Ferromagnetism in thin-film Cr-doped topological insulator Bi2Se3

We report on the observation of ferromagnetism in epitaxial thin films of the topological insulator compound Bi2Se3 with chromium doping. The structural, magnetic, and magnetoelectrical properties of Bi2Se3 were investigated for Cr concentrations up to 10%. For a Cr content up to ∼5% the films are of good crystalline quality, with the lattice parameter a decreasing and the lattice parameter c increasing with increasing Cr concentration. The Curie temperature reached a maximum TC = 20 K for 5.2% Cr. Well-defined ferromagnetic hysteresis in the magnetization and in the magnetoresistance was also observed in these films.