On the appearance of ferromagnetism in Y(Co1−xAlx)2 alloys

The appearance of ferromagnetism in Y(Co_1?xAl_x)₂ is discussed in terms of a d band model. The approximate d bands for YCo₂ and Y(Co_1?x)₂ are calculated and the decrease in the electronic energy due to magnetization of the spin of estimated. The energy decrease is the largest in YCo₂, and it gradually decreases as the Al content increases, if the lattice constant is fixed, while this energy decrease increases if the lattice constant increases with increasing Al content. These results of calculations give a good account of the appearance of ferromagnetism in Y(Co_1?xAl_x)₂ around x = 0.15. The ferromagnetism in Sc(CO_1?xAl_x)₂ is also discussed, leading to the appearance of ferromagnetism between x = 0.15 and 0.30.