Magnetic and Magnetotransport Studies on Ternary Topological Insulator GeBi4Te7

Temperature and magnetic field dependence of the transport and magnetic properties of ternary topological insulator GeBi4Te7 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 T <50 K is similar to 60 %, and it decreases drastically as temperature increases. At T < 124 K, the density of charge carriers (electrons) deduced from Hall measurements is about similar to 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.