Induction of magnetodielectric coupling in multiferroic lanthanum ferrite by cobalt doping

Abstract

This research focuses on studying the magnetodielectric coupling at room temperature in lanthanum ferrite induced by cobalt substituting iron sites. The study involved varying cobalt content from 0 to 0.1 mol, with samples synthesized via high-energy ball milling. The evolution of crystal structure, dielectric, and magnetic properties was analyzed. X-ray diffraction (XRD) and Rietveld refinement confirmed the orthorhombic single-phase structure with the Pnma space group in the doped lanthanum ferrite. Vibrating-sample magnetometry results demonstrated that cobalt doping alters the antiferromagnetic order of lanthanum ferrite, inducing ferromagnetism, with a maximum specific magnetization of 1.25 emu/g observed at 0.075 mol cobalt content. Scanning electron microscopy (SEM) analysis revealed an increase in grain size with higher cobalt content, which impacts the material's electrical and dielectric properties. The doped ferrites exhibited lower relative permittivity values compared to pure LaFeO₃. Additionally, the presence of cobalt reduced the dielectric dissipation factor, attributed to minor crystal structure distortions. Notably, magnetodielectric coupling was observed in these multiferroic materials for the first time, evidenced by changes in relative permittivity under varying applied fields and frequencies. The highest magnetodielectric coupling was achieved at 0.025 mol cobalt doping, with relative permittivity values ranging from 70 to 26 across frequencies from 50 to 1000 Hz. These findings confirm that cobalt-doped lanthanum ferrites exhibit magnetodielectric coupling at room temperature, suggesting potential for expanded technological applications.