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 20.122: Poster

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

Ferromagnetic superexchange in Co doped TiO₂ — •Rebecca Janisch^1,2 and Nicola A. Spaldin² — ¹Institute for Electrical and Information Engineering, Technical University Chemnitz, 09107 Chemnitz, Germany — ²Materials Department, University of California, Santa Barbara, CA 93106, USA

The origin of ferromagnetism in dilute magnetic semiconductors is often discussed in terms of a competition between short-ranged antiferromagnetic superexchange interactions, and mechanisms which promote ferromagnetic order, such as carrier-mediated or RKKY interactions, double exchange and magnetic polarons. Indeed in conventional, tetrahedrally-bonded, semiconductor hosts such as GaAs or ZnO, this competitive picture is appropriate. However, in this presentation, we revisit the well-established Goodenough-Kanamori-Anderson rules to show that, in many other hosts, the superexchange mechanism leads to ferromagnetic coupling between the magnetic moments of neighboring transition metal dopants. We illustrate this behavior using ab-inito electronic structure calculations for Co-doped TiO₂ anatase, and propose a range of other semiconductor hosts in which the short-range interactions should be ferromagnetic.