Controlling the magnetic anisotropy in Cr₂Ge₂Te₆ by electrostatic gating

Electrical control of magnetism in van der Waals ferromagnetic semiconductors is an important step in creating novel spintronic devices, capable of processing and storing information, with these materials. For practical devices, electrical control at or near room temperature is sought, but most layered ferromagnetic semiconductors exhibit Curie temperatures below 100 K. Here, we show that electrostatic gating of thin chromium germanium telluride (Cr2Ge2Te6) crystals can be used to modulate the magnetic phase transition and magnetic anisotropy of this layered ferromagnetic semiconductor and increase its Curie temperature. Using an electric double-layer transistor device, we observe ferromagnetism in the material at temperatures up to 200 K and find that its magnetic easy axis is in the in-plane direction, in contrast to the out-of-plane easy axis of undoped Cr2Ge2Te6. Our analysis suggests that heavy doping promotes a double-exchange mechanism that is mediated by free carriers, which dominates over the superexchange mechanism of the original insulating state.