Magnetic susceptibility of Bi2Te3-Sb2Te3 alloys

The magnetic susceptibility of Czochralski-grown single crystals of Bi2Te3-Sb2Te3 alloys containing 0, 10, 25, 40, 50, 60, 65, 70, 80, 90, 99.5, or 100 mol % Sb2Te3 has been investigated. The magnetic susceptibility of these crystals was determined at the temperature T = 291 K and the magnetic field H oriented parallel (chi(parallel to)) and perpendicularly (chi(perpendicular to)) to the trigonal crystallographic axis C (3). A complicated concentration dependence of the anisotropy of magnetic susceptibility chi(parallel to)/chi(perpendicular to) has been revealed. The crystals with the free carrier concentration p approximate to 5 x 10(19) cm(-3) do not exhibit anisotropy of magnetic susceptibility. The transition to the isotropic magnetic state occurs for the compositions characterized by a significantly increased (from 200 to 300 meV) optical bandgap.