Competition between coexisting phases in (La,Pr)CaMnO3 manganites

Polycrystalline La5/8-yPryCa3/8MnO3, 0 <= y <= 0.625, samples were synthesized by the solid-state reaction method and studied using x-ray powder diffraction, magnetic susceptibility [chi(T)], and magnetoresistivity [rho(T,H)] measurements. Some features such as an appreciable thermal hysteresis observed in both rho(T) and chi(T) curves indicated a competing scenario due to the coexistence of different phases. We have also found that there is a critical region in the phase diagram, for the Pr concentration ranging from similar to 0.30 to 0.40, where the magnitude of the insulator to metal transition temperature (T-MI), the Curie temperature (T-C), the magnetoresistance, and the residual resistivity (rho(0)) are characterized by abrupt changes with little increase in y. Our data also indicate that the physical properties of these manganites in this critical region are dominated by a strong competition between coexisting ferromagnetic metallic and charge-ordered insulating phases. (C) 2007 American Institute of Physics.