TY - JOUR
T1 - Selective heating mechanism of magnetic metal oxides by a microwave magnetic field
AU - Tanaka, Motohiko
AU - Kono, Hirohiko
AU - Maruyama, Koji
PY - 2009/3/3
Y1 - 2009/3/3
N2 - The mechanism of rapid and selective heating of magnetic metal oxides under the magnetic field of microwaves which continues beyond the Curie temperature Tc is identified by using the Heisenberg model. Monte Carlo calculations based on the energy principle show that such heating is caused by nonresonant response of electron spins in the unfilled 3d shell to the wave magnetic field. Small spin reorientation thus generated leads to a large internal energy change through the exchange interactions between spins, which becomes maximal around Tc for magnetite Fe3 O4. The dissipative spin dynamics simulation yields the imaginary part of the magnetic susceptibility, which becomes largest around Tc and for the microwave frequency around 2 GHz. Hematite Fe2 O3 with weak spontaneous magnetization responds much less to microwaves as observed in experiments. The heating of titanium oxide by microwave magnetic field only when oxygen defects are present is also explained by our theory in terms of the appearance of spontaneous magnetization.
AB - The mechanism of rapid and selective heating of magnetic metal oxides under the magnetic field of microwaves which continues beyond the Curie temperature Tc is identified by using the Heisenberg model. Monte Carlo calculations based on the energy principle show that such heating is caused by nonresonant response of electron spins in the unfilled 3d shell to the wave magnetic field. Small spin reorientation thus generated leads to a large internal energy change through the exchange interactions between spins, which becomes maximal around Tc for magnetite Fe3 O4. The dissipative spin dynamics simulation yields the imaginary part of the magnetic susceptibility, which becomes largest around Tc and for the microwave frequency around 2 GHz. Hematite Fe2 O3 with weak spontaneous magnetization responds much less to microwaves as observed in experiments. The heating of titanium oxide by microwave magnetic field only when oxygen defects are present is also explained by our theory in terms of the appearance of spontaneous magnetization.
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U2 - 10.1103/PhysRevB.79.104420
DO - 10.1103/PhysRevB.79.104420
M3 - Article
AN - SCOPUS:64849110259
VL - 79
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
SN - 0163-1829
IS - 10
M1 - 104420
ER -