO外延膜中的自旋轨道耦合，进而提供增强的阻尼。
