Calculation of magnetic properties and specific heat for the nuclear enhanced ferromagnet PrNi5

A general model hamiltonian for hyperfine enhanced magnetic materials is pr esented. the we of the model is not limited only to the nuclear I regime, h ut the model treats also situations when the strength of the exchange inter action is close to and above the threshold value. The I model is solved num erically for PrNi5 and the results are compared with recent ultra-low tempe rature experiments. In particular, the behavior of magnetization susceptibi lity, and specific heat of PrNi5d is studied for two external field geometr ies and anisotropic properties are pointed out, The effect of rite quadrupo le interaction is examined in detail. The question of the correlations amon g interacting ions is also addressed.