Berlin 2005 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

MA: Magnetismus

MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65

MA 20.65: Poster

Monday, March 7, 2005, 14:00–18:00, Poster TU C

Superparamagnetic behaviour of vortex cores. — •Robert Wieser, Natalia Kazantseva, Ulrich Nowak und K. D. Usadel — Fachbereich für Physik, Universität Duisburg-Essen

Magnetic vortices have been studied for a long time. The reviewed interest is triggered by the possibility of a direct observation of vortices in permalloy and Co magnetic nanodots. Such vortex structures are discussed in connection with high density data-storage and miniature sensors.

Earlier theoretical investigations in this regime have been done mostly at zero temperature. In this contribution we report on the thermodynamical behaviour of such vortex structures.

Our simulation based on Langevin dynamics show that the vortex core becomes superparamagnetic with increasing temperature. The energy barrier is estimated as difference between the energy of the in-plane vortex (all spins in plane) and the energy of the out-of-plane vortex (with central polarization). The barrier decreases with increasing core radius, which is given by the relation between dipol-dipol and exchange interaction.

Additional we found that with increasing temperature the magnetization inside the vortex core decreases faster than the magnetization outside the central region.

ACKNOWLEDGMENTS: Work supported by the Deutsche Forschungsgemeinschaft (SFB 491).