Regensburg 2000 – scientific programme

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AM: Magnetismus

AM 17: Oberflächenmagnetismus: elektronische Eigenschaften, reine Oberflächen

AM 17.8: Talk

Wednesday, March 29, 2000, 18:30–18:45, H22

Theory for laser control of ferromagnetic spin dynamics — •Ricardo Gómez-Abal and Wolfgang Hübner — Max-Plank-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle/Saale

We apply the Floquet theory to the study of the effect of a pulsed-laser on the spin-dynamics of a magnetic-system. We simulate the magnetic material by a two-level system. These two levels are coupled by a time-dependent term which consists of a pulse of arbitrary shape periodically repeated in time. Floquet theory allows to solve this kind of time-dependent interaction by diagonalizing the so-called Floquet matrix, which is a Hermitian operator in the space-time system of coordinates, as if it was a time-independent Hamiltonian. The eigenvalues and eigenvectors obtained give a complete description of the time evolution of the system. Within this simple model, we intend to understand the relationship between the shape of the pulse and the dynamics, aiming to find a way to control the spin-dynamics towards the possibility of technological applications. The effect of periodic application of the laser pulses, which is naturally included in Floquet therory and corresponds to high repetition rate pulsed-laser experiments, is also analyzed.