Effect hyperthermia in CoFe₂O₄@MnFe₂O₄ nanoparticles studied by using field-induced Mössbauer spectroscopy

CoFe₂O₄@MnFe₂O₄, with a mixed core-shell structure was fabricated by a high temperature thermal decomposition. From the Rietveld refinement, these nanoparticles were found to be cubic spinel with space group Fd-3m and with a Bragg factor (R _B) and a structure factor (R _F) less than 5%. The size and the shape of the nanoparticles were examined with high-resolution transmission electron microscopy (HR-TEM). The values of the magnetization (M _S) and the coercivity (H _C) of these nanoparticles at room temperature were 78.95 emu/g and 21.2 mT, respectively. The effect of hyperthermia, measured with a magneTherm device showed that the self-heating temperature of the nanoparticles could reach 133 °C. To determine the applicability of nanoparticles in hyperthermia therapy, we evaluated the in-vitro cell viability of nanoparticles. Based on the probability distribution of cations, we determined the Mössbauer spectra at 4.2 K with two sets of six lines under various applied fields parallel to the direction of the γ-rays. To separate the A and the B sites, we also obtained the Mössbauer spectra of the nanoparticles under high external field up to 5 T at 4.2 K. From the detailed analysis of the Mössbauer spectra, the spin canting angles and the anisotropy energies at the A and the B sites were determined.