Temperature- and frequency-activated semiconductor-to-metal transition in soft ferromagnetic Li0.5Mn0.5Fe2O4 ferrite

Abstract

We prepared Li0.5Mn0.5Fe2O4 ferrite through chemical reaction in a highly acidic solution and the subsequent sintering of the chemical routed powder at temperatures ≧̸800 °C. Surface morphology showed a plastoferrite character for a sintering temperature >1000 °C. The mechanical softening of metal–oxygen bonds at higher measurement temperatures stimulated a delocalization of charge carriers, which were strongly localized in the A and B sites of the spinel structure at lower temperatures. The charge delocalization process activated a semiconductor-to-metal transition in the ac conductivity curves, obeyed by the Jonscher power law and Drude equation. A metallic state is also confirmed by the frequency dependence of the dielectric constant curves.