18.05.2006 |
Opto-magnetism and coherent control of spin dynamics
Dr. Andrei Kirilyuk, Radboud University Nijmegen, The Netherlands
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The ever-increasing demand for the density and speed of information storage has triggered an intense search for ways to control the magnetization of a medium by means other than magnetic fields. The control of magnetism by light is one of the potential approaches to this problem since a laser pulse is one of the shortest man-made events, shorter than 10-14 seconds. It has been shown how femtosecond laser pulses can thermally change the magnetization on a sub-picosecond time scale.
Far more exciting is the possibility of the non-thermal control of spins. This is possible, for example, via the nonlinear inverse Faraday effect, which does not require absorption and is based on a Raman-like coherent optical scattering process.
In this talk I will consider such opto-magnetic effects and demonstrate, how circularly polarized femtosecond laser pulses can nonthermally excite and coherently control the spins in antiferromagnetic and ferrimagnetic materials. The effect of such an ultrashort optical pulse on a magnetic system was found to be equivalent to the effect of a similarly short magnetic field pulse with an amplitude of up to 1 T. Coherent control of spin precession can be achieved by using multiple pulses in a rapid succession. For example, the precession can be amplified or stopped by sending a second pump pulse even or odd number of half-periods after the first one. Note that in the case of stopping, the energy of magnetic precession is taken away by the light pulse, which is an equivalent of the magnetic cooling.
Einladender: Prof. Dr. S.O. Demokritov
| Ort: |
Wilhelm-Klemm-Str. 10, IG I, HS 2 |
| Zeit: |
donerstags 16 Uhr c.t. |
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Kolloquiums-Kaffee ab 15:45 Uhr vor dem Hörsaal |
Im Auftrag der Hochschullehrer des Fachbereichs Physik
Prof. Dr. S. Demokritov
