Structural And Physical Properties Of The5d Osmium Metallic Compounds(YbOs₂Al₁₀ And LaOsSi₃)

The research of this paper includes two aspects:a mixed Valence behavior in compound YbOs2Al10, structural and physical properties of the5d noncentrosymmetric LaOsSi3.LaOsSi3single crystals were synthesized for the first time by an arc melting method. The crystal is characterized by a tetragonal BaNiSn3-type structure (space group14mm) which lacks inversion symmetry along the crystallographic c-axis, isostructral with the intensively studied Rashba-type noncentrosymmetric superconductors LaRhSi3and LalrSi3. Unlike LaRhSi3and LalrSi3displaying superconductivity, LaOsSi3shows only metallic behavior over the measured temperature range of2-300K. The Sommerfeld coefficient y derived from specific heat is5.76mJ mol"1K"2, indicating that LaOsSi3has weak electronic correlation effect. The absence of superconductivity in LaOsSi3may lie in the Os5d bands in the electronic structure. If it is true, it would be useful to provide complementary knowledge in understanding the relation between conduction and the d bands of M in LaMSi3compounds (M=transition metals).Single crystals of YbOs2Al10and LuOs2Al10were grown for the first time using an aluminum self-flux method. The compounds crystallized into a cage-like structure in space group Cmcm, similar to the prototype compound YbFe2Al10. YbOs2Al10exhibited a mixed valence nature, as determined by magnetic susceptibility measurements over a wide temperature range from2K to900K, in which the inter-configuration-fluctuation model revealed a broad peak around400K. In contrast, LuOs2Al10displayed Pauli-like paramagnetic behavior over the same temperature range. Both compounds were metallic in nature between2K and300K. The electronic specific heat coefficient of21.25mJ mol-1K-2for YbOs2Al10was determined to be larger than that for LuOs2Al10(8.9mJ mol-1K-2), reflecting the mixed valence nature of the former. First-principles calculations predicted the presence of a mixed valence state in YbOs2Al10, in agreement with the experimental observations. The novel compound YbOs2Al10elucidates the evolution of the mixed valence nature of the Yb-based ternary transition metal aluminides from the3d to5d elements.