Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 32: Correlated Electrons - Low-dimensional Materials II
TT 32.5: Vortrag
Dienstag, 8. März 2005, 17:15–17:30, TU H2053
Sr2Cu(PO4)2 - an unexpected one dimensional spin 1/2 Heisenberg system with isolated CuO4 units — •Helge Rosner1, Michelle Johannes2, Johannes Richter3, and Stefan-Ludwig Drechsler4 — 1MPI for Chemical Physics of Solids, Dresden — 2NRL Washington, USA — 3Otto-von-Guericke-University Magdeburg — 4Leibniz Institute for Solid State and Materials Research Dresden
Recently, Belik et. al. [1] reported synthesis and physical properties of the compound Sr2Cu(PO4)2. The measured magnetic susceptibility [1] exhibits a broad maximum at 92 K characteristic for quasi-1D systems, but shows no long range magnetic ordering down to 0.45 K. Here, we present full potential electronic structure calculations within the local spin density approximation, followed by a subsequent mapping to a one-band tight-binding model and an extended Heisenberg model. Although the crystal structure of Sr2Cu(PO4)2 is formed by unlinked CuO4 units, we find a surprisingly pronounced one dimensional behaviour with substantial coupling between nearest neighbors (NN) only. The calculated NN exchange coupling J1∼180 K is in good agreement with the experimental estimate. It exceeds all other couplings by at least two orders of magnitude, placing the system in the forefront of 1D spin 1/2 model compounds. Model calculations using the derived exchange constants suggest that no long range magnetic ordering should be expected down to very low temperatures.
[1] Belik et. al., J. of Sol. Stat. Chem. 177, 883 (2004).