All-optical detection and evaluation of magnetic damping in synthetic antiferromagnet

Abstract

Synthetic antiferromagnets (SyAFs), which consist of a thin nonmagnetic spacer sandwiched by two nanolayer ferromagnets with antiferromagnetic coupling, are promising artificial magnets for spintronic memory and have attracted attention for use in future ultrafast spintronics devices. Here, we report an observation of the magnetization dynamics in a SyAF with nearly antiparallel magnetizations using an all-optical pump-probe technique. High- and low-frequency precessional dynamics of the SyAF were clearly observed. The damping of both modes was explained theoretically in terms of the dynamic exchange coupling induced by the spin current.