Polaron liquid-gas crossover at the orthorhombic-rhombohedral transition of manganites

Autor(es)

Souza, J. A. ; Terashita, H. ; Granado, E. ; Jardim, R. F. ; Oliveira, N. F., Jr. ; Muccillo, R.

• Tipo de documento: Artigo Científico
• Fonte: PHYSICAL REVIEW B; v. 78, n. 5, p. 7-pg., 2008-08-01.

Resumo

High-resolution synchrotron x-ray powder diffraction in La0.7Ca0.3MnO3 shows in detail a first-order structural phase transition from orthorhombic (space-group Pnma) to rhombohedral (space-group R (3) over barc) crystal structures near T-S=710 K. Magnetic susceptibility measurements show that the rhombohedral phase strictly obeys the Curie-Weiss law as opposed to the orthorhombic phase. A concomitant change in the electrical resistivity behavior, consistent with an alteration from nonadiabatic to adiabatic small polaron hopping regimes, was also observed at T-S. The simultaneous change in transport and magnetic properties are identified as a transition from a correlated polaron liquid for T<T-S to an uncorrelated polaron gas for T>T-S, driven by the change in the crystal symmetry. (AU)

• Processo FAPESP: 07/01039-7 - Estudo do comportamento critico de transicoes de fase em sistemas com propriedades magneticas, eletronicas e estruturais fortemente correlacionadas.
• Beneficiário: José Antonio Souza
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 02/01856-1 - Separacao de fase e magnetorresistencia em manganitas.
• Beneficiário: José Antonio Souza
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 05/53241-9 - Estudo de fenômenos intergranulares em materiais cerâmicos
• Beneficiário: Reginaldo Muccillo
• Modalidade de apoio: Auxílio à Pesquisa - Temático