Size effects on charge ordering and magnetic properties in La0.25Ca0.75MnO3

The size effects on the charge ordering (CO) and magnetic properties in La_0.25Ca_0.75MnO₃ with mean particle size ranging from 40 to 2000 nm were studied. With decreasing particle size the CO transition temperature shifts to lower temperature and the transition width becomes increasingly wide, indicating the weakening of the CO state. Meanwhile the ferromagnetic (FM) cluster glass state appears and the magnetization at low temperature increases significantly. The behaviour is due to the increasing uncompensated surface spins which weaken the antiferromagnetic interaction and disfavour the formation of the CO state. The suppression of the CO state and appearance of the FM cluster glass state are also found in La_0.25Ca_0.75MnO₃ nanowires fabricated by a sol–gel template method. These results indicate that the CO state can be modulated effectively by varying particle size, which has an important implication for nano-device applications of manganites.