Berlin 2012 – scientific programme

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MA: Fachverband Magnetismus

MA 30: Focus Session "Spin Currents in Magnetic Nanostructures", Organization: Mathias Kläui (Univ. Mainz)

MA 30.3: Invited Talk

Wednesday, March 28, 2012, 16:00–16:30, EB 301

Generation of superdiffusive spin-currents through femtosecond laser excitation of ferromagnetic/non-magnetic hybrid structures — •Peter M. Oppeneer¹, Marco Battiato¹, Karel Carva^1,2, and Pablo Maldonado¹ — ¹Uppsala University, S-751 21 Uppsala, Sweden — ²Charles University, 12116 Prague, Czech Republic

The process of femtosecond laser excitation in a metallic ferromagnet is analyzed theoretically. Laser excitation creates spin-polarized hot electrons with fast transport characteristics. We develop a semi-classical model for transport of such excited electrons, treating the multiple electronic collisions exactly /1/. The derived transport equation is solved numerically and it is shown that the spin-transport is neither diffusive nor ballistic, it is superdiffusive. Due to distinct lifetimes of majority and minority electrons effectively a spin-polarized current is created. Considering ferromagnetic/non-magnetic layer structures where the ferromagnetic layer is laser excited, and solving the resulting spin-dynamics numerically in the time-domain, we show that injection of a superdiffusive spin-current in the non-magnetic layer is achieved. The injected spin-current consists of hot, mobile majority spin electrons and is nearly 100% spin-polarized. It could be used as a means to accomplish domain wall movement or in spin-based electronics.
/1/ M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010).