Multi-magnetic transitions in Tb<inf>2</inf>Mn<inf>3</inf>Si<inf>5</inf>

The results of ac magnetic susceptibility, dc electrical resistivity and thermoelectric power measurements on Tb2Mn3Si5 compound of Sc2Fe3Si5-type structure are reported in the temperature range 20-300 K. The compound is a paramagnet at room temperature and it undergoes a para- to ferrimagnetic transition at around 172±0.5 K (TC1) and enters the ferromagnetic region around 30±0.5 K (TC2). The resistivity shows an insulator to metal-type transition as the material goes from the disordered paramagnetic phase to the ordered magnetic phase. The thermopower is negative at room temperature and it crosses zero at around 132 K displaying a broad maximum centered at 65 K. These successive magnetic transitions are attributed to competitive Mn-Mn inter- and intralayer interactions, characteristic of the layered structure of the compound.