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The mechanism of rapid and selective heating of magnetic metal oxides underthe magnetic field of microwaves which continues beyond the Curie temperature $T_{c} $ is identified by using the Heisenberg model. Monte Carlo calculationsbased on the energy principle show that such heating is caused by non-resonantresponse of electron spins in the unfilled 3d shell to the wave magnetic field.Small spin reorientation thus generated leads to a large internal energy changethrough the exchange interactions between spins, which becomes maximal around $T_{c} $ for magnetite $ {\rm Fe}_{3}{\rm O}_{4} $. The dissipative spindynamics simulation yields the imaginary part of the magnetic susceptibility,which becomes largest around $ T_{c} $ and for the microwave frequency around 2GHz. Hematite $ {\rm Fe}_{2}{\rm O}_{3} $ with weak spontaneous magnetizationresponds much less to microwaves as observed in experiments. The heating oftitanium oxide by microwave magnetic field only when oxygen defects are presentis also explained by our theory in terms of the absence of spontaneousmagnetization.

Selective Heating Mechanism of Magnetic Metal Oxides by Alternating Magnetic Field in Microwave Sintering Process