Microscopic electronic phase separation and metal-insulator transition in Nd0.5Sr0.5MnO3

Microstructure related to the charge ordered (CO) state and metal-insulator (MI) transition in Nd0.5Sr0.5MnO3 was investigated by transmission electro n microscopy. An in situ observation on heating from the CO state revealed a drastic change in the microstructure: the nucleation and growth of the fe rromagnetic (FM) charge disordered regions proceed in the vicinity of the a ntiphase boundaries in the CO regions, which are closely related to the MI transition around 160 K. These transition processes suggest that an abrupt increase in the electronic conductivity during the MI transition is mainly due to the percolation mechanism. Further more, the FM metallic phase is fo und to be characterized by a spatially fine mixture of incommensurate charg e ordered microdomains in the FM charge disordered phase. This result clear ly demonstrates the occurrence of microscopic-scale electronic phase separa tion in the manganese oxides. [S0163-1829(99)02541-2].