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Lattice distortions in layered type arsenides LnTAs2 (Ln=La-Nd, Sm, Gd, Tb; T=Ag, Au): Crystal structures, electronic and magnetic properties |
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| Authors: | D Rutzinger M Doerr V Neu M Ruck |
| Institution: | a Anorganische Chemie, Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, D-01062 Dresden, Germany b Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden, Germany c Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, D-01187 Dresden, Germany d IFW Dresden, Institut für metallische Werkstoffe, Helmholtzstr. 20, D-01069 Dresden, Germany |
| Abstract: | The lanthanide coinage-metal diarsenides LnTAs2 (Ln=La, Ce-Nd, Sm; T=Ag, Au) have been reinvestigated and their structures have been refined from single crystal X-ray data. Two different distortion variants of the HfCuSi2 type are found: PrAgAs2, NdAgAs2, SmAgAs2, GdAgAs2, TbAgAs2, NdAuAs2 and SmAuAs2 crystallize as twofold superstructures in space group Pmcn with the As atoms of their planar layers forming zigzag chains, whereas LaAgAs2, CeAgAs2 and PrAuAs2 adopt a fourfold superstructure (space group Pmca) with cis-trans chains of As atoms. The respective atomic positions can be derived from the HfCuSi2 type by group-subgroup relations. The compounds with zigzag chains of As atoms exhibit metallic behaviour while those with cis-trans chains are semiconducting as measured on powder pellets. The majority of the compounds including 4f elements show antiferromagnetic ordering at TN<20 K. |
| Keywords: | Rare earth metal Arsenide Crystal structure Superstructure Resistivity Magnetic behavior Band structure |
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