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MA: Fachverband Magnetismus

MA 18: Poster I : Bio Magn. (1-2); Mag.Imgaging (3-9); Magn. Semiconductors (10-16); Half Metals & Oxides (17-20); Coupl.Phenomena (21-27); Magn. Mat. (28-41); Micro & Nanostr. Magn. Materials (42-61); Micro Magn. (62-64); Surface Magnetism (65-70); Transport Phenomena (71-85)

MA 18.16: Poster

Dienstag, 26. Februar 2008, 15:15–18:30, Poster E

volume dependence of the curie temperatures in diluted magnetic semiconductors — •brahim belhadji¹, lars bergqvist¹, silvia picozzi², and peter h. dederichs¹ — ¹Institut fuer Festkoerperforschung, Forschungszentrum juelich, D-52425 juelich, germany — ²Dipartimento di Fisica Universit degli Studi di L'aquila, Via Vetoio 10 L'aquila, Italy

Using electronic structure methods and statistical methods we

have studied theoretically the volume dependence of the

exchange interactions and Curie temperatutes in diluted

magnetic semiconductors. In both Mn-doped GaAs and Mn-doped

InAs, the calculated Curie temperatures from numerical exact

Monte Carlo simulations are more or less constant for a large

volume interval. We have compared the exchange mechanisms in

Mn-doped GaAs using both the local density approximation (LDA)

and the LDA+U method. It is demonstrated that the magnetic

properties are determined within Zener's p-d exchange model

for the LDA+U, while in LDA it is a mixture between double

and p-d exchange mechanisms. Moreover, it is shown that the

antiferromagnetic superexchange, which mostly affects the

nearest neighbour exchange couplings, becomes more

pronounced upon compression of the lattice.