Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.40: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

The use of hydroquinone-derived linkers for the design of low-d spin systems: from isolated dimers to Heisenberg chains — •Bernd Wolf¹, Andreas Brühl¹, Jörg Magerkurth¹, Volodymyr Pashchenko¹, Bernhard Brendel¹, Michael Lang¹, Günter Margraf², Hans-Werner Lerner², Tonia Kretz², and Mathias Wagner² — ¹Physikalisches Institut, Universität Frankfurt, 60054 Frankfurt, FOR 412 (Germany) — ²Institut für Anorganische Chemie,

In the course of an interdisciplinary research program to synthesize new classes of molecule-based quantum magnets which enable their fundamental physical properties to be explored systematically upon variations of physical or chemical parameters, we have produced a series of low-dimensional quantum-spin systems. The materials are all based on hydroquinone-derived linkers connecting Cu²⁺ ions carrying a spin of S = 1/2. The measurements of magnetic, magnetothermal and magnetoelastic properties cover wide ranges of temperatures 0.06 K < T < 320 K and magnetic fields B < 50 T. Especially for a 1-D Heisenberg antiferromagnet with a moderate magnetic coupling constant we have been able to perform experiments across the saturation field g µ _B B_S = 2|J| which marks, at T = 0, the endpoint of a quantum-critical line in the B-x plane. It has been found that crossing B_S is accompanied by a distinct magnetocaloric effect. In addition, a pronounced acoustic anomaly has been observed close to B_S and identified as a generic property of the uniform antiferromagnetic Heisenberg chain with a finite spin-lattice coupling.