MAGNETIC PHASE-DIAGRAM OF TBRU2SI2

Neutron diffraction experiments have been made on a single crystal sam ple of TbRu2Si2 under magnetic fields up to 40 kOe and in a temperatur e range from 4.2 to 60 K. The compound is a metamagnet with two-step m agnetization process. For H = 0 it has a high-order commensurate struc ture with a wavevector k = (0. 23, 0, 0). At an intermediate field the structure changes to a two-dimensional high-order commensurate one wi th wavevectors of k = (0.23, 0, 0), (0, 0.23, 0), (0.23, +/- 0.23, 0) and k = 0, and at a high field the compound becomes ferromagnetic. Sch ematic representation of the magnetic structures and a field-temperatu re phase diagram are presented.