Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 19: Correlated Electrons: Low-dimensional Materials
TT 19.9: Vortrag
Dienstag, 28. März 2006, 16:00–16:15, HSZ 301
Mössbauer Study of the Fe(II) S=2 Spin Chain System K2Fe(C2O4)2 — •H.-H. Klauss1, F. Gouider1, F.J. Litterst1, S. Grossjohann2, A. Honecker2, W. Brenig2, and D.J. Price3 — 1IPKM, TU Braunschweig, Germany — 2IThP, TU Braunschweig, Germany — 3Department of Chemistry, U Glasgow, United Kingdom
Fe(II) in K2Fe(C2O4)2 is arranged in zig-zag chains in which the magnetic exchange is primarily mediated by the oxalate (C2O4)2- anions [1]. Mössbauer spectroscopy proves a well isolated orbital singlet ground state of the Fe in a very unusual trigonal prismatic local symmetry. Magnetic susceptibility measurements reveal a Curie-Weiss like behaviour at high temperatures and a broad cusp at 20 K consistent with dominant 1-D antiferromagnetic interactions. 3-D magnetic order is found below 7 K by Mössbauer spectroscopy. In the magnetic susceptibility an upturn is found below 7 K indicating a weak ferromagnetic component in the dominantly antiferromagnetically ordered state. Using Quantum Monte Carlo the magnetic susceptibility for a S=2 spin chain is calculated and compared with the experimental data. This results in an intrachain magnetic exchange constant of J||/kB≈6 K. From an RPA analysis of the 3-D ordering temperature the interchain magnetic exchange constant is estimated to be one order of magnitude smaller consistent with a dominant 1-D character of the magnetic interaction in this system.
[1] M.B. Hursthouse, M.E. Light, and D.J. Price, Angew. Chem. Int. Ed. 43 (2004) 472.