title: EuAu3Al2: Crystal and Electronic Structures and Spectroscopic, Magnetic, and Magnetocaloric Properties.
abstract: The intermetallic compound EuAu3Al2 has been prepared by reaction of the elements in tantalum ampules. The structure was refined from single-crystal data, indicating that the title compound crystallizes in the orthorhombic crystal system (a = 1310.36(4), b = 547.87(1), c = 681.26(2) pm) with space group Pnma (wR2 = 0.0266, 1038 F(2) values, 35 parameters) and is isostructural to SrAu3Al2 (LT-SrZn5 type). Full ordering of the gold and aluminum atoms was observed. Theoretical calculations confirm that the title compound can be described as a polar intermetallic phase containing a polyanionic [Au3Al2](δ-) network featuring interconnected strands of edge-sharing [AlAu4] tetrahedra. Magnetic measurements and (151)Eu Mössbauer spectroscopic investigations confirmed the divalent character of the europium atoms. Ferromagnetic ordering below TC = 16.5(1) K was observed. Heat capacity measurements showed a λ-type anomaly at T = 15.7(1) K, in line with the ordering temperature from the susceptibility measurements. The magnetocaloric properties of EuAu3Al2 were determined, and a magnetic entropy of ΔSM = -4.8 J kg(-1) K(-1) for a field change of 0 to 50 kOe was determined. Band structure calculations found that the f-bands of Eu present at the Fermi level of non-spin-polarized calculations are responsible for the ferromagnetic ordering in this phase, whereas COHP chemical bonding coupled with Bader charge analysis confirmed the description of the structure as covalently bonded polyanionic [Au3Al2](δ-) network interacting ionically with Eu(δ+).
authors.affiliation: Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstrasse 28/30, 48149 Münster, Germany.
authors.forename: Jan-Patrick
authors.initials: JP
authors.lastname: Schmiegel
authors.affiliation: Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstrasse 28/30, 48149 Münster, Germany.
authors.forename: Theresa
authors.initials: T
authors.lastname: Block
authors.affiliation: Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstrasse 28/30, 48149 Münster, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Gerke
authors.affiliation: Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstrasse 28/30, 48149 Münster, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Fickenscher
authors.affiliation: Institut für Anorganische Chemie, RWTH Aachen , Landoltweg 1, D-52074 Aachen, Germany.
authors.forename: Rachid St
authors.initials: RS
authors.lastname: Touzani
authors.affiliation: Institut für Anorganische Chemie, RWTH Aachen , Landoltweg 1, D-52074 Aachen, Germany.
authors.forename: Boniface P T
authors.initials: BP
authors.lastname: Fokwa
authors.affiliation: Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstrasse 28/30, 48149 Münster, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Janka