Magnetism and Thermophysical Properties of Charge Transfer Complex
β′-(BEDT-TTF)(TCNQ)

The β′-type structure of (BEDT-TTF)(TCNQ) salt is known to show metal-insulator transition around 330 K. This salt belongs to a category of dimer-Mott system, where one hole localized on each BEDT-TTF dimer. We measured the magnetic susceptibility in a field of 1 T, and the heat capacity under 0 T, 1 T, and 3 T. We have observed anomaly around 3 K in the dependence of magnetic susceptibility as well as a broad hump of heat capacity. The moderate change of heat capacity with the increase of magnetic field demonstrates that this anomaly is associated with antiferromagnetic order in TCNQ layer. The magnetic entropy around 3 K is evaluated as 15~20% of Rln2 expected for the total entropy due to BEDT-TTF and TCNQ molecules. The thermodynamic data means that TCNQ layers and BEDT-TTF layers are not independent each other but have some correlations.

(by Y. Iwasaki & T. Yamamoto)

	Fig. 1. Temperature dependence of the heat capacity plotted as Cp T−1 vs. T2 plot of β′-(BEDT-TTF)(TCNQ) obtained under 0 T, 1 T, and 3 T.
	Fig. 2. Temperature dependence of the heat capacity of β′-(BEDT-TTF)(TCNQ) shown as Cp T−1 vs. T2 plot. The absence of any thermal anomaly and magnetic fields dependence is observable.