Magnetic microstructure of a textured Nd–Fe–B sintered magnet characterized by small-angle neutron scattering

• The characterization of textured Nd–Fe–B magnets by small-angle neutron scattering is addressed.
• Long-range spin-misalignment fluctuations exist up to the micron range.
• Polarized neutrons provide evidence for the presence of coupled nuclear-magnetic nanometer-scale fluctuations.
• SANS is a powerful technique for characterizing the magnetic microstructure of Nd–Fe–B magnets on a mesoscopic length scale (1 ∼ 1000 nm).

We report the results of a small-angle neutron scattering (SANS) study on the magnetic microstructure of a textured Nd–Fe–B-based sintered permanent magnet. By combining unpolarized and polarized SANS (SANSPOL), we demonstrate that a number of important conclusions regarding the microscopic spin structure can be made. Specifically, the applied-field dependence of the unpolarized neutron data is in agreement with the existence of long-range spin-misalignment fluctuations, i.e., deviations of the magnetization from the mean direction on a real-space length-scale up to the micron range. In addition, measurements with polarized neutrons provide evidence for the presence of coupled nanometer-scale fluctuations in the nuclear and longitudinal magnetic scattering-length density.