Shock induced Nd2Fe14B magnetic transition based on molecular field theory analysis

Abstract

According to the shock wave experiment on the Nd2Fe14B ferromagnet, the relationship between pressure and temperature on the shock front is calculated in a pressure range from 3.3 GPa to 7.2 GPa. In order to analyze the magnetic transition mechanism of Nd2Fe14B under different temperatures and applied pressures, the equivalent pressure field is introduced to improve the two-sublattice model based on the molecular field theory. The pressure dependence of magnetostriction coefficient, susceptibility, magnetization, and Curie temperature of Nd2Fe14B are calculated. The criteria of the ferromagnetic-paramagnetic phase transition occurring in Nd2Fe14B at different temperatures and pressures are obtained. The results indicate that the Curie temperature of Nd2Fe14B decreases as pressure increases. The Curie temperature reduces from 584 K at 0 GPa to 298 K at 1.142 GPa. With the increasing of pressure, the magnetization of Nd2Fe14B declines. The critical demagnetization pressure of Nd2Fe14B also decreases with the increasing of temperature. In a pressure region from 3.3 GPa to 7.2 GPa, there appears the pressure induced ferromagnetic-paramagnetic phase transition of Nd2Fe14B.