Seminars Archive

Magnetic scattering in reflection geometry - opportunities at FERMI.

Abstract
The spatial response of spin systems upon ultrafast laser irradiation is of general importance for understanding ultrafast spin transport processes. Especially interesting are the transport processes of hot electrons generated with ultrashort IR laser pulses. Those hot electrons have a high kinetic energy and can thus travel tens of nm distances within 100 fs which is the typical time scale of ultrafast demagnetization. Thus spatial transport of polarized spins is believed to be of importance for understanding the processes leading to ultrafast demagnetization. Some authors believe this to be even the dominant process in ultrafast demagnetization. In our previous work we could demonstrate that polarized spins are giving rise to a spatial response when diffusing across a domain wall into a minority spin area. The resulting time and length scales are in agreement with predictions from superdiffusive spin transport theory. However, those diffraction experiments were transmission experiments, which average the magnetic signal along the IR laser pulse direction. Depth resolved information along the IR beam direction is not available in such experiments. Here I want to discuss the use of X-ray reflectivity and diffuse scattering to probe the magnetic density profile along the IR beam direction of different multilayer systems. With this we envision to follow the full spatial evolution of spin density profiles on fs timescales. The corresponding spatial and temporal dynamics can yield new insights into the spin diffusion dynamics and will help to clarify (i) the physics of the transport processes itself and (ii) whether spin transport across magnetic and non-magnetic interfaces is of importance for demagnetization processes.