Colossal magnetoresistance and magnetic phase transitions in bulk Nd0.7Ba0.3MnO3

Perovskite-type Nd(0.7)Bao(0.3)MnO(3) has been synthesized and its magnetic and magnetotransport properties studied in the temperature range from 5 K to 300 K. X-ray diffraction indicates that the crystal-symmetry is orthorhombic with a=0.5508(1) nm, b=0.5496(2) nm, and c=0.7764(3) nm. There exist two magnetic phase transitions. It first undergoes a paramaganetic-to-ferromagnetic phase transition at Curie temperature, T-C=115 K, and then partial ordering of Nd magnetic moments develops at T-Nd=40 K as temperature is further decreased. Resistivity measurements indicate corresponding insulator-to-metal transition near T-C and a reentrant metal-to-insulator transition near 40 K. Colossal magnetoresistance exists over a wide temperature range, MR=[R(H)-R(0)]/R-(0) is over 90% below 120 K. The maximum MR (98%) appears at 95 K, close to the paramagnetic-to-ferromagnetic phase transition.