Heat Capacity and Entropy of FeF2and CoF2from 11 to 300deg;K. Thermal Anomalies Associated with Antiferromagnetic Ordering

摘要

The heat capacities of FeF2and CoF2have been measured between 11 and 300deg;K. Both salts show anomalies in heat capacity associated with the antiferromagnetic ordering of the magnetic ions. The heat capacity of FeF2exhibits a sharp maximum of 17.8 cal degmdash;1molemdash;1at 78.35deg;K and that of CoF2has a maximum of 5.64 cal degmdash;1molemdash;1at 37.70deg;K. Values of the heat capacity, entropy, enthalpy, and free energy are tabulated at selected temperatures. The values of the entropy and enthalpy at 298.16deg;K are: FeF2,S0=20.79plusmn;0.04 cal degmdash;1molemdash;1,H0sngbnd;H00=3049plusmn;6 cal molemdash;1; CoF2,S0=19.59plusmn;0.04 cal degmdash;1molemdash;1,H0sngbnd;H00=2978plusmn;6 cal molemdash;1.