Specific Heat and Susceptibility in Chromium Methylammonium Alum above the Critical Temperature

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Abstract
The specific heat and susceptibility of chromium methylammonium alum is calculated above the critical temperature. The method is based on a high-temperature expansion of the partition function in the presence of a crystal field, using a Laplace transform. The results are worked out in first (for the susceptibility) and second (for the specific heat) order in the coupling Hamiltonian. The summation over the four different sublattices is worked out for the two different crystallographic phases which seem to occur above and below 170 K. The lack of rotation symmetry of the crystal field in its local reference system, which was found by paramagnetic resonance, is taken into account. The result for the susceptibility is given explicitly in Eq. (4. 18a) as a function of a reduced temperature.