We propose to investigate ultrafast, non-equilibrium spin dynamics triggered by femtosecond optical pulses and to exploit tailored nanoscale heterogeneities in magnetic systems to control their magnetic response on an ultrafast time scale. The heterogeneities are of three different types:
- Chemical: engineered multilayers of chemically distinct magnetic and non-magnetic materials lead to optimized optically induced spin currents, tuned interfacial spin orbit coupling and controlled interlayer exchange coupling. Lateral chemical inhomogeneities in ferrimagnets influence all optical switching (AOS).
- Magnetic: lateral nanoscale networks of magnetic domains act as a chemically homogenous spin-valve system to study fundamental properties of spin transport. Magnetic domain nucleation and growth upon laser excitation defines AOS.
- Excitation: tailored optical excitation via nanoscale metallic proximity masks gives a handle to control efficiency and lateral gradient of the optical stimulus and allows for subwavelength control of magnetic order.
Our main experimental tools will be ultrafast, broadband extreme ultraviolet (XUV) spectroscopy and resonant small angle scattering to capture a microscopic picture of the element-specific magnetization dynamics on the femtosecond time and nanometer length scale. These will be complemented by all-optical Kerr spectroscopy and microscopy.