Suppression of charge order, disappearance of antiferromagnetism, and emergence of ferromagnetism in Nd0.5 Ca0.5 MnO3 nanoparticles

Abstract

Nd0.5 Ca0.5 MnO3 nanoparticles (average diameter ∼20 and 40 nm) are synthesized by the polymeric precursor sol-gel method and characterized by various physico-chemical techniques. Quite strikingly, in the 20 nm particles, the charge-ordered (CO) and the antiferromagnetic phases observed in the bulk below 250 K and 160 K, respectively, are completely absent. Instead, a ferromagnetic (FM) transition is observed at 95 K followed by an insulator-to-metal transition at 75 K. The 40 nm particles show a residual CO phase but a transition to the FM state also occurs, at a slightly higher temperature of 110 K. © 2006 The American Physical Society.