Rare earth-rich compounds RE9TMg4 (RE = Y,Dy-Tm,Lu; T = Ru,Rh, Os,Ir) with an ordered Co2Al5-type structure |
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| Institution: | 1. Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstrasse 30, D-48149 Münster, Germany;2. Lebanese German University, Sahel-Alma Campus, Jounieh, Lebanon;1. Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via Cozzi 55, 20125 Milano, Italy;2. Institut Laue-Langevin, 71 avenue des Martyrs, 38000 Grenoble, France;3. Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy;4. ENEA, Dipartimento Fusione e Tecnologie per la Sicurezza Nucleare, via Fermi 45, 00044 Frascati, Italy;1. College of Chemistry, Jilin University, Changchun, 130026, PR China;2. Department of Chemistry, Tonghua Normal University, Tonghua, 134002, PR China;1. Lebanese German University, Sahel-Alma Campus, Jounieh, P.O.BOX 206, Lebanon;2. Université de Bordeaux, ICMCB-CNRS, Pessac, France;1. Karpenko Physico-Mechanical Institute, NAS of Ukraine, 5 Naukova St., 79601 Lviv, Ukraine;2. Hystorsys AS, P.O. Box 45, Kjeller NO-2027, Norway;3. Institut de Chimie et des Matériaux de Paris Est, CMTR, CNRS and U-PEC, 2-8 rue H. Dunant, 94320 Thiais, France;1. Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081, China;2. Inner Mongolia University of Science and Technology, Baotou 014010, China;3. College of Materials Science & Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China;4. China Rare Earth New Material (Weishan)Co., Ltd., Jining 277600, China |
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| Abstract: | The rare earth-rich intermetallic phases RE9TMg4 (RE = Y, Dy-Tm, Lu; T = Ru, Rh, Os, Ir) were synthesized by induction melting of the elements using sealed niobium ampoules as crucible material. The melted samples were additionally annealed in muffle furnaces and subsequently characterized by X-ray powder diffraction. The RE9TMg4 compounds adopt an ordered Co2Al5 type structure, space group P63/mmc. Four structures were refined from single-crystal X-ray diffractometer data: a = 953.71(5), c = 968.41(5) pm, wR2 = 0.00273, 603 F2 values, 21 parameters for Tm8.76RuMg4.24; a = 958.37(5), c = 975.66(5), wR2 = 0.00384, 661 F2 values, 20 parameters for Dy9OsMg4; a = 943.70(5), c = 967.91(5) pm, wR2 = 0.00430, 592 F2 values, 21 parameters for Tm8.74OsMg4.26; a = 968.09(5), c = 978.25(5) pm, wR2 = 0.0439, 623 F2 values, 21 parameters for Y9.18IrMg3.82. The compounds are prone to small homogeneity ranges (RE/Mg mixing). The transition metal atoms have tricapped trigonal prismatic rare earth coordination. These T@RE9 units (TP) are condensed with empty RE6 octahedra (O) via common triangular faces forming infinite strands with a sequence –TP–O–O–. These strands show the motif of hexagonal rod packing and they are separated by chains of edge- and corner-sharing tetrahedra. The magnesium substructures in the hexagonal Laves phase YMg2 and the prototype Y9CoMg4 are structurally closely related. Charge transfer trends, electronic band structures and bonding properties were studied within DFT. The resulting picture is that cobalt brings covalent character by reducing the overall charge transfer and modifies the Laves phase YMg2 by providing larger localization in the density of states. The Y–Co bonding in Y9CoMg4 prevails while weakening the Y–Mg bonds. The investigations of the magnetic properties of selected RE9TMg4 compounds revealed Pauli paramagnetic behavior for Y9CoMg4, Y9OsMg4 and Y9IrMg4. A ferromagnetic ground state with Curie temperatures of 46.0 and 47.6 K was observed for Dy9RuMg4 and Dy9OsMg4, respectively. Ho9RuMg4, Ho9OsMg4 and Tm9OsMg4 reveal antiferromagnetic ordering with Neél temperatures below 20 K. |
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| Keywords: | Intermetallic phases Rare earth-rich compounds Magnesium DFT calculations Magnetic properties |
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