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DPG

Dresden 2003 – scientific programme

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HL: Halbleiterphysik

HL 27: Spinabh
ängiger Transport I

HL 27.7: Talk

Tuesday, March 25, 2003, 18:45–19:00, BEY/154

Ferromagnetic Resonance in (Ga,Mn)As — •S.T.B. Goennenwein1, T. Wassner1, H. Huebl1, T. Graf1, M. S. Brandt1, M. Stutzmann1, A. Koeder2, S. Frank2, W. Schoch2, and A. Waag21Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany — 2Abteilung Halbleiterphysik, Universität Ulm, 89069 Ulm, Germany

Dilute magnetic semiconductors such as Ga1−xMnxAs have attracted considerable attention recently, as they allow for all-semiconductor heterostructures with ferromagnetic properties. We discuss ferromagnetic resonance measurements of Ga1−xMnxAs thin films with a Mn content x=0.051. The resonance magnetic fields Bres are found to strongly depend on the orientation of the external magnetic field B0 with respect to the sample normal, shifting from Bres≈ 0.1 T for B0 in the plane of the thin film to Bres≈0.9 T for B0 perpendicular to the film. Moreover, for the latter orientation of B0, up to ten resonances can be resolved. We show that these can be identified as spin wave resonances. Both the non-quadratic spacing of the spin wave modes, as well as the strong angular dependence of Bres, can be quantitatively understood in terms of a linear gradient in the magnetic properties across the film thickness. We will discuss possible origins of this magnetic gradient and show that from these measurements, the exchange interaction between Mn moments can be deduced.

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