Magnetic and magnetotransport studies on ternary topological insulator GeBi_4Te_7

摘要

Temperature and magnetic field dependence of the transport and magnetic properties of ternary topological insulator GeBi_4Te_7 have been studied. Magnetization data shows that the sample remains diamagnetic from 300 K down to 2.5 K whereas, resistivity decreases as temperature decreases and reaches a minimum at 210 K. It increases furtherand attains a maximum at 124 K and then decreases upon reducing the temperature. R (T) measured at 0-15 T shows positive magnetoresistance (MR). The calculated MR % at % <5 K is ～60 %, and it decreases drastically as temperature increases. At T < 124 K, the density of charge carriers (electrons) deduced from Hall measurements is about ～10~(19) cm~(-3) and it increases by one order upon increasing the temperature to 300 K. The lowering of Dirac point due to the lattice distortion caused by the defects at Bi/Ge sites and pinning of Fermi energy deep into the conduction band is believed to cause the observed non-topological signatures in electronic transport properties.