Magnetism of interface regions studied by electron holography

This overview article reports on the electron holography studies about the magnetism of interface regions in metallic alloys. Recent progress of electron holography enabled pin-point analysis of the magnetic flux density from nanometer-scale interface regions; e.g., antiphase boundaries (APBs) produced in ordered alloys, and the amorphous grain-boundary phase in sintered magnets. The observations have demonstrated magnetism that is amplified by structural disorder within APBs produced in Fe₇₀Al₃₀, which appears in contrast to the traditional understating. With respect to the ultrathin grain-boundary phase in a Nd-Fe-B magnet, the electron holography study determined the magnetic flux density at 1.0 T (± 0.1 T). The result provided useful information for deeper understanding of the coercivity mechanism in the Nd-Fe-B sintered magnet.