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Electrical Resistivity and Demagnetization Characteristics of Salt-added Nd-Fe-B-type Magnet
Journal of Magnetics, Volume 24, Number 3, 30 Sep 2019, Pages 477-484
Abstract
Nd-Fe-B-type die-upset magnet with high electrical resistivity was fabricated by hot-deforming the mixture of melt-spun Nd-Fe-B-type flakes (MQU-F: Nd13.6Fe73.6Co6.6Ga0.6B5.6) and Dy-containing salts: eutectic (DyF3–LiF) salt mixture and DyF3 single salt. Profound electrical resistivity enhancement was feasible in the Nd-Fe-B-type die-upset magnet by adding Dy-containing salts. More profound electrical resistivity enhancement was achieved in the magnet added with dielectric eutectic (DyF3–LiF) salt mixture with respect to the magnet added with single DyF3 salt. This was attributed to better electrical insulation between the flakes by forming more continuous coverage of the flake interface with the easily melted dielectric salt. Coercivity of the die-upset magnet was also profoundly enhanced by optimal addition of Dy-containing salts, and this was attributed to substitution of some Nd in the Nd2Fe14B-type grains near flake surface by Dy atoms from the added salt. Kerr microscopy revealed that for both the magnets with or without salt addition, formation of reverse domain initiated mostly inside the flake. Reversed domain started to form at higher reverse field for the magnet added with Dy-containing salt than for the magnet without salt addition. Practical demagnetization occurred largely by formation of new reverse domains at random places rather than enlargement of previously formed reverse domain for both the magnets with or without salt addition.
Keywords: Nd-Fe-B magnet; die-upset magnet; electrical resistivity; demagnetization process; Kerr microscopy
DOI: https://doi.org/10.4283/JMAG.2019.24.3.477
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