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MA: Fachverband Magnetismus

MA 8: Magnetic Coupling Phenomena / Exchange Bias

MA 8.5: Vortrag

Montag, 23. März 2009, 16:15–16:30, HSZ 401

Monte-Carlo Study of Hysteretic Properties of Atomic Pairs and Triplets — •Elena Y. Vedmedenko, Jens Wiebe, and Roland Wiesendanger — University of Hamburg, Jungiusstr. 11, 20355 Hamburg

It has been recently demonstrated that the thermodynamic behavior of single magnetic atoms, atomic pairs and triplets on conducting substrates, which often possess giant magnetic anisotropy, may be successfully described in the framework of the Langevin dynamics [1,2]. As the Langevin distribution can be very well reproduced by means of Monte-Carlo simulations we have studied the hysteretic properties of single atoms and their ensembles in the framework of this technique. For the atomic pairs and triplets coupled by RKKY-type exchange interactions the time-averaged and time-resolved magnetization curves on each individual atom have been investigated. We demonstrate that the hysteretic behavior is very sensitive to the type of interaction (ferromagnetic or antiferromagnetic) as well as to magnetic surrounding, and is determined by the field-dependent paramagnetic switching of individual moments. The occupancy of two energy minima depends on the above mentioned parameters and varies for different atoms. The time-averaged Monte-Carlo data mimic recent experiments performed by spin-polarized scanning tunneling microscopy and reveal very peculiar magnetization curves, unusual for macroscopic magnets.

[1] P. Gambardella et al., Science 300, 1130 (2003) [2] F. Meier, L. Zhou, J. Wiebe, R. Wiesendanger, Science 320, 82 (2008)