Dresden 2003 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 27: Spinabh
ängiger Transport I

HL 27.7: Vortrag

Dienstag, 25. März 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. Waag² — ¹Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany — ²Abteilung Halbleiterphysik, Universität Ulm, 89069 Ulm, Germany

Dilute magnetic semiconductors such as Ga_1−xMn_xAs have attracted considerable attention recently, as they allow for all-semiconductor heterostructures with ferromagnetic properties. We discuss ferromagnetic resonance measurements of Ga_1−xMn_xAs thin films with a Mn content x=0.051. The resonance magnetic fields B_res are found to strongly depend on the orientation of the external magnetic field B₀ with respect to the sample normal, shifting from B_res≈ 0.1 T for B₀ in the plane of the thin film to B_res≈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 B_res, 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.