MAGNETIC PHASE-DIAGRAM OF TBGA2

Magnetization measurements on a single crystal, powder neutron diffrac tion experiments and specific heat on the hexagonal TbGa2 compounds ar e presented. Below T-N = 18.5 K, multistep metamagnetic transitions ar e observed when the field is applied perpendicular to the [001] hard m agnetization axis. The H-T magnetic phase diagrams along the [100] and [120] directions were deduced. At any temperature below T-N, the magn etic structure is described with the incommensurate propagation vector Q = (1/3, 1/3, 0.189). From the neutron diffraction experiments three possible magnetic structures are deduced, among them a triangular str ucture modulated along c being the most likely.