Study of the magnetic interaction in nanocrystalline Pr–Fe–Co–Nb–B permanent magnets

The magnetic properties of an isotropic, epoxy resin bonded magnets made from Pr–Fe–Co–Nb–B powder were investigated. The magnetization reversal process and magnetic parameters were examined by measurements of the initial magnetization curve, major and minor hysteresis loops and sets of recoil curves. From the initial magnetization curve and the field dependencies of the reversible and irreversible magnetization components derived from the recoil loops it was found that the magnetization reversal process is the combination of the nucleation of reversed domains and pinning of domain walls at the grain boundaries and the reversible rotation of magnetization vector in single domain grains. The interactions between grains were studied by means of δM plots. The nonlinear behavior of δM curve approve that the short range intergrain exchange coupling interactions are dominant in a field up to the sample coercivity.The interaction domains and fine magnetic structure were revealed as the evidence of exchange coupling between soft α-Fe and hard magnetic Nd2Fe14B grains.

▸ Coercivity of the Pr–Fe–Co–Nb–B magnet is determined by the pinning of domain walls at the grain boundaries. ▸ Rotation of magnetization vector and domain walls bowing also give the contribution to the initial and demagnetization process. ▸ δM behavior shows that the dominant interaction is the short range exchange one among soft magnetic α-Fe and hard magnetic Pr2Fe14B grains.