Ultrafast element-specific magnetization dynamics of complex magnetic materials on a table-top

Highlights: ► We use X-ray pulses from high-harmonic generation to study element-specific magnetic dynamics. ► We elucidate the timescale of the exchange interaction in multi-sublattice magnets. ► Ultrafast superdiffusive spin currents induce femtosecond magnetization dynamics. -- Abstract: We review recent progress in femtosecond magnetization dynamics probed by extreme ultraviolet pulses from high-harmonic generation. In a transverse magneto-optical Kerr geometry, we established an ultrafast, element-specific experimental capability – on a table-top – for the measurement of magnetization dynamics in complex multi-sublattice magnets and multilayer magnetic structures. We show that this newly introduced technique is an artifact-free magnetic sensor, with only negligible non-magnetic (optical) contributions from the transient variation of the refractive index due to the presence of a non equilibrium hot-electron distribution. We then use these new experimental capabilities of ultrahigh time-resolution, combined with element-specific simultaneous probing, to disentangle important microscopic processes that drive magnetization dynamics on femtosecond timescales. We elucidate the role of exchange interaction on magnetization dynamics in strongly exchange-coupled alloys, and the role of photo-induced superdiffusive spin currents in magnetic multilayer stacks