Magnetic properties enhancement of α-Fe/Nd2Fe14B-type nanocomposites by Co substitution

Abstract

The phase evolution and magnetic properties of melt-spun Nd9.5(Fe1−xCox)85.5B5 (x=0, 0.05, 0.1, and 0.15) nanocomposites have been investigated. It was found that Co substitution for Fe, i.e., x=0.05–0.15, improves the Curie temperature (Tc), remanence (Br), and maximum energy product (BH)max of the materials obtained. Co substitution for Fe was found to promote grain coarsening, after thermal processing, in materials with a high Co concentration. Wohlfarth remanence analysis suggests that dilute-Co substitution for Fe increases the strength of the exchange coupling between the soft magnetic phases, α-(Fe, Co) and Nd2(Co, Fe)17, and the 2:14:1 phases. The increase in the saturation magnetization of α-(Fe, Co) and 2:14:1 phase, in conjunction with the enhanced exchanged coupling, presumably, result in an increased (BH)max of Nd9.5(Fe0.95Co0.05)85.5B5 and Nd9.5(Fe0.90Co0.10)85.5B5 samples. Once above a critical Co concentration, for the compositions studied, the strength of exchange coupling interactions between magnetically soft and hard phases does not seem to vary significantly with Co content. Moreover, both the irreversible loss of induction and reversible temperature coefficient of induction (conventionally referred to as α) of fully processed materials decrease with increasing Co concentration.