Specific heat and magnetisation of impurity Anderson model with non-Kramers doublet lowest state subject to the tetragonal crystalline electric field

The specific heat and the magnetisation of an impurity Anderson model, which has a non-Kramers doublet lowest state of an f² configuration subject to the tetragonal crystalline electric field, are investigated using the numerical renormalization group method. We examine two cases where the ground states of the system are non-Fermi-liquid (NFL) of two-channel Kondo type model and local-Fermi-liquid (LFL), respectively. In the former case the temperature dependence of the specific heat shows a broad peak which has an entropy, 0.5 ln 2, in the absence of the magnetic field. The specific heat shows two peaks in a very weak magnetic field: one has the same temperature dependence as in the absence of the magnetic field, the other at very low temperatures shows a release of the residual entropy, 0.5 ln 2. In the LFL case the specific heat shows only one peak which has an entropy, ln 2, in the absence of the magnetic field. The temperature dependence does not change in a very weak magnetic field. The γ-coefficient of the specific heat and the magnetic susceptibility never show - ln T dependence in the LFL case, even when the parameters are very close to the critical situation between NFL and LFL ground state.