Optical control of RKKY coupling and perpendicular magnetic anisotropy in a synthetic antiferromagnet.

Synthetic antiferromagnetics (SAF) provide an excellent platform for antiferromagnetic spintronics. Recently, the voltage-control of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in SAFs was studied experimentally. Optical control would offer unique opportunities for the ultrafast manipulation of spin states, however, it has yet to be demonstrated. Here, using femtosecond laser excitations in a [Co/Pt]-based perpendicular magnetic anisotropy (PMA) synthetic antiferromagnet (p-SAF), we drive a reduction of the RKKY coupling and the PMA. We attribute the reduced RKKY interaction to the optically smeared Fermi wave vector of the Ru layer, which mediates the exchange coupling between the constituent ferromagnetic layers. The PMA exhibits the same amplitude of decrease as the RKKY coupling, which we associate with electron redistributions in the 3d orbitals caused by the optically smeared Fermi level. While the pump excitation process is shown to have an influence on the modulations, thermal contributions are excluded. Our study establishes a link between the RKKY coupling and the PMA in a p-SAF structure and provides an approach to tune them in parallel.