Electronic Transport and Magnetic Properties in Ferroelectric-Ferromagnetic Composites La_5/8Ca_3/8MnO₃:ErMnO₃

The crystal structures and electronic transport properties of composites, xLa_5/8Ca_3/8MnO₃:ErMnO₃:(1-x)ErMnO₃(x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1), where ErMnO₃ is the insulating ferroelec-tric and La_5/8Ca_3/8MnO₃ is the metallic ferromagnetic component, were studied. The magnetization of samples (x=0, 0.5, 1) were also measured as a function of temperature from 4 K to 300 K. The X-ray diffraction data show La_5/8Ca_3/8MnO₃ and ErMnO₃ are almost complete immiscible, originating from the significant difference in their crystal structures. All the composites show a metal-insulator transition when the molar fraction of xLa_5/8Ca_3/8MnO3 component x≥0.4 and the electronic transport behaviors follow the classical percolation theory model very well. Magnetization of the mixture with x=0.5 is unique and enhanced greatly compared with that of pure ErMnO₃. Comprehensive analysis of the electronic transport and magnetic results suggests that this material system is a new kind of multiferroic with stronger magnetism in a wider temperature range compared with the single phase multiferroic ErMnO₃.