The Thermal Conductivity and Diffusivity of Mn_xFe_3-xO₄ (0≤x≤1.5) from 200 to 700K

Abstract

The thermal conductivity of Mn_xFe_3-xO₄ with various compositions (x=0, 0.25, 0.5, 0.8, 1.0, 1.5) and hematite, and the thermal diffusivity of Mn_xFe_3-xO₄ (x=0.8, 1.0, 1.5) were measured by means of a scanning temperature method in the temperature range from 200 to 700K. An anomaly of ferrimagnetic transition was observed in the thermal diffusivity measurement for each sample, and the peak temperatures varied with the composition (x=0.8, 1.0, 1.5) were in good agreement with those observed in the permeability measurements. The anomaly was not as clearly observed in the thermal conductivity measurement as in the thermal diffusivity measurement. The measured values for thermal conductivity of Mn_xFe_3-xO₄ were so low that the phonon mean free paths calculated from the thermal conductivity data were comparable with the lattice constant. The thermal conductivity of Mn_xFe_3-xO₄ was strongly dependent on composition x and showed the maxima at the compositions with x=0 and 1.0.