Crystalline evolution and large coercivity in Dy-doped (Nd,Dy)₂Fe₁₄B/α-Fe nanocomposite magnets

Abstract

Nanocomposite hard magnetic materials (Nd,Dy)4.5Fe77.5B18 (No. 1) and (Nd,Dy)4.5Fe76B18Nb1.2Cu0.3 (No. 2) have been prepared by crystallizing amorphous ribbons, fabricated by single roll melt-spinning. The evolution of a multiphase structure was monitored by an x-ray diffractometer and by thermomagnetic measurement. We observed that, at annealing temperatures below 670 °C, there is crystallization of soft phase Fe3B and a small amount of hard phase Nd2Fe14B. At annealing temperatures above 670 °C, crystallization of α-Fe and probably Dy2Fe14B phases with large magnetocrystalline anisotropy led to a drastic enhancement in the hard magnetic properties of the materials. The maximum value of HC is found to be 4.2 kOe for sample No. 1. For sample No. 2, with co-doping of Nb and Cu, nanostructure refinement yields a strong enhancement in exchange coupling between the component phases. Thereby, we obtained high reduced-remanence of 0.78, high remanence of 1.15 and a high (BH)max value up to 16.2 MGOe.

The microstructure, high performance magnetic hardness and magnetic after-effect of an α- FeCo/Pr2Fe14B nanocomposite magnet with low Pr concentration

“…In previous studies [9,10], we have presented our achievements on high performance nanocomposite magnets with low rare-earth content. Moreover, the preparation is the simple rapid-quenched technique, which easily produces the materials on a large scale.…”

The Effects of the Addition of Dy, Nb, and Ga on Microstructure and Magnetic Properties of Nd2Fe14B/α-Fe Nanocomposite Permanent Magnetic Alloys

“…The exchange coupling between soft and hard magnetic grains with nanometer size enhances the remanence, however, it decreases the coercivity (Schrefl et al, 1994 a ). The substitution of Dy for Nd is an effective method to improve the coercivity in nanocomposite alloys by increasing the anisotropy field of the hard magnetic Nd 2 Fe 14 B phase (Chen et al, 2004; The et al, 2007). Unfortunately, Dy has been considered as an unfavorable element because of its increased price and uncertain availability.…”

Influence of quenching rate and composition on optimal annealing temperature of Nd–Fe–B based nanocrystalline hard magnetic alloys

“…[3][4][5][6] To enhance the coercivity, Nd is often substituted partly by Dy, Tb or Pr because these additional elements have larger magnetocrystalline anisotropy than that of Nd. [7][8][9][10][11] To enhance Curie temperature of the material, the addition of Co is the most suitable way because Co can substitute for Fe in Nd 2 (Fe,Co) 14 B phase. [12][13][14] Other additional elements such as Mo, Ta, Ti, V, Zr, C, etc.…”