Transition Metal Substitutions Induce Ferromagnetism in Bi₂Te₃

The possibilities of magnetism induced by transition-metal atoms substitution in Bi₂Te₃ system are investigated by ab initio calculations. The calculated results indicate that a transition-metal atom substitution for a Bi atom produces magnetic moments, which are due to the spin-polarization of transition-metal 3d electrons. The values of magnetic moments are 0.92, 1.97, 2.97, 4.04, and 4.98 μ_B for 4% Ti-, V-, Cr-, Mn-, and Fe-doped Bi₂Te₃ respectively. When substituting two transition-metal atoms, the characteristics of exchanging couple depend upon the distributions of the Bi atoms substituted. When two transitionmetal atoms substituting for Bi atoms locate at the sites of Bi1 and Bi5, with the distance of 11.52 Å, the Bi_1.84TM_0.16Te₃ system is energetically most stable and exhibits ferromagnetic coupling.