Temperature dependence of coercivity in melt-spun and die upset neodymium-iron-boron

Journal Article · Tue May 01 04:00:00 EDT 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.344775· OSTI ID:6837248

Pinkerton, F E; Fuerst, C D ^[1]

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1. Physics Department, General Motors Research Laboratories, Warren, Michigan 48090-9055 (USA)

We compare the temperature dependence of the intrinsic coercivity {ital H}{sub {ital ci}} between 5 and 600 K in rapidly quenched Nd-Fe-B ribbons and a die upset Nd-Fe-B magnet. At room temperature, ribbons have higher coercivity than the die upset magnet, but have a smaller technical temperature coefficient of coercivity {beta} between 25 and 125 {degree}C: {ital H}{sub {ital ci}}=15.1 kOe and {beta}={minus}0.38%/{degree}C for the ribbons, while {ital H}{sub {ital ci}}=10.4 kOe and {beta}={minus}0.64%/{degree}C for the die upset magnet. Because the die upset magnet has a stronger temperature dependence, the {ital H}{sub {ital ci}}({ital T}) curves converge at low temperature. The ribbons can be phenomenologically modeled using {ital H}{sub {ital ci}}({ital T})={ital cH}{sub {ital A}}({ital T}){minus}{ital N}{sub eff}4{pi}{ital M}{sub {ital s}}({ital T}), the two terms representing the strength of domain wall pinning at grain boundaries and the effective local demagnetizing field, respectively. The model parameters {ital c}=0.25 and {ital N}{sub eff}=0.26 are significantly smaller than the corresponding values obtained in sintered Nd-Fe-B magnets. This model is less successful in describing {ital H}{sub {ital ci}}({ital T}) for the die upset magnet. Their qualitatively different behaviors indicate that different mechanisms of domain wall pinning are responsible for coercivity in ribbons and die upset magnets.

• OSTI ID: 6837248
• Journal Information: Journal of Applied Physics; (USA), Journal Name: Journal of Applied Physics; (USA) Vol. 67:9; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
BORIDES
BORON COMPOUNDS
COERCIVE FORCE
CRYSTAL STRUCTURE
GRAIN BOUNDARIES
HIGH TEMPERATURE
IRON BORIDES
IRON COMPOUNDS
LOW TEMPERATURE
MAGNETIC PROPERTIES
MAGNETS
MATHEMATICAL MODELS
MEDIUM TEMPERATURE
MICROSTRUCTURE
NEODYMIUM BORIDES
NEODYMIUM COMPOUNDS
PERMANENT MAGNETS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE