Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 35: Magnetization / Demagnetization Dynamics II
MA 35.6: Vortrag
Mittwoch, 18. März 2015, 16:15–16:30, EB 301
Ultrafast changes in crystal field during the demagnetization of antiferromagnetic Cr2O3 — •Vera Giulia Sala1, Timothy Miller1, Stefano Dal Conte2, Valérie Véniard3, Giulio Cerullo2, and Simon Wall1 — 1ICFO - The Institute of Photonic Sciences, Av. Carl Friedrich Gauss 3, 08860 Castelldefels, Spain — 2Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy — 3École Polytechnique, 91128 Palaiseau cedex, France
While magnetization dynamics in ferro- and ferri-magnetic materials has received significant experimental attention, dynamics in antiferromagnetic systems has been less studied. This is because most optical techniques used to probe magnetism require a net magnetic moment for a signal to be observed, but antiferromagnets have no net magnetization. To overcome this issue we use time-resolved resonant second harmonic spectroscopy which is sensitive to the magnetic order in the room temperature antiferromagnet Cr2O3. Exciting the system with visible light causes charge transfer excitations which modify both the magnetic state and the resonance condition of the second harmonic process. By performing polarization analysis we can separate the dynamics of the magnetic state and the crystal field which sets the resonant conditions. By tuning the pump wavelength, we can control how strongly we drive the crystal field and find that the crystal field contribution can be reduced whilst still demagnetizing the system by the same amount. This opens the way to more efficient control of the magnetic state, where energy is coupled more selectively into the magnetic system than other degrees of freedom.