Dresden 2006 – wissenschaftliches Programm

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MA: Magnetismus

MA 17: Magnetic Materials II

MA 17.9: Vortrag

Dienstag, 28. März 2006, 12:15–12:30, HSZ 401

Orbital magnetic moment anisotropy in (GaMn)As — •F. Kronast¹, R. Ovsyannikov¹, A. Vollmer¹, H.A. Dürr¹, W. Eberhardt¹, G.M. Schott², C. Ruester², C. Gould², G. Schmidt², K. Brunner², L.W. Molenkamp², and J. Cesar³ — ¹BESSY GmbH, Albert Einstein Strasse 15, 12489 Berlin, Germany — ²Physikalisches Institut III, Universität Würzburg, Germany — ³ESRF, BP 220, 38043 Grenoble Cedex, France

Using x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) we studied the ferromagentic ordering in (GaMn)As, the most prominent member of the III-V series of ferromagnetic dilute magnetic semiconductors (DMS). Mn replacing the trivalent Ga atoms provides a local spin magnetic moment and as an acceptor it creates itinerant holes [1]. The exchange coupling of holes to the Mn 3d shell by pd-hybridization mediates the long range ferromagnetic order. The pd-hybridization is usually assumed to be spherically isotropic [2].

Only recently Mahadevan et al. predicted a strongly anisotropic pd-hybridization due to p-d hopping interactions that depend on the specific lattice orientation (Phys. Rev. Lett., 93, 177201, 2004). In angle dependent XMCD measurements we find a variation of the Mn 3d orbital moment with the in-plane azimuthal lattice direction that is correlated with distinct spectroscopic features. Both can be interpreted by a spin-orientation dependent spatial anisotropy of the Mn acceptor state influencing the ferromagnetic ordering. This is the first experimental indication for an anisotropic pd-hybridization in (GaMn)As and, therefore, magnetic exchange coupling.