Size-induced ferromagnetism and metallicity in Nd0.5Sr0.5MnO3 nanoparticles: A neutron diffraction study

The phenomenon of destabilization of antiferromagnetic insulating state into a ferromagnetic metallic one in Nd0.5Sr0.5MnO3 with the variation of particle/grain size is critically investigated. Based on our neutron diffraction study, magnetic and transport experiments, we observe ferromagnetism and metallic behavior in Nd0.5Sr0.5MnO3 (similar to 40 nm grain size) as against A-type antiferromagnetic order in the sample with the largest grain size (similar to 800 nm). The latter shows a systematic change in the lattice parameters with temperature, and an antiferromagnetic ground state similar to that of a bulk system. Interestingly, the sample with the smallest grain sizes exhibits insignificant structural changes (compared to the largest grain size sample) but a complete change in the magnetic state (ferromagnetic behavior) as revealed from the neutron diffraction study. Magnetic measurements also confirm a ferromagnetic state in the small-grained sample. Electronic transport measurements exhibit a metal-insulator transition in this sample. The effects are primarily attributed to enhanced surface disorder. (C) 2011 Elsevier B.V. All rights reserved.