Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Poster II

MA 33.4: Poster

Friday, March 26, 2010, 11:00–14:00, Poster B1

Ferromagnetic resonance study on highly doped (Ga_{1− x}Mn_x)As films — •Matthias Kiessling¹, Georg Woltersdorf¹, Vít Novák², and Christian Back¹ — ¹University of Regensburg, Universitätsstrasse, 31, 93053 Regensburg, Germany — ²Institute of Physics ASCR, Cukrovarnická 10, Prague, 16253, Czech Republic

We studied highly doped (Ga_1−x,Mn_x)As films grown by low temperature molecular beam epitaxy (LT-MBE) having a Mn concentration of x = 12.5% and a nominal thickness of 20 nm. All samples were annealed in air for 6 hours at 160^∘C. SQUID measurements reveal Curie temperatures of about 184 K. Ferromagnetic Resonance measurements performed from 8 to 18 GHz show that the magnetic anisotropy is dominated in the temperature range (10 - 180 K) by a large uniaxial anisotropy (K_u) pointing along the [1-10] crystallographic direction. K_u = 1.64*10⁴ erg/cm³ at 35 K is an order of magnitude larger than the fourfold magnetocrytalline anisotropy. The frequency dependence of the FMR line width ΔH(ω) is used to study the magnetic relaxation. The Gilbert damping parameter α is found to be very small (α = 0.003 - 0.0044 at 60 K) compared to previous studies [1,2]. Inhomogeneous broadening of the line width ΔH(0) due to variation of the magnetic properties in the sample or due to two magnon scatter observed at 10 K decrease with increasing temperature. In order to distinguish between magnetic inhomogeneities and two magnon scattering measurements are performed in the perpendicular configuration. [1] J. Sinova, PRB 69, 085209 (2004); [2] Y.H. Matsuda, Physica B 376-377, 668-671 (2006)