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arXiv · 1706.07971

Above 400 K Robust Perpendicular Ferromagnetic Phase in a Topological Insulator

Chi Tang·Cui-Zu Chang·Gejian Zhao·Yawen Liu·Zilong Jiang·Chao-Xing Liu·Martha R. McCartney·David J. Smith·Tingyong Chen·Jagadeesh S. Moodera·Jing Shi
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Abstract

The quantum anomalous Hall effect (QAHE) that emerges under broken time-reversal symmetry in topological insulators (TI) exhibits many fascinating physical properties for potential applications in nano-electronics and spintronics. However, in transition-metal doped TI, the only experimentally demonstrated QAHE system to date, the effect is lost at practically relevant temperatures. This constraint is imposed by the relatively low Curie temperature (Tc) and inherent spin disorder associated with the random magnetic dopants. Here we demonstrate drastically enhanced Tc by exchange coupling TI to Tm3Fe5O12, a high-Tc magnetic insulator with perpendicular magnetic anisotropy. Signatures that the TI surface states acquire robust ferromagnetism are revealed by distinct squared anomalous Hall hysteresis loops at 400 K. Point-contact Andreev reflection spectroscopy confirms that the TI surface is indeed spin-polarized. The greatly enhanced Tc, absence of spin disorder, and perpendicular anisotropy are all essential to the occurrence of the QAHE at high temperatures.

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Chi Tang, Cui-Zu Chang, Gejian Zhao, Yawen Liu, Zilong Jiang, Chao-Xing Liu, Martha R. McCartney, David J. Smith, Tingyong Chen, Jagadeesh S. Moodera, Jing Shi. 2017-06-24. Above 400 K Robust Perpendicular Ferromagnetic Phase in a Topological Insulator. https://doi.org/10.1126/sciadv.1700307 10.1126/sciadv.1700307 10.1126/sciadv.1700307

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