Thermodynamic and magnetic properties of knorringite garnet (Mg3Cr2Si3O12) based on low-temperature calorimetry and magnetic susceptibility measurements

Abstract

The low-temperature heat capacity of knorringite garnet (Mg3Cr2Si3O12) was measured between 2 and 300 K, and thermochemical functions were derived from the results. The measured heat capacity curves show a sharp lambda-shaped anomaly peaking at around 5.1 K. Magnetic susceptibility data show that the transition is caused by antiferromagnetic ordering. From the C p data, we suggest a standard entropy (298.15 K) of 301 ± 2.5 J mol−1 K−1 for Mg3Cr2Si3O12. The new data are also used in conjunction with previous experimental results to constrain ∆H f ° for knorringite.