Effect of size reduction on charge ordering in La_0.5Ca_0.5MnO₃

Abstract

In this paper we report size-induced collapse of charge ordering in nanoparticles of La_0.5Ca_0.5MnO₃ (LCMO). This happens when the particle size ≈100 nm or below. The investigation shows that a tuning of size can tune the nature of ground state in manganites. The particles were synthesized by sol-gel route (polyol based) and were characterized by X-ray-diffraction (XRD) and Transmission Electron Microscope (TEM). The collapse of charge ordering stabilizes the ferromagnetic phase with metallic character. The resulting phase appears to be electronically phase segregated. We base our conclusions on detailed magnetization and resistivity measurements as well as the evolution of the structure on size reduction. The observed data have been explained as arising due to a combined effect of both phases. Size reduction reduces the orthorhombic distortion and enhances the Double exchange that stabilizes the ferromagnetic phase and increases the band width. It is likely that this enhanced band-width leads to weakening of the charge-ordering and its eventual collapse.