Phase separation and destabilization of the charge-ordered state in Cr-doped manganites

Destabilization of the charge-ordered (CO) state in half-doped manganites by chromium (Cr) doping in the manganese (Mn) sites was investigated. The Cr doping in the half-doped manganites makes the CO state short-ranged and induces new ferromagnetic metallic (FMM) phase at low temperature. Real space images taken in the CO state by electron microscope clearly show coexistence of the short-ranged CO and FMM states, which is characterized as a microscopicscale phase separation. Furthermore, the CO state in the Cr-doped manganites has a superlattice structure with the incommensurate wave vector q = (1/2 - ε)a*_o, where ε depends on the Cr concentration. These results suggest that the Cr doping suppresses the incommensurate to commensurate structural transition found in the half-doped manganites and produces new FMM phase.