Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 6: Niederdimensionale Systeme (incl. Peierls-Übergang, organische Leiter, ...)

TT 6.5: Vortrag

Montag, 8. März 2004, 15:15–15:30, H18

ESR investigations of spin and charge ordering in quasi one-dimensional organic conductors — •Belal Salameh, Michael Dumm, Dieter Schweitzer, and Martin Dressel — Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart

Electron spin resonance (ESR) and SQUID measurements were performed on single crystals of the quasi one-dimensional organic charge-transfer salts (TMTTF)₂X (X = BF₄ and AsF₆) to investigate the low temperature electronic state. At high temperatures, the magnetic susceptibility of these compounds can be described by a spin 1/2 antiferromagnetic Heisenberg chain. Below the spin-Peierls transition in (TMTTF)₂AsF₆ (T_SP = 13K) and the anion-ordering (AO) transition in (TMTTF)₂BF₄ (T_AO = 41K) the magnetic susceptibility decreases exponentially indicating the non-magnetic nature of both ground states. We observed significant changes in the anisotropy of the ESR linewidth Δ H_pp below the charge-ordering transition in the AsF₆ salt (T_CO = 103 K) and the AO transition in the BF₄ compound. From these results the possible charge-ordering patterns at low temperatures can be estimated.