Superconductivity in the ternary antimonide La₆ZnSb₁₅

Abstract

We discovered superconductivity in the ternary antimonide La 6 ZnSb 15 , and its superconducting properties were discussed through the resistivity, specific heat, and magnetization measurements. The crystal structure of La 6 ZnSb 15 is the orthorhombic La 6 MnSb 15 -type structure consisting of Sb sheets. Its electronic structure indicates that the conduction bands are mainly originated from Sb 5p orbitals in these Sb sheets. The electrical resistivity and magnetization measurements reveal that this compound is a type-II superconductor below 3.7 K. The upper critical field at zero temperature, µ 0 H c2 (0), is determined to be 851(8) mT. In the normal state, the electronic specific heat coefficient, γ, and the Debye temperature, Θ D , are found to be 18.8(8) mJ/mol K 2 and 218(1) K, respectively. From the electronic specific heat in the superconducting state, this compound belongs to a typical weak-coupling BCS superconductor.2

Ternary Rare-Earth Titanium Antimonides RE2Ti11 − xSb14 + x (RE = Sm, Gd, Tb, Yb)

“…The clear demarcation of RE 2 Ti 11x Sb 14 + x (RE ) Sm, Gd, Tb, Yb) from RE 2 Ti 7 Sb 12 (RE ) La, Ce, Pr, Nd) suggests that there are critical limits on the size of the RE atom. In both cases, the RE atoms are surrounded by antimony atoms in nine-coordinate geometry, but the RE-Sb distances decrease significantly from RE 2 Ti 7 Sb 12 (e.g., 3.205(1)-3.471(1) (The trend in size can be inferred from the Shannon-Prewitt (ionic) radii for RE 3+ (CN9), which decrease from 1.36 to 1.30 Å for La 3+ to Nd 3+ , 1.27 to 1.24 Å for Sm 3+ to Tb 3+ , and then to 1.18 Å for Yb 3+ . 16 The radius for Yb 2+ (only specified up to CN8) is 1.28 Å.)…”

“…Much of the current interest in ternary rare-earth antimonides relates to the search for new thermoelectric materials, 2 but they also display diverse electrical and magnetic properties. 3 Although systems containing a late transition metal are now relatively wellknown, those containing an early transition metal remain sparsely investigated.…”

“…In contrast to compounds of the lighter pnicogens, these antimonides tend to adopt structures containing polyhedra with higher CN (because of the large size of antimony) and with greater likelihood of disorder. Much of the current interest in ternary rare-earth antimonides relates to the search for new thermoelectric materials, but they also display diverse electrical and magnetic properties . Although systems containing a late transition metal are now relatively well-known, those containing an early transition metal remain sparsely investigated.…”

Structures and Physical Properties of Rare-Earth Zinc Antimonides Pr6Zn1+xSb14+y and RE6Zn1+xSb14 (RE = Sm, Gd−Ho)

“…The ternary phases known to date in this system are Yb 14 ZnSb 11 , − Yb 9 Zn 4+ x Sb 9 , RE Zn 2 Sb 2 ( RE = Eu, Yb), − RE Zn 1- x Sb 2 ( RE = La−Nd, Sm, Gd, Tb), − and RE 6 ZnSb 15 ( RE = La−Nd, Sm, Gd), the latter two possessing extended polyanionic Sb substructures. Among these, Yb 14 ZnSb 11 has been investigated for its thermoelectric properties, , and YbZn 2 Sb 2 and CeZn 1- x Sb 2 exhibit Kondo lattice behavior. , The RE 6 ZnSb 15 series is especially interesting because it and its Mn and Cu analogues have been the subject of detailed theoretical study in which a “retrotheoretical” approach is applied to understand the complex Sb substructures. ,, Moreover, La 6 ZnSb 15 has recently been found to be a type II superconductor ( T c = 3.7 K) . Although a full single-crystal X-ray diffraction study was performed on La 6 ZnSb 15 , only cell parameters were obtained for the remaining RE 6 ZnSb 15 members, which were assumed to be isostructural .…”

“…3,4,31 Moreover, La 6 ZnSb 15 has recently been found to be a type II superconductor (T c ) 3.7 K). 32 Although a full single-crystal X-ray diffraction study was performed on La 6 ZnSb 15 , only cell parameters were obtained for the remaining RE 6 ZnSb 15 members, which were assumed to be isostructural. 30 One of the unusual features in the structure of La 6 ZnSb 15 is the presence of a short Sb-Sb bond (2.831(2) Å) which links puckered Sb sheets together.…”