Effect of magnetocrystalline anisotropy on the magnetic properties of Fe-rich R–Fe–B nanocomposite magnets

Abstract

Nanocomposite ribbons consisting of hard-magnetic R2Fe14B (R=rare-earth) and soft-magnetic Fe3B phases were produced by melt spinning and subsequent heat treatment. Alloys of composition Nd4−xSmxFe77.5B18.5, with x=0.0, 0.1, 0.2, 0.3, 0.4, and 0.5 all showing strong remanence enhancement, were selected to investigate the effect of the magnetocrystalline anisotropy of the R2Fe14B-type phase on the exchange coupling with the soft-magnetic phase in the nanocomposite magnets. An enhancement of exchange coupling due to anisotropy reduction was found, as expected on the basis of the model of Kneller and Hawig. A maximum of the energy product (BH)max was achieved for x=0.2 after annealing at 700 °C. The thermomagnetic behavior also changes upon substitution of Sm for Nd.

Beneficial effect of the substitution of Co for Fe on the magnetic properties of melt-spun Pr2Fe14C/α-Fe-type nanocomposite magnets

“…If the intergranular exchange coupling is strong enough, the magnetic properties of nanocomposites can be enhanced by optimizing the intrinsic properties of the magnetic phases such as saturation magnetization and anisotropy field [4,5]. Many experimental results show that a moderate substitution of Co for Fe can increase the saturation magnetization (at room temperature) of magnetically hard and soft phases, and so significantly improve the magnetic properties of (Nd, Pr) 2 Fe 14 B/␣-Fe nanocomposites [6][7][8][9].…”

Magnetism of rapidly quenched rhombohedral Zr2Co11-based nanocomposites

“…This reflects that the exchange correlation length (ECL) among magnetic phases is almost unchanged down to 100 K. Generally, ECL corresponds to the domain wall width of the hard magnetic phase, 2π(A/K) 1/2 , where A and K are the exchange constant and the magnetocrystalline anisotropy parameter of the hard magnetic phase, respectively. [10] Therefore, it is concluded that K slightly changes with the decrease in temperature. K can be estimated by fitting the high-field magnetization measurements to the following expression: [11] M…”

Remanent enhancement of nanocomposite (Nd, Sm)2Fe14B/α-Fe magnets

“…It is also interesting to calculate the area ratio for a more clear assessment of the exchange-coupling enhancement, which is defined as the ratio of the area below the demagnetization curve in the second quadrant to the product of coercivity and remanence [10]. As shown in Fig.…”

“…Zhao et al systematically investigated (Nd, Sm) 2 Fe 14 B/ Fe 3 B nanocomposite magnets by melt spinning [10]. An enhancement of the exchange coupling length was found to relate with the reduction of the magnetocrystalline anisotropy of the magnetically hard phase by Sm substitution for Nd.…”