Nanocomposite R{sub 2}Fe{sub 14}B/{alpha}-Fe and Sm{sub 2}(Fe-Ga){sub 17}C{sub x}/{alpha}-Fe magnets
- Univ. of Delaware, Newark, DE (United States). Dept. of Physics and Astronomy
- Magnetics International, Inc., Burns Harbor, IN (United States)
The authors have studied the crystallization, crystal structure, microstructure, and magnetic properties of melt-spun ribbons of R{sub 6}(Fe-Nb){sub 88}B{sub 6} with R = Nd, Pr, Dy, Tb and Nd{sub 3.5}(Fe-Nb){sub 93}B{sub 3.5} consisting of a mixture of exchange-coupled magnetically hard R{sub 2}Fe{sub 14}B and soft {alpha}-Fe phases. The as-spun ribbons of R-rich composition crystallize in two steps; for LR-Nd, Pr, and Dy at first the Y{sub 3}Fe{sub 62}B{sub 14}-type + {alpha}-Fe phases and subsequently they transform to 2:14:1 and {alpha}-Fe upon heating above 700 C. The intermediate phase in the case of Tb{sub 6}(Fe-Nb){sub 88}B{sub 6} is of the TbCu{sub 7}-type. Very high remanences up to 145 emu/g with reduced remanences ranging from 0.6 to 0.7 were observed. The coercivity of the samples was found to vary with the R element and the hard phase content. The highest room temperature coercivity of 4.5 kOe was obtained in a Nd{sub 4}Tb{sub 2}(Fe-Nb){sub 88}B{sub 6} sample. The observed reversible demagnetization curves are characteristic of exchange-spring magnets. A two-phase microstructure was also obtained in Sm-Fe-Ga-C ribbons consisting of exchange-coupled 2:17 and {alpha}-Fe phases after annealing in the temperature range of 700--800 C. The highest coercive force (12.8 kOe) was obtained in samples annealed at 800 C. Annealing at 700 C led to infer grains with lower coercivities (5kOe) but higher remanences.
- OSTI ID:
- 131462
- Journal Information:
- Scripta Metallurgica et Materialia, Vol. 33, Issue 10-11; Other Information: PBD: 1 Dec 1995
- Country of Publication:
- United States
- Language:
- English
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