Nanocomposite R2Fe14B/Fe exchange coupled magnets

Abstract

We have studied the crystallization, crystal structure, microstructure and magnetic properties of R-Fe-B (R=Nd,Pr,Dy,Tb) based melt-spun ribbons consisting of a mixture of R2Fe14B and α-Fe phases. All the samples crystallize first to α-Fe and a metastable phase (Y3Fe62B14 for R=Nd,Pr,Dy and TbCu7 for R=Tb) before they finally transform to 2:14:1 and α-Fe. The highest values of coercivity and reduced remanence, 4.5 and 0.63 kOe, respectively, were obtained in a Nd3.85Tb2(Fe-Nb-B)94.15 sample. These properties are the result of a fine grain microstructure consisting of a mixture of α-Fe and 2:14:1 having an average grain size of 30 nm.

Nd-Fe-B Nanocomposite Thin Films: Influence of the Additions on the Structure and Hard Magnetic Properties

“…For Nd 2 Fe 14 B/α-Fe nanocomposite magnetic materials, the reduction of coercive field is attributed to the emergence of α-Fe after annealing. Because, the α-Fe and the metastable phases (such as Nd 3 Fe 62 B 14 ) usually precipitate from the amorphous precursor earlier than the Nd 2 Fe 14 B phase, and moreover, the α-Fe grains tend to grow coarse during the decomposition of metastable phase therefore leading to weakening of the intergrain exchange coupling, it is important to find a way to change the crystallization behavior of the amorphous phase and to restrain the excessive growth of the soft and hard magnetic grains (Withanawasam et al, 1994). Nanocomposite permanent magnets require nanostructured grain sizes, especially for the soft magnetic phase.…”

Effect of wheel speed on the crystallization behavior of as-quenched Nd-Fe-B alloys

“…Nanocomposite magnets consisting of a mixture of magnetically hard and soft phases show great potentials in the development of potential permanent magnet, [1][2][3][4][5][6] which has been increasingly demonstrated by both experimental studies [1][2][3] and micromagnetic modeling simulations. 4,5 Such nanocomposite microstructure is usually prepared by crystallization of amorphous alloys.…”

Time resolved in-situ synchrotron radiation diffraction investigation of grain-growth kinetics in magnetic nanocomposites

“…The exchange coupling between hard (NdDy) 2 (FeCo) 14 B and soft-magnetic α-(FeCo), Fe 3 B) constituent phases was shown to improve the hard magnetic properties of nanocomposite permanent magnets prepared by melt-spinning and subsequent annealing [4,5]. We report on a first attempt to synthesize exchange coupled hard magnets by high-energy mechanical alloying of elemental powders, followed by the in-situ formation of magnetic nanocomposites during continuous heating.…”

“…Increasing efforts were recently devoted to the further development of exchange coupled nanocomposite magnets [1][2][3][4][5]. The exchange coupling between hard (NdDy) 2 (FeCo) 14 B and soft-magnetic α-(FeCo), Fe 3 B) constituent phases was shown to improve the hard magnetic properties of nanocomposite permanent magnets prepared by melt-spinning and subsequent annealing [4,5].…”