Abstract
The magnetic properties and magnetoresistance of Pr0.7Pb0.3MnO3 single crystals have been studied. At low temperature, the temperature dependence of magnetization can be represented as M(T) = M(0)(1-BT3/2). A large B value was observed. The spontaneous magnetic moment is slightly larger than the spin-only value for Mn3+ and Mn4+ ions. Above the Curie temperature, the susceptibility obeys the Curie-Weiss Law and the resistivity R can fit well with R0exp (T0/T)1/4. It is found that the effective paramagnetic moment obtained from the Curie constant is larger than the theoretical value. The large effective paramagnetic moment may originate from the magnetic clusters. A large low-field magnetoresistance of ΔR/R(0) = -50% is observed at 230 K in 1 T.