Femtomagnetism

Technology is approaching the fundamental length scales to which devices can be shrunk, but there remain orders of magnitude of possible improvements in the time domain, where operations occur in tens of picoseconds or slower. Many proposals for improvement in time involve the manipulation of spin. Meanwhile, spin structure and dynamics are the least understood aspects of many systems yet underlie far-ranging proposed applications from spintronics and quantum computing to energy-efficient magnetocaloric refrigerators. Intriguing observations of spin order control in ferromagnets using femtosecond-scale laser pulses raises the possibility of magnetic data reading and writing with very little energy used.

The one-of-a-kind spin-TOF spectrometer (see Spin-ARPES) can be used with the pump-probe technique (see Time-Resolved ARPES) to directly study ultrafast spin dynamics in ferromagnetic systems. Watching the evolution of the spin-dependent electronic bandstructure during these processes with the spin-ARPES system would aid our understanding of this odd behavior of relatively simple magnetic systems.

We are currently in the process of assembling the optics for a pump-probe system for the spin-TOF chamber. We hope to soon be able to take time- and spin-resolved data on ferromagnetic materials. The spin-TOF’s rapid data acquisition will be crucial for studying the added experimental variable of time delay between pump and probe pulses.

The cartoon at right demonstrates one way in which lasers have been shown to control magnetic order in ferromagnets. Left- and right-circularly polarized light are seen to deterministically reorient the magnetization of a sample after sending it through a non-equilibrium phase. This, and other ultrafast magnetic effects are reviewed in Kimel et al. Laser & Photon. Rev. 1, 3 (2007).


Selected Publications

(Please see Journal Articles for a more complete list.)

Mapping the spin-dependent electron reflectivity of Fe and Co ferromagnetic thin films
J. Graf, C. Jozwiak, A.K. Schmid, A. Lanzara
Phys. Rev. B 71, 144429 (2005).

Magnetic properties of Fe/NiO/Fe(001) trilayers
P. Biagioni, A. Brambilla, M. Portalupi, N. Rougemaille, A. K. Schmid, A. Lanzara, P. Vavassori, M. Zani, M. Finazzi, L. Duo, F.Ciccacci
J. Magnetism and Magnetic Materials290-291, 153-156 (2005).

Perpendicular Magnetic Coupling in Fe/NiO/Fe(001) Trilayers Studied by Spin Polarized Low Energy Electron Microscopy
M. Portalupi, G. H. Gweon, C. Jozwiak, J. Graf, A. K. Schimd and A. Lanzara
Journal of Microscopy and Microanalysis (2004).