METAMAGNETISM IN TBNI2SI2 SINGLE-CRYSTAL

We studied magnetic properties in the TbNi2Si2 single crystal compound by magnetic and neutron diffraction measurements. The magnetic moments born on only Tb are fixed to the c-axis due to a strong crystalline electric effect. The compound undergoes a commensurate-incommensurate phase transition at T(t) = 7.9 K; the commensurate phase with k=[1/2, 1/2, 0] is stable below T(t), and above T(t), the incommensurate one with k=[1/2+tau, 1/2-tau,0] (tau=0.074) appears and persists up to T(N)=14.6 K. A multi-step metamagnetic transition was found in the low temperature c-axis magnetization process in which at least nine magnetic phases appear. This process is a typical example of ''the devil's staircase'' in real compounds.