Synthesis, crystal and electronic structure, physical properties and 121Sb and 151Eu Mössbauer spectroscopy of the Eu14AlPn11 series (Pn = As, Sb)

The pnictides Eu 14 AlAs 11 and Eu 14 AlSb 11 were synthesized from the elements in sealed niobium ampoules. They crystallize in the tetragonal crystal system (Eu 14 AlAs 11 : a = 1627.6(2), c = 2180.0(4) pm; Eu 14 AlSb 11 : a = 1725.6(2), c = 2289.7(7) pm) with space group I 4 1 / acd , isostructural to Ca 14 AlSb 11 and can be described as Zintl phases. The Al atoms are surrounded by four pnictogen atoms, forming [AlPn 4 ] 9− tetrahedra. Additionally isolated Pn 3− anions and linear Pn 3 7− trimers can be found in the crystal structure. The compounds can be described according to (Eu 2+ ) 14 (AlPn 9− )(Pn 3− ) 4 (Pn 3 7− ). Eu 14 AlAs 11 and Eu 14 AlSb 11 both exhibit an antiferromagnetic transition at T N = 10.5(1) K and 12.5(1) K, respectively. For the antimonide, the magnetic transition has been confirmed by additional heat capacity measurements. Resistivity investigations indicate that Eu 14 AlSb 11 is a semiconductor with a band gap of E g = 0.28(5) eV close to room temperature. According to the Zintl formalism, the Eu atoms are divalent, which has been confirmed by magnetic susceptibility and additional 151 Eu Mössbauer spectroscopic studies. The measurements conducted at 6 K, below the magnetic ordering temperature, show a full hyperfine field splitting with complex spectra underlining the recorded magnetic data. Furthermore, 121 Sb Mössbauer spectroscopic studies have been conducted to study the different antimonide entities in the title compounds. Structure and property investigations of the Zintl phases Eu 14 AlAs 11 and Eu 14 AlSb 11 : magnetism, electrical resistivity, Mössbauer spectroscopy and theoretical calculations.