Phase Separation in CMR Materials: The Role of Spin Nanoclusters

摘要: Manganese perovskites, with the general formula REMnO3 (RE=Rare Earth), display a wealth of new phenomena on substitution part trivalent RE by divalention alcaline earth series (Ca, Sr etc.). This doping results in formation mixed valence system (Mn3+ , Mn4+) rich phase diagram ferromagnetic insulators at low doping, conductors, higher and antiferromagnetic than 50%. The displays magnetic separation boundaries while application field brings its ground state which is usually metallic state. result this process appearance colossal negative magnetoresistance (CMR) many potential applications. There has been an intensive study these systems during past 5 years order to elucidate phenomenon atomic level. double electron exchange (Zener) Jahn-Teller effect are basic principles governing CMR effect, although there questions that still open. It now established, within relevant scientific community, arise from interplay charge, moment (spin orbital) lattice degrees freedom. Among experimental techniques have employed for studies, spectroscopic hyperfine interaction studies prime interest since they provide information In work, we present Moessbauer La0.5Ca0.5MnO3 doped 1% 57Fe 119Sn. These show coexistence phases, particular close boundaries, dynamic transformation one other role spin-nanoclusters transformation.