Film Structure Dependence of Demagnetization Time Scale of RE-TM GdFeCo Alloy Thin Films

Abstract

In conventional magneto-optical (MO) recording which triggered with nanoseconds pulsed laser irradiation, the time scale of heat-up and cool-down process depends on thermal diffusion property in multilayered recording media. The speed limits of heating and cooling process are important issue for fast heat assisted magnetic recording. Femtosecond pulsed laser light allow excitation of magnetic systems much shorter than the time scale of thermal diffusion. In this study, we investigated the film structure dependence of ultrashort laser-induced demagnetization of 20 nm thick GdFeCo alloy films, under the variety of with / without intermediate dielectric layer and heat sink layer. After the laser excitation, we found two time region from magnetic behavior: rapid step-like reducing process of magnetization and following recovering process with precessional motion. The time scale of first rapid step-like demagnetization processes is conformed as within picoseconds range for all the cases.