Lawrence Berkeley National Laboratory

Nickel-platinum-based synthetic ferrimagnets (SFi's) are highly tunable and rare-earth-free materials that allow ultrafast all optical control of magnetism to be explored. This study considers a SFi composed of a ferromagnetic [Ni/Pt] multilayer and a ferromagnetic Co layer, separated by an Ir layer that mediates an antiferromagnetic coupling. Helicity-independent all optical switching (HI-AOS) between two antiparallel magnetization states is observed. AOS may be realized at increased temperature through reduction of the thickness of the Pt layers. Switching is unidirectional and has a strong dependence on the applied magnetic field history, which suggests the possible presence of a nanoscale magnetic texture that may be important in controlling AOS in SFi systems.