Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Correlated Electrons - Poster Session
TT 20.36: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
ESR investigations of the phase diagram of 2-dim organic conductors in the vicinity of the Mott-Hubbard transition — •Shadi Yasin, Michael Dumm, and Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany
In the two-dimensional layered organic charge-transfer salts κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1−x, it is possible to tune the electronic and magnetic properties by bandwidth control, i. e., by a systematic variation of the external or chemical pressure (anion size) as presented here. While the materials with low Br content x are antiferromagnetic insulators at low temperatures, the materials with high Br concentration show superconductivity. We studied the phase diagram in the vicinity of the Mott-Hubbard transition as a function of Br content by electron-spin resonance in the temperature range 4.2 K < T < 295 K along all three crystal axes. A detailed analysis of the ESR linewidth, the spin susceptibility and the microwave conductivity which was derived from the asymmetric Dysonian shape of the absorption lines was performed. These results enabled us to map the critical temperatures of the metal-to-insulator, antiferromagnetic and superconducting transitions for different Br dopings. We will also discuss the unconventional behaviour of ESR linewidth and spin susceptibility at temperatures below 50 K where the properties of the materials are dominated by strong electronic correlations.