Integral equations for thermodynamic quantities are derived in the framework of the non-crossing approximation (NCA). Entropy and specific heat of 4f contribution are calculated without numerical differentiations of thermodynamic potential. The formulation is applied to systems such as PrFe4P12 with singlet-triplet crystalline electric field (CEF) levels.
@article{arxiv.cond-mat/0510424,
title = {Self-Consistent Perturbation Theory for Thermodynamics of Magnetic Impurity Systems},
author = {J. Otsuki and H. Kusunose and Y. Kuramoto},
journal= {arXiv preprint arXiv:cond-mat/0510424},
year = {2015}
}