Particle size effects on interplay between charge ordering and magnetic properties in nanosized La_(0.25)Ca)_(0.75)MnO_3

摘要

The charge ordering (CO) and magnetic properties of La_(0.25)Ca_(0.75)MnO_3 compounds with average particle sizes ranging from 40 to 2000 nm have been studied. With decreasing particle size, the CO transition gradually shifts to lower temperature and becomes increasingly wide and weak; meanwhile, the ferromagnetic cluster glass state appears, and the temperature T_G for the appearance of ferromagnetic clusters shows a nonmonoto-nous variation with a maximum at about 100 nm. The magnetization at low temperature shows a relatively complex change with particle size. A core-shell model was proposed to explain these anomalous behaviors, and the temperature-particle size phase diagram of La_(0.25)Ca_(0.75)MnO_3 was established. These results are helpful in deeply understanding the coupling between charge and spin degrees of freedom in manganites.