Calorimetric Study of Several Garnets at Low Temperatures

Abstract
Specific‐heat measurements on very pure polycrystalline samples of YIG, EuIG, and TmIG have been carried out between 0.4° and 4.2°K in zero external field. An analysis in terms of magnon and lattice contributions has been attempted for YIG. The dispersion parameter D appears to be lower than that measured for this same sample by NMR of the 57Fe nuclei, where D=30 cm−1. The results on EuIG determine the hfs field at the 151Eu and 153Eu nuclei near 0°K. This field was found to be 550±15 kOe, which is smaller than that from Mössbauer experiments. The nuclear specific heat of TmIG is in good agreement with that calculated from Mössbuaer experiments. Both EuIG and TmIG show only a small magnetic specific heat, as expected from susceptibility and magnetization measurements.