Ferromagnetism in Cr-doped topological insulator TlSbTe₂

We have synthesized a new ferromagnetic topological insulator by doping Cr to the ternary topological-insulator material TlSbTe₂. Single crystals of Tl_1-xCr_xSbTe₂ were grown by a melting method and it was found that Cr can be incorporated into the TlSbTe₂ matrix only within the solubility limit of about 1%. The Curie temperature θ_C was found to increase with the Cr content but remained relatively low, with the maximum value of about 4 K. The easy axis was identified to be the c-axis and the saturation moment was 2.8 μ_B (Bohr magneton) at 1.8 K. The in-plane resistivity of all the samples studied showed metallic behavior with p-type carriers. Shubnikov-de Hass oscillations were observed in samples with the Cr-doping level of up to 0.76%. We also tried to induce ferromagnetism in TlBiTe₂ by doping Cr, but no ferromagnetism was observed in Cr-doped TlBiTe₂ crystals within the solubility limit of Cr which turned out to be also about 1%.