The Evolution of the Antiferromagnetic Structure of the Terbium Titanium Oxysulfide Tb2Ti2S2O5 between 5K and 1.4K
The Tb2Ti2S2O5 compound belongs to the lanthanide titanium oxysulfides family Ln2Ti2S2O5. The 3D-structure can be schematically described as a 2D-stacking of [Tb2S2] layers alternating with [Ti2O5] ones. The magnetic structure of this compound was determined from neutron diffraction experiments on a powder sample in the 1.4 K - 15 K temperature range. An incommensurate antiferromagnetic long-range order (LRO) occurs at temperatures ranging from 4.1 K to 2.9 K, which turns to a commensurate state below 2.4 K. The evolution of the propagation vector from ki, ⃗ (kx,0,0), kx ≈ 0.46 to kc, ⃗(1/2,0,1/2) is quite unusual. The origin of this unusual change in direction of the propagation vector is not yet explained. On the other hand, a quite large part of the total magnetic moment is involved in a short range ordering (SRO). The refinement procedure taking into account the different coexisting magnetic phases leads to a smooth variation of the total magnetic moment versus temperature.
Yvonne Andersson, Eric J. Mittemeijer and Udo Welzel
A. Lafond et al., "The Evolution of the Antiferromagnetic Structure of the Terbium Titanium Oxysulfide Tb2Ti2S2O5 between 5K and 1.4K", Materials Science Forum, Vols. 443-444, pp. 387-390, 2004