Nanocrystalline Spinel Manganese Ferrite MnFe₂O₄: Synthesis, Electronic Structure, and Evaluation of Their Magnetic Hyperthermia Applications

In this paper, nanocrystalline spinel manganese ferrites MnFe₂O₄ (MFO) were synthesised using the co-precipitation method under different conditions and characterised by XRD, TEM, magnetic measurements and also theoretical calculations. Herein, the first-principles calculations and electron density topologic analysis at DFT level, including a comparison on the influence of relativistic effects, were carried out to obtain the geometries and the electronic parameters of the bulk and (100), (110) and (111) surfaces of the MFO structure, for the first time. The magnetisation field curves reveal a superparamagnetic behaviour for all the analysed samples. The saturation magnetisation values were determined to be 56.6, 53.3, and 54.8 emu/g at 300 K, respectively. Furthermore, the aqueous colloids were transferred to organic media to investigate the effect of particle size and aggregation degrees on the heating efficiency of the nanoparticles. Our findings demonstrate that the MFO spinel nanocrystals hold promise for innovative applications in magnetic hyperthermia.