Hyperfine field systematics of nonmagnetic ions in ferromagnetic alloys

Hyperfine fields at interstitial and substitutional nonmagnetic ion sites in ferromagnetically ordered binary and tenary alloys have been studied within the framework of an extension of the phenomenological model due to Daniel and Friedel. It is concluded that the effects associated with the local Hartree potential of the impurity and the spin-split conduction band of the host are largely responsible for the observed systematic change of sign of the hyperfine field as a function of the impurity valence. The strong correlation noted by Balabanov and Delyagin between hyperfine fields and the atomic number of the impurity, in a fixed column of the periodic table, is shown to be largely due to the orthogonalization of the conduction electron wave functions to the occupied impurity core orbitals. Theoretical results for hyperfine fields at a large number of impurity sites in several ferromagnetic hosts are compared with the most recent experimental data and a number of predictions are given. The present charge screening model is critically compared with other theoretical model calculations and improvements that should be made on the present calculations are outlined.