Effect of conduction electrons on the paramagnetic susceptibility of rare earth intermetallics

We have calculated the paramagnetic susceptibility of rare earth intermetallics in the model of the crystal-field 4f split 4f ions interacting with conduction electrons by exchange coupling. Using the thermodynamic perturbation theory we have derived analytical formulae for the susceptibility to the second order. We have developed scheme to simultaneously optimize fitting of crystal-field and coupling parameters to the experimental data.