Itinerant electron metamagnetism and related phenomena in Co-based intermetallic compounds (invited)

Abstract

Susceptibility and high field magnetization have been measured for Y(Co_1−xM_x)₂ (M=Al, Fe, and Ni). YCo₂ exhibits a metamagnetic transition at 69 T. Ni doping in YCo₂ increases the critical field (B_c), 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(Co_1−xAl_x)₂ with x≤0.11, the susceptibility is enhanced with Al and a sharp metamagnetic transition with lower B_c is observed. The susceptibility becomes maximum at a finite temperature T_max. B_c in the ground state is proportional to T_max. 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.