Structure and magnetic properties of Ga doped Nd13.65Fe74.15B5.6Co6.6 ribbons

Abstract

The addition of low melting point Ga changed the crystallization process and microstructure of the Nd13.65Fe74.15B5.6Co6.6 ribbons. The Ga addition improves the glass-forming ability of the ribbons, and the ribbons melt-spun at 25 m/s are composed of Nd2(Fe, M)14B phases with different Nd contents and Nd-rich amorphous grain-boundary phase. Nd2(Fe, M)14B grains have a gradient size of 50–300 nm, also, the large-sized grains are slightly rich in Fe-Co, and the small-sized ones are rich in Nd. Compared to the Ga-free alloy, 0.6 at% Ga addition narrows the grain boundary width to 5.5 ± 4.5 nm, promotes the enrichment of Ga atoms at grain boundaries and form Nd(Fe, Co)1.62Ga0.04 composition, improved the intergranular exchange coupling and magnetic properties of the ribbons most significantly, increasing the coercivity and remanence by 52.6% and 36.6% respectively. Besides, the microstructure models changed by Ga addition are established, and the corresponding solidification processes and magnetic mechanisms are discussed.