Evidence for the presence of a soft magnetic layer on the surface of die upset melt quenched Nd-Fe-B

Magnetic properties on the surface of the anisotropic melt quenched Nd-Fe-B material were studied and compared with the properties of the material in bulk. The coercive field is 10.3 kOe on the surface and 14.9 kOe in the bulk. The reversible susceptibility is much higher and the irreversible susceptibility is much lower on the surface than in the bulk. Open recoil loops on the surface are observed. The lower coercive field and higher reversible susceptibility are due to the presence of a soft magnetic phase on the surface. Open recoil loops are due to exchange coupling between the soft magnetic phase on the surface and the hard magnetic phase in the bulk material.