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Opto-magnetism and coherent control of spin dynamics in magnetic oxides

Andrei Kirilyuk 

Radboud University Nijmegen, Toernooiveld 1, Nijmegen 6525ED, Netherlands

Abstract

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. 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. Because the photons conserve their angular moments and loose only very small part of energy in the process, they can in principle participate in many consecutive excitation events.

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 magnetization in antiferromagnetic and ferrimagnetic oxides. The effect of such 100 fs optical pulse on a magnetic system was found to be equivalent to the effect of a magnetic field pulse with an amplitude of up to 1 T. In addition, different non-thermal mechanism was shown to simultaneously modify the magnetic anisotropy.

Coherent control of spin precession can be achieved by using multiple pulses in a rapid succession. Thus 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.
 

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Presentation: Invited oral at E-MRS Fall Meeting 2006, Symposium K, by Andrei Kirilyuk
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-22 10:37
Revised:   2009-06-07 00:44