Magnetic properties of single and multi‐domain magnetite under pressures from 0 to 6 GPa

Abstract

Using novel experimental methods, we measured the acquisition of isothermal remanent magnetization, direct field demagnetization, and alternating field demagnetization of multi‐domain (MD) and single domain (SD) magnetite under hydrostatic pressures to 6 GPa. We find that the saturation remanence of MD magnetite increases 2.8 times over initial, non‐compressed values by 6 GPa, while its remanent coercivity remains relatively constant. For SD magnetite, remanent coercivity and saturation remanence vary little from 0 to 1 GPa, increase markedly from 1 to 3 GPa, then plateau above 3 GPa. These new findings suggest that by 3 GPa, SD magnetite either undergoes a magnetic phase transition, or that it reaches an optimal magnetic state where magnetostriction and/or magnetocrystalline energy constants attain some threshold state without reorganization of the pre‐existing magnetic lattices. Similar behavior is not observed in MD magnetite, likely due to domain wall effects.