Magnetism of rapidly quenched rhombohedral Zr₂Co₁₁-based nanocomposites

Abstract

The effect of quench rate and Zr content on nanostructure and magnetic properties of melt-spun ZrxCo100−x (x = 16-21) is investigated. High quench rate favors the formation of rhombohedral Zr2Co11, which is the hard phase. The coercivity increases with an increase in quench rate. Zr addition in limited amounts decreases the grain size of magnetic phases, which may promote the effective exchange coupling of soft magnetic phases. Therefore, coercivity and maximum energy product of Zr2Co11-based materials are significantly enhanced. The best magnetic properties, iHc = 3.0 kOe and (BH)max = 4.6 MG Oe, which are the highest reported values among Co-Zr binary alloys, are achieved for x = 18. The temperature coefficients of coercivity and remanence between 100 and 380 K are −0.05% K −1 , comparable to those of alnico magnet.

Novel Nanostructured Rare‐Earth‐Free Magnetic Materials with High Energy Products

“…Bulk Zr2Co11 alloys crystallize in rhombohedral or orthorhombic structures, [7,8] but the XRD pattern of Zr2Co11 nanoparticles (red curve) is in good agreement with that of the rhombohedral bulk structure (blue curve) as shown in figure 2a. Note that the Co-Zr bulk phase diagram, shown in figure 2b, indicates the formation of Zr2Co11 equilibrium phase only at a single composition (solid red vertical line).…”

“…However, the range of alternative compounds with appreciable K1 and high Tc is limited, and the situation is often aggravated by their metastable nature and by the requirement of high-formation temperatures. [5][6][7][8][9][10][11][12] For example, two suitable candidates are Zr2Co11 and HfCo7, both crystallizing in noncubic structures, as necessary for high K1. However, the poor control over phase purity in traditionally prepared bulk alloys has an adverse effect on permanent magnetic properties.…”

“…However, the poor control over phase purity in traditionally prepared bulk alloys has an adverse effect on permanent magnetic properties. [7,8,11,12] The future development requires high-performance magnetic materials for applications ranging from home appliances to sophisticated microelectronics and environment-friendly technologies, such as hybrid vehicles and wind turbines. [1][2][3][4] Synthesis of magnetic materials in the form of nanoparticles smaller than 10 nm has emerged as an alternative method to stabilize traditional or new crystal structures.…”

Phase composition and nanostructure of Zr2Co11-based alloys

“…[1][2][3] Depending on the preparation process, the crystal structure of Zr 2 Co 11 may be rhombohedral or orthorhombic. [4][5][6] Among these phases, rhombohedral Zr 2 Co 11 has been demonstrated to be the hard magnetic phase, 7 and a high quenching rate favors the formation of the hard magnetic phase. 8 Recently, an impressive energy product comparable to that of sintered SmCo 5 was obtained for the easy-axis aligned Zr 2 Co 11 -based nanocomposites produced by a single step cluster-deposition method.…”

Effect of annealing on nanostructure and magnetic properties of Zr2Co11 material

“…It was reported that a high quench rate is required in order to obtain good magnetic properties because it increases the volume fraction of the hard magnetic phase. [7] B addition was found to refine the grain size and increase the coercivity. [8] Ti addition suppressed the formation of Zr2Co11 dendrites upon solidification, refined the structure, and enhanced the coercivity.…”