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

J. A. Souza, H. Terashita, E. Granado, R. F. Jardim, N. F. Oliveira, R. Muccillo
2008 Physical Review B  
High-resolution synchrotron x-ray powder diffraction in La 0.7 Ca 0.3 MnO 3 shows in detail a first-order structural phase transition from orthorhombic ͑space-group Pnma͒ to rhombohedral ͑space-group R3c͒ 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
more » ... abatic 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 Ͻ T S to an uncorrelated polaron gas for T Ͼ T S , driven by the change in the crystal symmetry.
doi:10.1103/physrevb.78.054411 fatcat:fp4j53ybzbcstd2ulzbtlvw4wm