Itinerant-electron metamagnetism in Y(Co1-xNix)5

The magnetization processes of the Y(Co1-xNix)5 system were measured at 4.2 K in pulsed high magnetic fields up to 40 T. The spontaneous magnetization decreases linearly with increasing Ni concentration up to x=0.4. In the narrow concentration region 0.5≤x≤0.6, the magnetization rapidly decreases, but weak ferromagnetism persists up to x=0.8. On the other hand, the high-field susceptibility exhibits a maximum at x=0.55. These results show that the magnetic state of Y(Co1-xNix)5 changes from the high- to the low-moment state at the critical concentration x=0.55. In the vicinity of this concentration, the magnetization was measured at high pressures up to 1 GPa. The compound Y(Co0.5Ni0.5)5 shows a very large pressure effect, indicating that it is very close to the critical concentration