Novel ternary alkaline-earth and rare-earth metal antimonides from gallium or indium flux. Synthesis, structural characterization and 121Sb and 151Eu Mössbauer spectroscopy of the series A7Ga8Sb8 (A = Sr, Ba, Eu) and Ba7In8Sb8

Abstract

Reported are the synthesis and the structural characterization of the new ternary antimonides Eu(7)Ga(8)Sb(8), Sr(7)Ga(8)Sb(8), Ba(7)Ga(8)Sb(8), and Ba(7)In(8)Sb(8). They have been synthesized from reactions of the corresponding elements, using gallium or indium as metal fluxes. The four compounds are isostructural and crystallize with the space group P6(3)/mmc (no. 194) with lattice parameters as follows: a = 4.4942(8), c = 17.274(6) A for Eu(7)Ga(8)Sb(8); a = 4.5409(8), c = 17.486(4) A for Sr(7)Ga(8)Sb(8); a = 4.7045(12), c = 18.123(9) A for Ba(7)Ga(8)Sb(8); and a = 4.8274(3), c = 18.421(2) A for Ba(7)In(8)Sb(8). The temperature dependence of the magnetic susceptibility of Eu(7)Ga(8)Sb(8) confirms that the Eu ions are in the typical divalent state (Eu(2+)) with a room temperature effective magnetic moment mu(eff) = 8.02 mu(B). A phase transition from a paramagnetic to an antiferromagnetically ordered structure occurs in this material below 6 K. These results are corroborated by (151)Eu Mössbauer spectroscopy at 4.2 and 78 K, respectively. Eu(7)Ga(8)Sb(8), Ba(7)In(8)Sb(8) and the previously reported Sr(7)Ga(2)Sb(6) derivative of the cubic Th(3)P(4) type, were also investigated by (121)Sb Mössbauer spectroscopy.