Berlin 2005 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

MA: Magnetismus

MA 9: FV-internes Symposium "Heusler-Legierungen" (Organizers: B. Hillebrands, H. Zabel)

MA 9.3: Invited Talk

Friday, March 4, 2005, 16:15–16:45, TU EMH225

Elementspecific electronic properties of the Heusler alloys investigated by X-ray absorption spectroscopy — •Hans-Joachim Elmers — Johannes Gutenberg Universität Mainz

Doped Heusler alloys and compounds of the Co₂(Y_xY′_(1−x))Z type are potential candidates for halfmetallic ferromagnetic materials that can be used in spintronic devices. The electronic properties can be tuned by varying Mn to Fe and Cr to Fe ratio x on the Y site. Of particular interest are properties at the surface of the material since all potential applications rely on electron transfer through an interface. In order to confirm theoretical investigations, that predict a gap in the minority bands, we performed X-ray absorption spectroscopy at the L_3,2 edges of the 3d transition metals of the pure compounds (x=0 and x=1) and alloys with varying composition x [1]. The determination of all photoemitted electrons (total yield) provides a moderate surface sensitivity (<10 nm). For in-situ cleaned bulk samples or in-situ capped surfaces we determine element specific magnetic moments. We compare our measurements with simulated spectra based on ab-initio bandstructure calculations. The absorption spectra show distinct features that can be related to the degree of disorder in the L2₁ - Heusler structure. The Cr moment is quenched in disordered areas of the sample because of a partly antiparallel alignment and therefore serves as a tracer signal for fully ordered unit cells. The comparison of XMCD spectra of Cr with simulated spectra indicates a high spinpolarization in ordered compounds.

[1] H. J. Elmers, S. Wurmehl, G. H. Fecher, G. Jakob, C. Felser, G. Schönhense, Appl. Phys. A 79, 2004, 557 and references therein.