NEUTRON-DIFFRACTION STUDY OF THE MAGNETIC-FIELD-INDUCED METAL-INSULATOR-TRANSITION IN PR0.7CA0.3MNO3

Without a magnetic field Pr0.7Ca0.3MnO3 exhibits three phase transitions: a change of the lattice symmetry at T-B = 200 K, an antiferromagnetic ordering at T-N= 140 K, and a canted antiferromagnetism at T-CA= 110 K. Although the resistivity of Pr1-xCaxMnO3 shows insulating behavior at zero field, it exhibits an insulator-metal (I-M) transition at around 4.0 T at 5 K. An applied field enforces a ferromagnetic spin alignment and drives Pr1-xCaxMnO3 into the metallic state by actuating the double-exchange mechanism and destroying the charge ordering. This I-M transition at 5 K is accompanied by a large hysteresis.