Dresden 2006 – scientific programme

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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.11: Poster

Tuesday, March 28, 2006, 15:15–19:15, P1

Temperature dependence of magnetization in GaMnAs — •Matthias Sperl, Janusz Sadowski, Rashid Gareev, Werner Wegscheider, Dieter Weiss, and Guenther Bayreuther — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany

Diluted magnetic semiconductors (DMS) based on III-V semiconductors doped with Mn have attracted a lot of interest recently. There is general agreement that ferromagnetism in these materials is caused by exchange interaction between Mn local moments mediated by holes.

In conventional ferromagnets thermally excited spin waves determine the temperature dependence of magnetization, M(T), well below the Curie temperature. This is to be contrasted with DMS materials where at low temperature spin-flip-like excitations are predicted [1] which lead to a steep decrease of the magnetization. M(T) should strongly depend on the homogeneity of the distribution of Mn ions in the lattice [1]. The aim of the present work is to experimentally study the influence of the Mn distribution on the appearance of spin wave-like excitations.

GaMnAs films with various Mn concentrations where grown on GaAs(100) and annealed under different conditions. M(T) was measured with a SQUID magnetometer. Experimental results on spin wave excitations will be discussed in comparison to theoretical predictions.

[1] M. Berciu, and R. N. Bhatt, Phys. Rev. B 66, 085207 (2002).