VOLUME MAGNETOSTRICTION AND PRESSURE-DEPENDENCE OF THE CURIE-POINT AND SPONTANEOUS MAGNETIZATION OF WEAKLY FERROMAGNETIC Y(CO1-XALX)2

The pressure dependence of the Curie point of weakly ferromagnetic Y(Co1-xAlx)2 alloys for x approximately 0.15 has been measured at pressures up to 8 kbar. The pressure dependence of the spontaneous magnetization per unit mass at 0 K ( sigma 0) has been deduced for the same alloys from measurements of the forced volume magnetostriction in fields up to 12 T. It was found that ( delta ln T c/ delta ln V)=( delta ln sigma 0/ delta P)=120+or-17, one of the largest values known for a ferromagnetic material. The critical pressure for the collapse of ferromagnetism is approximately 9+or-1 kbar for 0.14<x<0.18, while the chemical pressure exerted by the Al in Y(Co 0.85Al0.15)2 is approximately -40 kbar, so weak ferromagnetism would not be possible in this Y-Co-Al system if the material was clamped to the volume of YCo2.