Anomalous Hall effect and magnetoresistance in Nd_(1-x)Sr_(x)MnO_(3) single crystals

摘要

We have investigated Hall-effect and magnetotransport properties of Nd-based manganite crystals with controlled band filling. We have determined normal (R_(H)) and anomalous (R_(S)) Hall coefficients as a function of temperature in the ferromagnetic metallic crystal. The obtained effective carrier number (1/eR_(H)) is about 1.0 hole/Mn site, which does not depend on temperature and nominal hole concentration. We have also found magnetoresistance (MR) in the over-doped samples showing various electronic, magnetic, and orbital structures. In C-type antiferromagnetic insulator (0.63≤x), the ρ-T curve below 45 K is well explained by the variable-range hopping (VRH) mechanism. A large negative MR, which is increased with decreasing temperature, was observed in VRH region. The localization length from the characteristic temperature of VRH increases with magnetic field, which indicates that application of magnetic field induces a reduction of energy gap from E_(F) to the mobility edge by the Zeeman shift.