Laser-induced ultrafast demagnetization and perpendicular magnetic anisotropy reduction in a Co$_{88}$Tb$_{12}$ thin film with stripe domains

Abstract

We use time-resolved x-ray resonant magnetic scattering (tr-XRMS) at the Co M2,3-and Tb O1edges to study ultrafast demagnetization in an amorphous Co88Tb12 alloy with stripe domains. Combining the femtosecond temporal with nanometer spatial resolution of our experiment, we demonstrate that the equilibrium spin texture of the thin film remains unaltered by the optical pump-pulse on ultrashort timescales (<1 ps). However, after 4 ps, we observe the onset of a significant domain wall broadening, which we attribute to a reduction of the uniaxial magnetic anisotropy of the system, due to energy transfer to the lattice. Static temperature dependent magnetometry measurements combined with analytical modeling of the magnetic structure of the thin film corroborate this interpretation.

Ultrafast high-harmonic nanoscopy of magnetization dynamics

“…Despite the high spatiotemporal resolution of the approach, up to now, we have not found unambiguous evidence for a significant softening of domain walls as may have been expected from the characteristics of superdiffusive spin currents and previous diffraction experiments [3,11,[53][54][55][56][57]. Several reasons may account for this observation.…”