Magnetic properties of bi-, tri- and multicrystals of 3D topological insulator Bi1−x–Sbx (0.06≤ x ≤0.2)

Abstract

The magnetic properties of bi-, tri- and multicrystals of 3D topological insulator Bi1−xSbx (0.06<x<0.22) were studied in the temperature range 1.6–300 K and fields up to 70 kOe using an SQUID magnetometer. Two superconducting phases associated with adjacent and central layers of the crystallite interfaces of the bicrystals are identified. It has been found that due to the different stress structure the transition temperature Tc for one superconducting phase changes considerably, from 8.3 to 36 K, while for another superconducting phase, Tc remains within the range 3.7–4.6 K. In tricrystals and bicrystals with high contents of structural disorder and topological defects, ferromagnetic hysteresis loops and magnetic field expulsion have been observed simultaneously.