Origins of colossal magnetoresistance in perovskite-type manganese oxides

Phenomena of colossal magnetoresistance (MR) or magnetic field induced insulator-metal (I-M) transitions have been investigated for single crystals of perovskite-type manganese oxides with controlled carrier density and one-electron bandwidth. In addition to the canonical MR behavior near the Curie temperature, the first-order phase transition accompanying several orders of magnitude change in resistivity has been observed under an external magnetic field for many of the composition-controlled crystals as an intrinsic bulk phenomenon. It was proved by the systematic experimental investigations that the field-induced destruction of the charge-ordered state accompanying the lattice structural as well as metamagnetic transition is a major origin of such a colossal MR. Versatile MR phenomena and I-M phase diagrams in the T-H plane are presented with their interpretation. (C) 1996 American Institute of Physics.