Magnetic and transport properties of Te doped Yb ₁₄MnSb ₁₁

A series of single crystal samples, Yb ₁₄MnSb _11-xTe _x (x ≤ 0.2), were investigated via Sn flux. The element distributions were mapped using an electron microprobe, which demonstrated inhomogeneity and limited solubility of Te in the crystals. The magnetic properties of two crystals of compositions Yb _13.80(2)Mn _1.03(1)Sb _11.11(4)Te _0.06(3) and Yb _13.82(3)Mn _1.02(1)Sb _11.02(8)Te _0.14(6) were investigated. Increasing amounts of Te increase the saturation moment of Yb ₁₄MnSb _11-xTe _x, and slightly lower the ordering temperature T _C by about 1 K. This is attributed to the filling of the hole in Yb ₁₄MnSb ₁₁ and the reduction of the screening of the Mn ²⁺ d ⁵ electrons, resulting in a higher effective moment. Hot-pressed, fully dense pellets of Yb _13.72(3)Mn _1.08(1)Sb _11.13(6)Te _0.07(5), Yb _13.76(5)Mn _1.11(1)Sb _10.96(8)Te _0.16(8), and Yb _13.76(4)Mn _1.10(2)Sb _10.95(9)Te _0.19(7) were prepared for thermoelectric property measurements. Both Seebeck coefficient and electrical resistivity increase with increasing amount of Te as a result of decreasing carrier concentration. Increasing amounts of YbTe with increasing x could be identified in the electron microprobe. The total thermal conductivity was approximately the same for all compositions, similar to that of Yb ₁₄MnSb ₁₁. The figure of merit zT reaches a maximum of 1.11 for x = 0.07 at 1240 K, which is approximately 12% higher than the parent compound, Yb ₁₄MnSb ₁₁.