Highly Tunable Beyond-Room-Temperature Intrinsic Ferromagnetism in Cr-Doped Topological Crystalline Insulator SnTe Crystals

The combination of topological phase and intrinsic beyond-room-temperature ferromagnetism is expected to realize the quantum anomalous Hall effect at a high temperature. However, no beyond-room-temperature intrinsic ferromagnetism has been reported in either topological insulator or topological crystalline insulator (TCI) so far. Here, we report Cr-doping in TCI-phase SnTe crystals which possess highly tunable beyond-room-temperature intrinsic ferromagnetism including T_c, magnetic moment, and coercivity by varying Cr contents and crystal thickness. With the increase of the Cr content, the T_c increases by 159 K from 221 to 380 K and the saturation magnetic moments increase by ∼23.6 times from 0.018 to 0.421 μ_B/f.u. This intrinsic beyond-room-temperature ferromagnetism is fully demonstrated by the anomalous Hall effect and magneto-optical Kerr effect in a single Cr_xSn_1-xTe nanosheet. Moreover, the room-temperature tunneling magnetoresistance effect has been realized by using a Cr_xSn_1-xTe flake, a Fe thin film, and a commercially compatible ultrathin AlO_x tunneling barrier. This work indicates a great potential of Cr_xSn_1-xTe crystals in room-temperature magnetoelectronic and spintronic devices.