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Heat capacities of antiferromagnetic dimer-Mott insulators in organic charge-transfer complexes

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Abstract

Heat capacity measurements of quasi-two-dimensional Mott insulating compounds consisting of BEDT-TTF (bisethylendithiotetrathiafulubalene) donor molecules and counter anions were performed by the thermal relaxation calorimetry technique for single crystal samples. No distinct thermal anomalies at the predicted antiferromagnetic transition temperatures in κ-(BEDT-TTF)2Cu[N(CN)2]Cl (T N = 27 K) and β′-(BEDT-TTF)2ICl2 (T N = 22 K) were observed. These results demonstrate that the Mott insulating state of the organic salts which are dominated by the strong two-dimensional intra-layer antiferromagnetic interactions between neighboring S = 1/2 spins shows somewhat different features from the simple quasi-two-dimensional Heisenberg model with S = 1/2. The strong quantum fluctuations produced by the electron correlations suppress the long-range character of the spin correlations, which seems to be an important aspect of this kind of Mott insulating materials.

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  1. Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka, 560-0043, Japan

    S. Yamashita & Y. Nakazawa

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  1. S. Yamashita
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  2. Y. Nakazawa
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Correspondence to S. Yamashita.

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Yamashita, S., Nakazawa, Y. Heat capacities of antiferromagnetic dimer-Mott insulators in organic charge-transfer complexes. J Therm Anal Calorim 99, 153–157 (2010). https://doi.org/10.1007/s10973-009-0566-6

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