SPIN-EXCHANGE BETWEEN ION PROBES AND LOCALIZED MOMENTS IN FERROMAGNETS AS THE ORIGIN OF TRANSIENT FIELDS

The transient field phenomenon has been ascribed to a polarization tra nsfer between the electrons of the ionic projectiles and the surplus o f majority spin electrons of the ferromagnetic host over the minority spin electrons. Earlier attempts to explain this crucial process faile d to account for the order of magnitude of the experimentally observed transient field strengths. A recent model which proposes spin exchang e scattering between bound projectile electrons and quasifree host ele ctrons as the mechanism of polarization transfer arrives at the correc t orders of magnitude but is in conflict with the weak velocity depend ence of the experimental polarization, exhibiting a strongly decreasin g behavior with increasing velocity. The new model presented here prop oses spin exchange between the ionic shell and localized electrons of the ferromagnet as a more adequate approach to the problem. It is show n that calculations involving hydrogenlike ions explain the size of th e experimentally observed polarization effects as well as their veloci ty dependence for various ion probes traversing thin iron foils.