MULTISTEP METAMAGNETISM OF TBRU2SI2 SINGLE-CRYSTAL

Measurements of magfietization and magnetic susceptibility have been c arried out on a tetragonal antiferromagnetic (T-N = 57 K) TbRu2Si2 sin gle crystal. Below 5 K, a multi-step, at least six steps, metamagnetic process appears along the easy c-axis. The saturation moment M(s) is 8.94 mu(B)/f.u. The smallest interval between two steps is 0.34 mu(B) (= M(s)/26). The process is briefly discussed by the self-consistent p eriodic exchange field model, suggesting the existence of a paramagnet ic plane owing to a singlet ground state.