Correlation-driven eightfold magnetic anisotropy in a two-dimensional oxide monolayer

Zhangzhang Cui; Alexander J Grutter; Hua Zhou; Hui Cao; Yongqi Dong; Dustin A Gilbert; Jingyuan Wang; Yi-Sheng Liu; Jiaji Ma; Zhenpeng Hu; Jinghua Guo; Jing Xia; Brian J Kirby; Padraic Shafer; Elke Arenholz; Hanghui Chen; Xiaofang Zhai; Yalin Lu

doi:10.1126/sciadv.aay0114

Correlation-driven eightfold magnetic anisotropy in a two-dimensional oxide monolayer

Sci Adv. 2020 Apr 10;6(15):eaay0114. doi: 10.1126/sciadv.aay0114. eCollection 2020 Apr.

Authors

Zhangzhang Cui^{1

2}, Alexander J Grutter³, Hua Zhou⁴, Hui Cao^{1

2

4}, Yongqi Dong^{1

4}, Dustin A Gilbert^{3

5}, Jingyuan Wang⁶, Yi-Sheng Liu⁷, Jiaji Ma⁸, Zhenpeng Hu⁹, Jinghua Guo⁷, Jing Xia⁶, Brian J Kirby³, Padraic Shafer⁷, Elke Arenholz^{7

10}, Hanghui Chen^{8

11

12}, Xiaofang Zhai^{1

2

13}, Yalin Lu^{1

2}

Affiliations

¹ Hefei National Laboratory for Physical Sciences at the Microscale, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China.
² Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
³ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
⁴ Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA.
⁵ Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA.
⁶ Department of Physics, University of California, Irvine, Irvine, CA 92697, USA.
⁷ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁸ NYU-ECNU Institute of Physics, NYU Shanghai, Shanghai 200122, China.
⁹ School of Physics, Nankai University, Tianjin 300071, China.
¹⁰ Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY 14853, USA.
¹¹ State Key Laboratory of Precision Spectroscopy, School of Physical and Material Sciences, East China Normal University, Shanghai 200062, China.
¹² Department of Physics, New York University, New York, NY 10027, USA.
¹³ School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.

Abstract

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 SrRuO₃ monolayers by inducing a spin reorientation in (SrRuO₃)₁/(SrTiO₃) _N superlattices, in which the magnetic easy axis of Ru spins is transformed from uniaxial 〈001〉 direction (N < 3) to eightfold 〈111〉 directions (N ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO₃ monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO₃. First-principle calculations reveal that increasing the SrTiO₃ layer thickness induces an emergent correlation-driven orbital ordering, tuning spin-orbit interactions and reorienting the SrRuO₃ 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.

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