Ferromagnetism at room temperature in La–Ba–Ca–Mn–O thin films

Abstract

The effects of substitution of Ca by Ba in La1−xCaxMnO3 (LCMO) with x<0.5 were investigated systematically in order to clarify the role of the size of the A cations. As for the La1−x(Ba–Ca)xMnO3 (LBCMO) films of ferromagnetic metallic (FMM) region (x=0.2; 0.3; and 0.4), by doping Ba, the ferromagnetic transition temperature (TC) and the insulator-to-metal (IM) transition temperature (TIM) were improved about 30–60 K, compared with those of LCMO thin films with the same ratio of Mn3+:Mn4+. Especially, La0.7Ba0.1Ca0.2MnO3 thin films have an anomalously high TC (about room temperature) and a TIM of 275 K under zero field. In the ferromagnetic insulating (FMI) region (x=0.15; 0.1), the Ba doping enables the IM transition and remarkably heightens the TC as well. The phase diagram shows that in the slightly doped region (x<0.5), Ba doping has made the FMM phase significantly expanded.