Magnetic and structural phase diagram of Tb5(SixGe1-x)4 -: art. no. 094405

The different magnetic and crystallographic structures in the series of Tb-5(SixGe1-x)(4) compounds have been studied by means of macroscopic (ac magnetic susceptibility, linear thermal expansion, and resistivity) and microscopic neutron powder diffraction experiments. As a result, the magnetic-crystallographic temperature-composition phase diagram has been determined over the whole temperature range (2-300 K). We have described in detail the origin of the low-temperature magnetic transitions in pure Tb5Ge4 and Tb5Si4 alloys. Compounds with x = 0.4, 0.5, and 0.6 present a monoclinic (P112(1)/a) structure at room temperature. On cooling down, these materials exhibit a first-order crystallographic-magnetic transformation to an orthorhombic (Pnma) canted-ferromagnetic structure. These results constitute an experimental evidence of the strong coupling between crystallographic and magnetic degrees of freedom in the Tb-5(SixGe1-x)(4) compounds.