Low temperature Mössbauer study and magnetic susceptibility measurements on YbMo6S8 and TmMo6S8

Abstract
Mössbauer study on Yb170 and magnetic susceptibility measurements show that YbMo6S8 contains both Yb2+ and Yb3+ ions with nearly equal proportions. The Yb2+ ions are submitted to a very strong electric field gradient with axial symmetry and move preferentially in the plane perpendicular to the gradient axis (which is probably the hexagonal axis c). The Yb3+ magnetic moments order perpendicularly to the c axis below TN=2.75 K and their magnitude is 1.7 μB near zero Kelvin. Ytterbium impurities also appear as Yb2+ and Yb3+ ions in TmMo6S 8, where the Yb3+ g-tensor is slightly anisotropic (g ∥ = 2.32, g⟩ = 3.64). Tm 169 Mössbauer measurements on TmMo6S8 show that only one Tm site is present