Effect of Mo concentration on the phase composition and magnetic properties of Nd8(Fe,Mo)86B6 nanocomposite magnets

Abstract

The phase composition and magnetic properties of Nd8Fe86−xMoxB6 (x=0, 1, 2, and 3) nanocomposite magnets prepared by melt spinning have been investigated by x-ray powder diffraction, transmission electron microscopy, thermomagnetic analysis, and vibrating sample magnetometer measurements. The optimal ribbons were found to be mainly composed of the α-Fe phase and the Nd2Fe14B phase. The average crystalline size of α-Fe is 14–18 nm. In the optimally quenched samples, the α-Fe phase content decreases with increasing Mo content; at the same time, an increase of coercivity and a decrease of energy products are observed. The hysteresis loops of the optimal ribbons show a single-phase hard magnetic behavior. The reduced remanence ratio is always above 0.66. The remanence enhancement is due to the exchange coupling between the soft and hard magnetic phases in these ribbons. The Curie temperature of the Nd2Fe14B phase in the samples decreases with increasing Mo content. The optimal hard magnetic properties of remanence, coercivity, reduced remanence, and maximum energy product are 120 emu/g, 4.5 kOe, and 0.75 and 135 kJ/m3, respectively, for Nd8Fe86B6.