Hydrostatic pressure effect on magnetic hysteresis parameters of pseudo‐single‐domain magnetite

Abstract

AbstractThis paper reports the first in situ magnetic hysteresis measurements of pseudo‐single‐domain (PSD) magnetite under high pressure up to 1 GPa. The magnetic hysteresis measurements of stoichiometric PSD magnetite samples under hydrostatic pressure were carried out using a piston‐cylinder high‐pressure cell, and the pressure dependence of the hysteresis parameters of PSD magnetite was calculated from the hysteresis curves. It was found that coercivity (Bc) increases with increasing pressure as a quadratic function up to 1 GPa by ∼90%, which is different from the pressure dependences of Bc of multidomain and single‐domain magnetites. Coercivity of remanence also increases as a quadratic function, and saturation remanence (Mrs) increases with pressure up to 0.5 GPa by ∼20% until reaching saturation. In contrast, saturation magnetization is constant up to 1 GPa. The approximate demagnetizing factor calculated from the ratio Bc/Mrs increases with increasing pressure, suggesting that the number of lamellar domains increases with increasing pressure. The number of lamellar domains and domain wall width are theoretically estimated to increase under high pressure due to the changes in magnetostriction, elastic, and magnetocrystalline anisotropy constants, and these changes in magnetic domain structure should relate to the changes in the magnetic properties of PSD magnetite.