Effect of Cu substitution on structural and hard magnetic properties of rapidly solidified Zr18Co82-xCux melt spun ribbons

The necessity to have rare earth free permanent magnets has driven the research efforts world over to explore the rare earth free compositions to make permanent magnets. The composition of Zr18Co82-xCux (x = 0-3) was chosen, melt spun followed by a detailed investigation on structural and magnetic properties. The melt spun ribbons obtained from these nominal compositions contained rhombohedral (R) Zr2Co11, orthorhombic (O) Zr2Co11 and fcc Co phases. The substitution of near atomic radius Cu for Co results in increase of O-Zr2Co11 phase. As a result, for an increase of Cu content from x = 0 to 3, the saturation magnetization (Ms) increases from 56 to 101emu/g, while the coercivity (Hc) decreases monotonously from 2.2 to 1.5 kOe. The easy magnetization direction lies along the plane of the ribbon. There is a significant change in the solidification morphology of the ribbons as a function of Cu content. It changes from dendritic to equiaxed and again to dendritic with increase in Cu addition.