Diana Guenzburger

Self-consistent cluster calculations of local magnetic properties of Fe-Ni alloys

Abstract The discrete variational method and the local exchange approximation were used to calculate the electronic structure of 19 atom embedded clusters representing Fe-Ni alloys of fcc structure. Magnetic moments and hyperfine fields were derived from the calculations and compared to experiment. We find that the observed reduction of H c compared to pure iron is not due to reduced Fe moments, but instead due to a change of sign of the conduction electron (4s) contributions.

Local magnetism of Fe impurities in non-transition metal hosts

Abstract First-principles local spin density calculations were performed for clusters representing an Fe impurity in Be, Mg, Ca, Sr and Al. Magnetic moments on Fe were obtained. Be Fe was found to be non-magnetic; Fe in Mg, Ca and Sr was found to have a moment > 2μB. The magnetic moment of Fe in Al was found to be quenched, if relaxation of first neighbors is considered.

Competition between the Cr3+−Gd3+ direct exchange and superexchange in Cr doped GdAlO3

Abstract The temperature dependence of the fluorescence spectrum of Cr3+ diluted impurities in GdAlO3 and the magnetic Franck-Condon effect observed in this system indicate that the exchange coupling constant JE between Cr3+ in the 2E excited state and Gd3+ is very small, in the sense that |JE|≪Jg, where Jg is the exchange coupling constant between Cr3+ in the ground state 4A2 and Gd3+. Here this is interpreted as resulting from a cancellation between the ferromagnetic direct Cr3+-Gd3+ exchange interaction and the antiferromagnetic superexchange which takes place through the oxygen ions.