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TT: Fachverband Tiefe Temperaturen

TT 16: Correlated Electrons: Low-dimensional Systems - Materials 1

TT 16.6: Vortrag

Dienstag, 24. März 2009, 10:45–11:00, HSZ 304

Magnetic properties of a novel quasi-2D Cu(II)-trimer system — •Bernd Wolf¹, Katarina Removic-Langer¹, Eiken Haussühl², Leonore Wiehl², Francesca Sauli³, Nils Hasselmann³, Peter Kopietz³, and Michael Lang¹ — ¹Physikalisches Institut, Universität Frankfurt, SFB/TR 49, D-60438 Frankfurt — ²Institut für Geowissenschaften, Universität Frankfurt, D-60438 Frankfurt — ³Institut für Theoretische Physik, Universität Frankfurt, SFB/TR 49, D-60438 Frankfurt

The rational design of low-dimensional quantum spin systems with novel exchange coupling topologies is of interest since it allows the testing of fundamental concepts in theoretical solid state physics. Up to now, only a few examples for 2D coupled-trimer systems are known. We have managed to synthesize a new magnetic Cu(II)-trimer system 2b*3CuCl₂*2H₂O (b = betaine), where the trimers form a quasi-2D quantum spin system with an unusual intralayer exchange coupling topology, which in principle supports ring-exchange processes. We discuss the structural aspects together with magnetic susceptibility and magnetization data. In addition, a theoretical model, enabling us to describe the magnetic properties over a wide temperature and field range is presented. The low-energy description and effective parameters are obtained from numerical calculations based on four coupled trimers. The model calculations indicate that for certain ranges of the inter-trimer coupling constants, which might be experimentally accessible, the low-energy properties of 2b*3CuCl₂*2H₂O will be dominated by non-trivial four-spin exchange processes.