Neutron diffraction evidence for a new ferromagnetic phase in Cr doped Pr0.5Ca0.5MnO3

Abstract

Cr doping in ${\mathrm{Pr}}_{\mathrm{0.5}}{\mathrm{Ca}}_{\mathrm{0.5}}{\mathrm{MnO}}_{\mathrm{3}}$ is known to destroy the low-temperature antiferromagnetic charge-ordered state and to induce a ferromagnetic component as well as colossal magnetoresistance properties. Effects of Cr doping on the magnetic and nuclear structures are studied here by neutron diffraction for ${\mathrm{Pr}}_{\mathrm{0.5}}{\mathrm{Ca}}_{\mathrm{0.5}}{\mathrm{Mn}}_{\mathrm{0.95}}{\mathrm{Cr}}_{\mathrm{0.05}}{\mathrm{O}}_{\mathrm{3}}.$ It is shown that, at low temperature, the strongly distorted charge ordered structure usually observed in ${\mathrm{Pr}}_{\mathrm{0.5}}{\mathrm{Ca}}_{\mathrm{0.5}}{\mathrm{MnO}}_{\mathrm{3}}$ is replaced by a ferromagnetic phase in which the basal-plane distortion of the ${\mathrm{MnO}}_{\mathrm{6}}$ octahedra has disappeared, in agreement with the restoration of the double–exchange interactions.