Influence of defect thickness on the angular dependence of coercivity in rare-earth permanent magnets

The coercive field and angular dependence of the coercive field of single-grain Nd2Fe14B permanent magnets are computed using finite element micromagnetics. It is shown that the thickness of surface defects plays a critical role in determining the reversal process. For small defect thicknesses rever...

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Bibliographic Details
Published in:Applied physics letters 2014-05, Vol.104 (18)
Main Authors: Bance, S., Oezelt, H., Schrefl, T., Ciuta, G., Dempsey, N. M., Givord, D., Winklhofer, M., Hrkac, G., Zimanyi, G., Gutfleisch, O., Woodcock, T. G., Shoji, T., Yano, M., Kato, A., Manabe, A.
Format: Article
Language:English
Subjects:
Applied physics
Coercivity
Computation
Crystal defects
Defects
Dependence
Domain walls
Finite element method
Grain boundaries
Infiltration
Nucleation
Permanent magnets
Physics
Rare earth elements
Surface defects
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Summary:The coercive field and angular dependence of the coercive field of single-grain Nd2Fe14B permanent magnets are computed using finite element micromagnetics. It is shown that the thickness of surface defects plays a critical role in determining the reversal process. For small defect thicknesses reversal is heavily driven by nucleation, whereas with increasing defect thickness domain wall de-pinning becomes more important. This change results in an observable shift between two well-known behavioral models. A similar trend is observed in experimental measurements of bulk samples, where an Nd-Cu infiltration process has been used to enhance coercivity by modifying the grain boundaries. When account is taken of the imperfect grain alignment of real magnets, the single-grain computed results appears to closely match experimental behaviour.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4876451