Hamburg 2001 – wissenschaftliches Programm
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AM: Magnetismus
AM 9: Poster: Magnetowid. (1-17), Dü. Schichten (18-34), Oberfl
ächenmag. (35,36), Mikr. Methoden (37-45), Mikromag. (46-58), Phasenüberg. (59-77), Spektroskop. (78-91), Nanokr.Mat.(92-96), Anisotrop. (97-101), Schmelzen(102-104),Sonst/postdeadl.(105-109)
AM 9.58: Poster
Dienstag, 27. März 2001, 14:45–19:00, Foyer S 3
Structure and Chemical Bonding in UAuGe — •Brendan Gibson1, Reinhard Kremer1, Ove Jepsen1, Jim Garrett2, Rolf-Dieter Hoffmann3, and Rainer Pöttgen3 — 1Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart — 2Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, L8S 4M1, Canada — 3Department Chemie, Ludwig-Maximilians-Universität, Butenandtstr. 5-13(Haus D), 81377 München
UAuGe crystallises in the hexagonal YPtAs type structure: P63/mmc, a=435.26(4) pm, c=1547.4(1) pm, V=0.2539(1) nm3. This may be considered as a superstructure with a quadrupled c axis of the well known AlB2 type. The gold and germanium atoms order on the boron positions and form 2D infinite puckered layers of Au3Ge3 hexagons with intralayer Au-Ge distances of 257 pm. Between adjacent layers the gold atoms have weak secondary Au-Au interactions with Au-Au distances of 327 pm. Ab initio calculations of the electronic band structure using the TB-LMTO method are presented. The bonding is illustrated by valence charge density and COHP plots which are compared with those of ScAuSi which has a similar structure with Au-Au interactions between the layers. The Au-Au bonding is however much weaker in UAuGe than in ScAuSi. Resistivity measurements exhibit a non-metallic temperature dependence. The increase in resistivity towards lower temperatures is uncharacteristic of intermetallic compounds, and may be fitted to a Curie-Weiss type formula suggesting a direct correlation to the magnetic ordering. A maximum in the resistivity is observed at T=26(1) K.