Nature of the diamagnetic maximum in the temperature dependences of the magnetic susceptibility of crystals of (Bi2 − x Sb x )Te3 alloys (0 < x < 1)

Abstract

The temperature dependences of the magnetic susceptibility χ of crystals of (Bi2 − xSbx)Te3 alloys (0 < x < 1) are studied using a SQUID magnetometer in the temperature range from 2 to 400 K with the parallel and perpendicular orientations of the vector of magnetic field strength H relative to the trigonal axis of the crystal C3 (H ‖ C3 and H ⊥ C3). It is found that the diamagnetic susceptibility of the samples with x = 0.2 (Bi1.8Sb0.2Te3) and x = 0.5 (Bi1.5Sb0.5Te3) increases in the range from 50 K to temperatures preceding the emergence of intrinsic conductivity (250 K). It is found that the diamagnetic maximum manifests itself in the same temperature range, in which an anomalous increase in the Hall coefficient is observed. It is shown that the nature of the diamagnetic maximum is associated with the nonparabolicity of the energy spectrum of light diamagnetic holes, a decrease in whose concentration is accompanied by a decrease in their effective masses, which provides an increase in the diamagnetic susceptibility with increasing temperature. These results are confirmed by the dynamics of the temperature variation in the resonance frequency of plasma oscillations of free charge carriers.