Magnetic structure and microstructure of die-upset hard magnets RE{sub 13.75}Fe{sub 80.25}B{sub 6} (RE=Nd, Pr): A possible origin of high coercivity
- Department of Applied Science, Brookhaven National Laboratory, Upton, New York 11973 (United States)
{ital In situ} transmission electron microscopy magnetizing experiments combined with Lorentz magnetic microscopy in Fresnel{endash}Foucault modes were used to characterize the magnetic structure of die-upset, high energy-product hard magnets Nd{sub 13.75}Fe{sub 80.25}B{sub 6} and Pr{sub 13.75}Fe{sub 80.25}B{sub 6}. Experimental observations indicate a well-aligned grain structure and quasiperiodic nonaligned {open_quotes}extended defect{close_quotes} layers transverse to press direction. The local remanence of the {open_quotes}defect{close_quotes} layers is far from saturation when the external field is removed. The layers are enriched with inclusions of approximate composition Nd{sub 7}Fe{sub 3}, generally with a polygonal shape, and are associated with the original ribbon interfaces. They may be responsible for a high coercivity mechanism, since the motion of reverse domains can be impeded by these layers, even when they are nucleated. Thus, a delayed nucleation of reversed domains seems to be a limiting factor for magnetization reversal and coercivity force. Both Lorentz magnetic imaging and high-resolution microscopy highlight the role of magnetocrystalline anisotropy for domain wall-grain boundary interactions and pinning. Local remanence was estimated directly from magnetic moment sensitive Foucault images. {copyright} {ital 1999 American Institute of Physics.}
- OSTI ID:
- 321464
- Journal Information:
- Journal of Applied Physics, Vol. 85, Issue 6; Other Information: PBD: Mar 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Ferromagnetic grain boundary signature in die-upset RE-Fe-B magnets
Ferromagnetic grain boundary signature in die-upset RE-Fe-B magnets