Pulsed magnetic field study of the spin gap in intermediate valence compound SmB6

In this work, we report the behavior of electrical resistivity of SmB6 at temperatures between 2.2 and 70 K in pulsed magnetic fields up to 54 T. A strong negative magnetoresistance was detected with increasing magnetic field, when lowering the temperature in the range T < 30K. We show that the amplitude of negative magnetoresistance reaches its maximum dR/R similar to 70% at B = 54 T, in the vicinity of phase transition occurring in this strongly correlated electron system at T-c similar to 5 K. The crossover from negative magnetoresistance to positive magnetoresistance found at intermediate temperatures at T>30K is discussed within the framework of exciton-polaron model of local charge fluctuations in SmB6 proposed by Kikoin and Mishchenko. It seems that these exciton-polaron in-gap states are influenced both by temperature and magnetic field. (C) 2009 Elsevier B.V. All rights reserved.status: publishe