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Magnetization dynamics

Magnetization dynamics. Only x-rays combine sub-ns time resolution with sub 100nm spatial resolution!. Magnetism: The reservoirs. The fundamental interactions. The micromagnetic picture. fs to ps dynamics. Very complex Time scale: 100ps to years. The two dynamic regimes.

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Magnetization dynamics

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  1. Magnetizationdynamics

  2. Only x-rays combine sub-ns time resolution with sub 100nm spatial resolution!

  3. Magnetism: The reservoirs The fundamental interactions The micromagnetic picture fs to ps dynamics Very complex Time scale: 100ps to years

  4. The two dynamic regimes Ultrafast demagnetization Precession and damping E. Beaurepaire, et al.,Phys. Rev. Lett. 76, 4250 (1996)

  5. Time resolved MOKE

  6. Thesample

  7. Directobservation of theprecession Y. Acremann et al., Science 290, p492 (2000)

  8. Magneticeigenmodes

  9. Time Resolved Photo Emission Electron Microscope Pump laser beam Electron optics Auston switch Synchrotron radiation

  10. Response to the magnetic field pulse 10 m Magnetic field pulse (~300 ps in the beginning ) Observation x-rays

  11. Hidden Parameter in the Domain Structure Choe et al., Science 304, 420 (2004).

  12. Vortex at the domain wall crossing

  13. Response to a fast field pulse H slow fast (<1ns) The response to a fast pulse is determined by the precession of the magnetization, not by relaxation!

  14. Vortex moves parallel or antiparallel to the applied field direction As the vortex drags the domain wall, it determines the dynamics of the whole domain structure!.

  15. Scanning transmission x-ray microscopy (STXM) • Spatial resolution: 30nm • Temporal resolution: 70ps • Elemental selectivity • Magnetic contrast

  16. Imaging magnetism with x-rays:X-ray Magnetic Circular Dichroism (XMCD) Transition Metal (e.g. Fe, Co, Ni) Core  Valence excitation of electrons Polarization dependent absorption of x-rays Depends on: number of holes, spin and orbital moment

  17. Switching of thevortexcore Van Waeyenberge et al., Nature 444, 461 (2006).

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