Analyzing coercivity mechanism is one of the key problems to understand magnetic behavior and to improve the magnetic properties of ferromagnetic materials including permanent magnets.
Up to now, many studies have been done to analyze the coercivity mechanisms of different kinds of permanent magnets, especially rare earth nanocrystalline permanent magnets based on Nd-Fe-B or Sm-Co alloys.
The coercivity mechanism of nanocrystalline magnets also depends on microstructures, especially on grain boundary phase. A study on coercivity of Nd-Fe-B sintered magnets showed that existence of amorphous Nd-rich grain boundary between Nd2Fe14B grains strengthens domain wall pinning so that coercivity is enhanced. And a study on the magnetic properties of high performance Dy-doped Nd-Fe-B sintered magnet concluded that the Dy-rich shell increases the nucleation field from the grain boundary and the Nd-rich layers weaken the inter-granular exchange coupling to enhance coercivity.
Kim Kyong Gi, a researcher at the Faculty of Physical Engineering, evaluated and analysed the relationship between coercivity and α-Fe layer thickness in an exchange coupled Nd2Fe14B/α-Fe nanocomposite multilayer system by comparing the results of previous experimental and micromagnetic studies.
The results showed that the coercivity decreases with increasing α-Fe layer thickness, which is coincident with the results of prior micromagnetic and experimental studies.
For further information, please refer to his paper “An analytic study on coercivity mechanism of exchange coupled Nd2Fe14B/α-Fe nanocomposite magnets” in “Journal of Magnetism and Magnetic Materials” (SCI).
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