Magnetic Heat Capacities Of Kappa-(Bets)(2)Febr4 Measured By A Micro-Chip Calorimeter

Low temperature thermodynamic properties of kappa-(BETS)(2)FeBr4 are studied by using a tiny single crystal sample with 1 mu g adhered on a micro-chip calorimeter TCG3880. A large thermal anomaly associated with the antiferromagnetic transition of localized d electrons of Fe3+ was observed around 2.2 K. With the increase of magnetic fields applied parallel to the ac plane, the transition temperature shifts to lower temperature side accompanied by an anisotropic character. We found that the reduction of the transition temperature is largest, when magnetic field was applied parallel to a-axis. This observation is consistent with the previous result obtained by transport measurements which claimed that the spin easy axis is a-axis. The results demonstrate that the microchip calorimeter is effective for conducting thermodynamic measurements of molecular compounds. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim