Effect of Ag under-layer on patterning of periodic magnetic structure using femtosecond laser-induced crystallization

Abstract

Femtosecond laser-interference crystallization (FLIC) was used to form a spatially periodic magnetic structure by selectively crystallizing a paramagnetic amorphous Co 2MnSi thin film, which was covered with an Ag thin film. Depending on the incident beam direction, presence of the Ag capping layer improved FLIC of a-Co 2MnSi by accentuating the structural difference between dark and bright band regions. Although the crystalline region remained unchanged with or without insertion of the Ag film, crystallization of the dark band region was reduced by the Ag film. The dark band region was in a microcrystalline state, containing a non-equilibrium solid solution of Co, Mn and Si. During FLIC, the Ag film acted as a heat sink, efficiently absorbing the energy released by the crystallization of amorphous Co 2MnSi thin film, thus sharpening lateral thermal gradient producing FLIC and help confining the laser energy to the bright band region.