Ferromagnetic resonance heating of Fe and Fe₃O₄by 5.8 GHz microwave irradiation

Abstract

Compressed Fe3O4 powder and Fe sheet were pre-heated to various temperatures higher than 300 °C in a microwave magnetic field (hrf). Then an external static magnetic field (Hext) was imposed perpendicularly to hrf and the temperature increased (ΔT: temperature difference from the pre-heated temperature, ΔTmax: ∼200 °C (Fe), ∼50 °C(Fe3O4)). It had a peak at almost the same Hext during ascent and descent of Hext because of ferromagnetic resonance (FMR). In fact, ΔT became smaller as the preheating temperature was raised to approach the Curie temperature, and Hext corresponding to the temperature peak shifted higher. This report provides FMR heating data under various conditions with quantitative discussion and proposes application of a new heat treatment to materials.