Yb_14-xTm_xMnSb₁₁ (0<x<0.5): Structure and magnetic properties

The compounds, Yb_14-xTm_xMnSb₁₁ (0<x<0.5), were synthesized as single crystals via Sn flux. The maximum amount of Tm was determined from wavelength dispersive microprobe analysis to be x=0.45 (1). Single crystal data are consistent with the Ca ₁₄AlSb₁₁ structure type and one formula unit can be described as consisting of 14 Yb²⁺ cations, MnSb₄ tetrahedron, Sb₃ linear anion and 4 Sb₃ ^- anions. The site occupancy of the Tm atom was not determined because of the small amount and small difference in scattering between Tm and Yb. The difference in bond lengths or angles between the solid solution and pristine Yb₁₄MnSb₁₁ is less than 1%. The magnetic susceptibility of samples prepared by Sn flux with the nominal composition of Yb _14-xTm_xMnSb₁₁ (x=0.1, 0.2, 0.3, and 0.4), show that these phases are ferromagnetic at low temperature with the T_C decreasing from 56 to 39 K with increasing x. Magnetic saturation for the x=0.4 composition at 5 K is consistent with Tm being present as Tm³⁺ and a negative magnetoresistance ratio (MR=[(ρ(H)-ρ(0))/ρ(H)]×100%) of 18% at 3 T is observed.