The Heat Capacity of FeCl2:4H2O between 0.4 deg. and 5.3 deg. K

摘要

The heat capacity, C(p), of polycrystalline FeCl2:4H2O has been determined between 0.42K and 5.34K in a He3-cooled vacuum calorimeter. A rounded Schottky anomaly was found with T(max) about 3K, confirming the earlier conclusion that the zero-field splitting of the Fe(++) ion ground state spin quintet is large with respect to the exchange energy. Two levels lie about 10K below the other three. Well below T(N) the presence of a gap in the excitation spectrum larger than about 2K T(N). A spin wave picture of these excitations provides a quantitative fit of C(p) up to 0.9T(N). (Author)