First order nucleation of charge ordered domains in La0.5Ca0.5MnO3 detected by 139La and 55Mn NMR

The local magnetism and charge ordering of La0.5Ca0.5MnO3, was investigated between room temperature and 1.3 K by means of La-139 and Mn-55 NMR. Antiferromagnetic and ferromagnetic domains are assigned unambiguously to the insulating charge ordered and the metallic state respectively. The phases are found to coexist at all temperatures below the first formation of a charge-ordered state. The two signal fractions display thermal and magnetic hysteresis, while their local fields and relaxations do not. These features and the absence of any critical behavior are characteristic of a first order F-AF transition, with ferromagnetic domains microscopically identical to the bulk metallic phase of the OMR manganite. [S0031-9007(98)07678-9].