Chromium-Induced Ferromagnetism with Perpendicular Anisotropy in Topological Crystalline Insulator SnTe (111) Thin Films

TL;DR

This study demonstrates the induction of ferromagnetism with perpendicular anisotropy in Cr-doped SnTe (111) thin films, highlighting their potential for realizing high-Chern-number quantum anomalous Hall states through chemical potential tuning.

Contribution

It reports the growth and magnetic characterization of Cr-doped SnTe (111) thin films exhibiting ferromagnetism with perpendicular anisotropy, suggesting pathways to achieve quantum anomalous Hall states.

Findings

Cr-doped SnTe films show ferromagnetic order with Curie temperature ~110 K.

Hall measurements indicate long-range ferromagnetism with perpendicular anisotropy.

Anomalous Hall resistance is lower than the quantized value, indicating potential for tuning into QAH state.

Abstract

Topological crystalline insulator (TCI) is a recently-discovered topological phase of matter. It possesses multiple Dirac surface states, which are protected by the crystal symmetry. This is in contrast to the time reversal symmetry that is operative in the well-known topological insulators. In the presence of a Zeeman field and/or strain, the multiple Dirac surface states are gapped. The high-Chern-number quantum anomalous Hall (QAH) state is predicted to emerge if the chemical potential resides in all the Zeeman gaps. Here, we use molecular beam epitaxy to grow 12 double layer (DL) pure and Cr-doped SnTe (111) thin film on heat-treated SrTiO3 (111) substrate using a quintuple layer of insulating (Bi0.2Sb0.8)2Te3 topological insulator as a buffer film. The Hall traces of Cr-doped SnTe film at low temperatures display square hysteresis loops indicating long-range ferromagnetic order with perpendicular anisotropy. The Curie temperature of the 12DL Sn0.9Cr0.1Te film is ~ 110 K. Due to the chemical potential crossing the bulk valence bands, the anomalous Hall resistance of 12DL Sn0.9Cr0.1Te film is substantially lower than the predicted quantized value (~1/4 h/e2). It is possible that with systematic tuning the chemical potential via chemical doping and electrical gating, the high-Chern-number QAH state can be realized in the Cr-doped SnTe (111) thin film.