Spin Dependent Hopping and Colossal Negative Magnetoresistance in EpitaxialNd0.52Sr0.48MnO3Films in Fields up to 50 T

Abstract
The low carrier mobility of the magnetic perovskite Nd0.52Sr0.48MnO3 implies that the dominant conductivity mechanism is related to Mott hopping. We propose a modification of Mott's original model by taking into account that the hopping barrier depends on the misorientation between the spins of electrons at an initial and a final state in an elementary hopping process. Using this model we deduce a negative-magnetoresistivity scaling proportional to the Brillouin function B in the ferromagnetic state and to B2 in the paramagnetic state. Both predictions are in full agreement with the magnetoresistivity measured in pulsed magnetic fields up to 50 T.