Magnetische 3d-Fremdatome und ihre Wechselwirkung in Kupfer, Silber und Palladium

Spin density functional theory and the KKR-Green's function method are used to calculate selfconsistently the electronic structure for magnetic 3d-impurities and magnetic 3d-impurity pairs in Cu, Ag and Pd. We calculate the local densities of states and the local moments for the magnetic impurities and for the ferro- andantiferromagnetic pair configurations. For the Pd-host the electronic structure of Cr, Mn, Fe, Co and Ni impurities is investigated for the impurity atom and several shells of surrounding host atoms. - Clusters up to 43 atoms are considered and correctly embedded in the host crystal. We found rather extended polarization clouds of roughly similar spatial form, which lead to the observed giant moments. Neglecting the perturbation of the neighbouring host atoms in Cu and Ag, we give a systematic overview of the magnetic impurity pair interaction for different interatomic impurity separations. We show that the magnetic interaction energy, i. e. the energy difference between the ferromagnetic and the antiferromagnetic pair configuration, can be estimated in first order from the difference of the single-particle energies of these configurations, calculated with the same frozen impurity potential. Contrary to these two site calculations host perturbations on neighbouring sites are selfconsistently included with the new method of constraints. We exert a longitudinal or transversal magnetic field on one of the impurities, which continuously changes the moment and transforms the configuration from ferromagnetic to antiferromagnetic. The total energy difference is calculated from the Hellmann-Feynman theorem by integrating over all intermediate constraining fields. Like the results of the 'frozen' potential method, these calculations show that two Fe-impurities on nearest neighbour sites in Cu couple ferromagnetically, whereas Mn-impurities or Cr-impurities couple antiferromagnetically. Finally we investigate the angle dependence of the magnetic pair interaction using the method of transversal constraints : We found that Mn- and the Fe-impurity pairs obey very well a cose-law as one should expect from a Heisenbergg-like interaction