Ultrafast Demagnetization Measurements using Extreme Ultraviolet Light: Comparison of Electronic and Magnetic Contributions

Ultrashort pulses from high-harmonic generation provide new capabilities for uncovering coupled charge, spin, and phonon dynamics in magnetic materials by combining elemental selectivity with ultrafast time resolution in a tabletop source. In this talk, we address an important question in magneto-optics that has implications for understanding femtosecond magnetism: is the signal from the transverse magneto-optical Kerr effect at the M-shell absorption edges of a magnetic material purely magnetic or perturbed by non-magnetic optical artifacts? We conclusively show that high harmonics sensitively probe the magnetic state, with negligible contributions from electronic effects because of hot-electron dynamics. Finally, our measurements are in excellent agreement with conventional visible-wavelength magneto-optics probes and illustrate the power of high harmonics for probing the dynamics in magnetic materials.