Insights on the Heating Characteristics of Mn and Co Ferrites

The heating characteristics of ferrite nanoparticles are inconsistent due to various factors that affect the optimum particle size required for maximum power dissipation. The heating mechanism of Fe3O4, MnFe2O4, and Co0.5Fe2.5O4 in the size range 10–40 nm with varying particle size distribution is correlated with the effective specific absorption rate (ESAR). The effective magnetic anisotropy of the ferrite samples determined using electron spin resonance is between 11.8 and 24.8 kJ· m−3. The thermal profiles of Fe3O4, MnFe2O4, and Co0.5Fe2.5O4 are probed employing infrared thermography where the measured ESAR is between 1.74 and 3.16 nHm2·kg−1. The theoretical ESAR of 16.63 and 9.19 nHm2·kg−1 are obtained for the Co substituted Fe3O4 and MnFe2O4, respectively, for an average size of 40 nm. The analysis of particle size distributions in combination with theoretical estimations gives the percentage of particles contributing to the power dissipation as 80 % for narrow dispersion and 45 % for broad dispersion deviating from the predicted optimum size range. In addition to ascertaining the functioning regime of the linear response theory, an increase in ESAR with decreasing anisotropy energy is observed. The discrepancy between the simulations and experimentations is prudently examined, taking the intrinsic as well as extrinsic parameters into account.