Magnetic properties of Co–Al–Ni melt-spun ribbon

Abstract

Co–Al–Ni alloys were produced by melt-spinning followed by heat treatment. X-ray and thermomagnetic studies revealed that the rapidly solidified melt-spun ribbons consisted of a nonequilibrium bcc-(Co,Ni)Al-type structure. The Curie temperature was closely dependent on the Ni content of the Co–Al–Ni alloy. Although the Co–Al–Ni melt-spun ribbons had low coercivity, annealing of the ribbons at 823K for 1h resulted in an increase in the coercivity. The coercivity of the annealed Co–Ni–Al melt-spun ribbon was also dependent on the Ni content. The Curie temperature of the β-(Co,Ni)Al phase in the annealed Co–Ni–Al melt-spun ribbon decreased as its Ni content increased. Annealed Co30Al30Ni40 melt-spun ribbon with hcp-(Co,Ni) and β-(Co,Ni)Al phases exhibited the highest coercivity of 2.0kOe. The origin of the high coercivity in the annealed Co–Al–Ni melt-spun ribbon was found to be the formation of the hcp-(Co,Ni) phase. It was found that annealing at 1173K for 1h resulted in the formation of the fcc-(Co,Ni) and β-(Co,Ni)Al phases and led to a drastic decrease in the coercivity.