Multi-magnetic transitions in Tb2Mn3Si5

The results of ac magnetic susceptibility, dc electrical resistivity and th ermoelectric power measurements on Tb2Mn3Si5 compound of Sc2Fe3Si5-type str ucture are reported in the temperature range 20-300 K. The compound is a pa ramagnet at room temperature and it undergoes a para- to ferrimagnetic tran sition at around 172+/-0.5 K (T-C1) and enters the ferromagnetic region aro und 30+/-0.5 K (T-C2). The resistivity shows an insulator to metal-type tra nsition 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-M n inter- and intralayer interactions, characteristic of the layered structu re of the compound. (C) 2001 Elsevier Science B.V. All rights reserved.