Spin Wave Resonance in Perpendicularly Magnetized Synthetic Antiferromagnets

We report antiferromagnetic spin wave resonance in perpendicularly magnetized synthetic antiferromagnets consisting of Co/Ni multilayers and a thin Ru spacer layer. Two resonance modes were observed in the finite range of the out-of-plane bias magnetic field, where two magnetic moments separated by the Ru layer were antiferromagnetically aligned. These two modes show an opposite dependence on the bias magnetic field and correspond to right- and left-handed polarized spin waves. We also theoretically derive the spin wave dispersion for the perpendicularly magnetized synthetic antiferromagnets on the basis of an equation of motion. Our experimental results show good agreement with the theoretical analysis.