Blocking of iron magnetic moments and Spin density wave in FeTi2S4 and Fe2TiS4

Iron-titanium sulfides FeTi2S4 and Fe2TiS4 have been structurally and magnetically characterized using powder X Ray Diffraction with Rietveld refinement method and 57Fe Mössbauer spectroscopy at variable temperature. Both sulfides have the same crystallographic phase, based on the monoclinic Cr3S4 type structure and vary in atomic coordinates; FeTi2S4 retains the ideal atomic positions proposed for the Cr3S4 phase, while in Fe2TiS4 the metal displacements from ideal sites are noticeable. Mössbauer spectra reveal different magnetic behaviors; in FeTi2S4 there is a transition from paramagnetic to magnetic ordering at temperature Tc = 145 K, giving rise to unusually low hyperfine magnetic field of 2.5 T (at 77 K) if compared with values of iron magnetic moments reported previously, this behavior is explained on the basis of blocking Fe localized magnetic moments by the Spin density wave (SDW) originated from 3d Ti atoms. In Fe2TiS4 a transition from paramagnetic to (SDW) arises at Tc = 290 K, the SDW is spread in both Fe and Ti metals through [101] crystallographic plane and undergoes a transition of first order from Incommensurate SDW (ISWD) to Commensurate SDW (CSDW) at TIC = 255 K. The atomic positions in the unit cell are correlated to the magnetic behavior in both sulfides.