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<30 K. We show that the amplitude of negative magnetoresistance reaches its maximum dR/R~70% at B=54 T, in the vicinity of phase transition occurring in this strongly correlated electron system at T_C~5 K. The crossover from negative magnetoresistance to positive magnetoresistance found at intermediate temperatures at T>30 K 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.