MAGNETIC BEHAVIOUR OF ISOLATED NICKEL AND COPPER IMPURITIES IN ALKALI ELEMENTS

Abstract
The magnetic behaviour of isolated nickel and copper impurities in various alkali elements is studied via hyperfine field measurements using the PAD-method. The Ni impurities exhibit strong local moments in nearly all alkali metals, but are non-magnetic in Li and in the alkali earths Ba and Ca. The temperature dependence of the paramagnetic enhancement factor of Ni in Rb and K nicely follows a Curie-Web-law. The extreme large positive saturation hyperfine field extracted from the Curie constant can only be explained by a nearly unperturbed spin-orbit coupled 3d⁹-configuration of localized 3d-electrons. For Ni in Na the paramagnetic enhancement factor is reduced and shows a maximum at room temperature. The Cu impurities in Cs exhibit non-magnetic behaviour which is expected from the most probable 3d¹⁰- configuration.