Longitudinal evolution of magnetization of ferromagnets following ultrafast demagnetization: Role of finite size and shape of demagnetized region

摘要

A dependence of a relaxation rate on the shape of the demagnetized region fora longitudinal evolution of total magnetization to its equilibrium valuefollowing the ultrafast demagnetization is demonstrated. This shape-dependenceis caused by a motion of the wave front inside the demagnetized region. Thecontribution of the wave front for spherically symmetric shape of thedemagnetized region is up to 3 times and for cylindrically symmetric shape upto 2 times stronger than for one dimensional demagnetized region. This effectcan be observed after the demagnetization by a tightly focused femtosecondlaser pulse.