Heat capacity and phase transition of a five-coordinated antiferromagnet, IODOBIS ( N,N-diethyldithiocarbamato) iron (III), in the temperature range from 0.4 TO 300 K

Abstract

The heat capacity of iodobis ( N, N-diethyldithiocarbamato) iron (III) has been measured between 0.4 and 300 K. A phase transition from an antiferromagnetic to a paramagnetic state was found at T N = (1.937 ± 0.010) K, and a Schottky-type anomaly arising from a zero-field single ion splitting was observed around 12 K. The total magnetic entropy and enthalpy, including the phase transition and the Schottky-type anomaly, are 11.36 JK −1 mol −1 and 134.5 J mol −1, respectively. The entropy is approximately equal to R ln 4 ( = 11.53 JK −1 mol −1), confirming that the spin manifold is really a quartet. The entropy and enthalpy due to the phase transition are estimated to be (5.57±0.01) JK −1 mol −1 and (13.2±0.05) Jmol −1, respectively. The entropy and enthalpy above t n are quite large, as in the case of the related compound chlorobis ( N, N-diethyldithiocarbamato) iron (III). This fact suggests that the present complex may be considered to have a two-dimensional type of magnetic structure from a thermodynamic point of view. A correlation diagram between the transition entropy and energy is proposed, this being a diagnostic for the determination of the magnetic dimensionality.