Complex magnetic phase diagrams of TbCu2Si2 single crystal

The B-T magnetic phase diagrams for TbCu2Si2 single crystal, having the tetragonal ThCr2Si2-type crystal structure, have been constructed from magnetic measurements. The compound orders antiferromagneticaly below TN=11.9 K and shows another magnetic transition at Tt=9.1 K. In the easy magnetization direction of [110], a six-step metamagnetic process appears at low temperatures. Above Tt, it becomes a two-step metamagnetic one. There are seven ordered magnetic phases below the paramagnetic region in the B110-T magnetic phase diagram. In the [100] magnetization process, three metamagnetic transitions appear at low temperatures. The magnetization process becomes a one-step one above Tt. The B100-T phase diagram, composed of four phases, is very peculiar; a quad-critical point may appear. The magnetic structure for each phase has been discussed.