Unmasking the interior magnetic domain structure and evolution in Nd-Fe-B sintered magnets through high-field magnetic imaging of the fractured surface

In Nd-Fe-B sintered magnets, observations of how reversed magnetic domains propagate throughout the entire hysteresis loop have been restricted to polished surfaces or transmittable thin films. However, the mechanical processing of the surface introduces defects that nucleate additional reversed magnetic domains which mask the underlying domain pattern. To unmask the interior magnetic domain structure that represents the bulk, soft x-ray absorption microscopy is utilized in this paper to track the reversal of individual grains in the polished and fractured surfaces. Significant variation in the reversal behavior is observed and intergranular correlations are identified. Videos of the magnetic domain propagation accompany this paper.