Ultrafast spin manipulation in ferrimagnetic GdFeCo by femtosecond pulsed laser

摘要

Femtosecond pulsed laser light allow excitation of magnetic systems much shorter than the time scale of thermal diffusion represented by conventional Fourier's law. In this time scale, heating and demagnetization phenomena arise via novel, strongly non-equilibrium non-adiabatic way, and cannot be explained by conventional equilibrium thermo dynamics description. For further progress in information technology, understanding spin dynamics in magnetic materials is an issue of crucial importance. Ultrafast laser excitation of itinerant ferromagnets as Co, Ni, or Fe leads to a demagnetization on the femtosecond time scale, little is known about rare-earth magnet such as Gd. In Gd, the optically excited electrons of the 5d6s band carries only 9% of the total moment while the localized 4f electrons dominate the magnetic spin moment. How and how fast the magnetic moments in ferrimagnetic alloy system consists of Gd and FeCo sublattices are excited, with photon energies in the visible range?