Large increase of magnetic hyperfine fields of 5sp-shell impurities in ferromagnets after vacancy trapping

Vacancy trapping by 119Sb impurities implanted in Ni, Co, and Fe gives rise to large changes of the magnetic hyperfine fields Bhf of the 119Sn daughter nuclei. We have measured the following values for the normal substitutional and the vacancy-associated impurity hyperfine fields (in T): In all cases, the vacancies associated with the impurities could be "frozen in" up to high temperatures by decoration with post-implanted helium atoms. The substantial increase of the fields can be understood in terms of the conduction-electron polarization model of Blandin and Campbell