Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.28: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

An effective dimer-monomer model for the distorted diamond chain azurite (Cu₃(CO₃)₂(OH)₂) — •Sebastian Köhler¹, Bernd Wolf¹, Andreas Brühl¹, Mariano de Souza¹, Katarina Remović-Langer¹, Yeekin Tsui¹, Ulrich Tutsch¹, Jürgen Schreuer², and Michael Lang¹ — ¹Physikalisches Institut, Universität Frankfurt, D-60438 Frankfurt(M) — ²Institut für Mineralogie, Ruhr-Universität Bochum, 44780 Universitätsstraße 150

The S=1/2 spins in the natural mineral azurite (Cu₃(CO₃)₂(OH)₂) are connected to one-dimensional structures called distorted diamond chains. Given that all three exchange constants are antiferromagnetic, the distorted diamond chain is a simple realization of a one-dimensional frustrated spin system. The theoretically examined phase diagram at T=0 shows a ferrimagnetic, a dimerized and a spin-fluid phase. We present measurements of the specific heat as a function of temperature and magnetic field together with magnetic susceptibility data under hydrostatic pressure, which can be well interpreted using a simple model, where two of three spins in Azurite are connected to dimers in the singlet state (J_{intra−dimer}≈ 50 K), while the remaining monomer spins effectively form uniform, linear spin chains (J_eff= 7 K). Our experimental data support the description of Azurite for moderate magnetic fields in terms of the dimer-monomer model. In addition, the pressure dependence of the susceptibility directly indicates the large spin-phonon interaction in this low-dimensinal spin system.