ITINERANT-ELECTRON METAMAGNETISM AND RELATED PHENOMENA IN CO-BASED INTERMETALLIC COMPOUNDS (INVITED)

Susceptibility and high field magnetization have been measured for Y(Co1-xMx)2 (M=Al, Fe, and Ni). YCo2 exhibits a metamagnetic transition at 69 T. Ni doping in YCo2 increases the critical field (Bc), while Fe doping decreases it. These changes can be elucidated with the band picture of metamagnetism. B c of YCo2 exhibits a positive shift proportional to the square of temperature. In the paramagnetic region of Y(Co1-xAl x)2 with x≤0.11, the susceptibility is enhanced with Al and a sharp metamagnetic transition with lower Bc is observed. The susceptibility becomes maximum at a finite temperature Tmax. B c in the ground state is proportional to Tmax. These experimental results are discussed with a new theory based on a spin fluctuation model. The susceptibility and the metamagnetic transition are found to be very sensitive to pressure.