Cui Zhangzhang, Grutter Alexander J, Zhou Hua, Cao Hui, Dong Yongqi, Gilbert Dustin A, Wang Jingyuan, Liu Yi-Sheng, Ma Jiaji, Hu Zhenpeng, Guo Jinghua, Xia Jing, Kirby Brian J, Shafer Padraic, Arenholz Elke, Chen Hanghui, Zhai Xiaofang, Lu Yalin
Hefei National Laboratory for Physical Sciences at the Microscale, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China.
Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Sci Adv. 2020 Apr 10;6(15):eaay0114. doi: 10.1126/sciadv.aay0114. eCollection 2020 Apr.
Engineering magnetic anisotropy in two-dimensional systems has enormous scientific and technological implications. The uniaxial anisotropy universally exhibited by two-dimensional magnets has only two stable spin directions, demanding 180° spin switching between states. We demonstrate a previously unobserved eightfold anisotropy in magnetic SrRuO monolayers by inducing a spin reorientation in (SrRuO)/(SrTiO) superlattices, in which the magnetic easy axis of Ru spins is transformed from uniaxial 〈001〉 direction ( < 3) to eightfold 〈111〉 directions ( ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO. First-principle calculations reveal that increasing the SrTiO layer thickness induces an emergent correlation-driven orbital ordering, tuning spin-orbit interactions and reorienting the SrRuO monolayer easy axis. Our work demonstrates that correlation effects can be exploited to substantially change spin-orbit interactions, stabilizing unprecedented properties in two-dimensional magnets and opening rich opportunities for low-power, multistate device applications.
在二维系统中设计磁各向异性具有巨大的科学和技术意义。二维磁体普遍表现出的单轴各向异性只有两个稳定的自旋方向，这要求在不同状态之间进行180°的自旋切换。我们通过在（SrRuO）/（SrTiO）超晶格中诱导自旋重新取向，展示了磁性SrRuO单层中一种以前未观察到的八重各向异性，其中Ru自旋的磁易轴从单轴〈001〉方向（<3）转变为八重〈111〉方向（≥3）。这种八重各向异性使得SrRuO单层中能够实现71°和109°的自旋切换，类似于铁电BiFeO中的71°和109°极化切换。第一性原理计算表明，增加SrTiO层的厚度会诱导出一种由关联驱动的轨道有序化，调节自旋-轨道相互作用并重新定向SrRuO单层的易轴。我们的工作表明，可以利用关联效应来显著改变自旋-轨道相互作用，在二维磁体中稳定前所未有的特性，并为低功耗、多态器件应用开辟丰富的机会。
