Formation of charge ordering and complex magnetic properties in the (Bi,Ca)Mn1-xCrxO3

In this paper, two series samples, Bi0.6Ca0.4Mn1-xCrxO3 (Bi-rich, 0⩽x⩽0.05), and Bi0.24Ca0.76Mn1-xCrxO3 (Bi-poor, 0⩽x⩽0.24) are investigated by means of resistivity, magnetization and electron-spin-resonance. The formation process of charge ordering is studied. The evolution of charge ordering with Cr content is drastically different between Bi-rich and Bi-poor samples. Charge ordering “melts” gradually with increasing Cr content in Bi-rich system while “collapses” when x⩾0.03 in Bi-poor series. These results are understood by considering the evolution of the Mn3+/Mn4+ ratio with Cr doping in different systems. Complex magnetic properties are observed in Bi-poor series with the doping level increasing from zero to 0.24. These behaviors are discussed in the context of phase separation scenario.