Title :
Nanocomposite R2Fe14B/α-Fe permanent magnets
Author :
Hadjipanayis, G.C. ; Withanawasam, L. ; Krause, R.F.
Author_Institution :
Dept. of Phys. & Astron., Delaware Univ., Newark, DE, USA
fDate :
11/1/1995 12:00:00 AM
Abstract :
We have studied the crystallization, crystal structure, structure morphology, and magnetic properties of R6Fe87Nb 1B6 with R=Nd, Pr, Dy, Tb and Nd3.5Fe 91Nb2B3.5 melt-spun ribbons with a microstructure consisting of a mixture of exchange-coupled magnetically hard (R2Fe14B1) and soft (α-Fe) phases. The as-spun ribbons of R-rich composition crystallize in two steps; at first the Y3Fe62B14-type+α-Fe phases are formed for R=Nd, Pr, and Dy and subsequently they transform to 2:14:1 and α-Fe upon heating above 700°C. The intermediate phase in the case of Tb6Fe87Nb1B6 is of the TbCu7-type. Very high remanences up to 145 emu/g with reduced remanences, Mr/Ms, up to 0.8 were observed. The coercivity of the samples was found to vary with the R element and the content of the hard phase. The highest room temperature coercivity of 4.5 kOe was obtained in a Nd4Tb2Fe 36Nb2B6 sample. Electron microscopy reveals a grain size of 30-50 nm, which is much larger than the size (10 nm) predicted for optimum coupling
Keywords :
boron alloys; coercive force; composite materials; crystal structure; crystallisation; electron microscopy; ferromagnetic materials; grain size; iron; iron alloys; melt spinning; nanostructured materials; permanent magnets; phase equilibrium; rare earth alloys; remanence; soft magnetic materials; 30 to 50 nm; 700 C; Dy6Fe87NbB6; Nd3.5Fe91Nb2B3.5; Nd3.5Fe91Nb2B3.5 melt-spun ribbons; Nd4Tb2Fe36Nb2B6 ; Nd6Fe87NbB6; Pr6Fe87NbB6; R6Fe87Nb1B6; Tb6Fe87Nb1B6; Tb6Fe87NbB6; Y3Fe62B14-type+α-Fe phases; as-spun ribbons; coercivity; crystal structure; crystallization; electron microscopy; exchange-coupled magnetically hard R2Fe14B 1 phases; grain size; high remanence; intermediate phase; magnetic properties; microstructure; nanocomposite R2Fe14B/α-Fe permanent magnets; room temperature; soft α-Fe phases; structure morphology; Coercive force; Crystal microstructure; Crystallization; Heating; Iron; Magnetic properties; Morphology; Neodymium; Niobium; Temperature;
Journal_Title :
Magnetics, IEEE Transactions on
