The effect of symmetry on the resonance spectra of antiferromagnetically coupled oscillators has attracted new interest with the discovery of symmetry-breaking induced anticrossings. Here, we experimentally characterize the resonance spectrum of a synthetic antiferromagnet Pt/CoFeB/Ru/CoFeB/Pt, where we are able to independently tune the effective magnetization of the two coupled magnets. To model our results, we apply the mathematical methods of group theory to the solutions of the Landau-Lifshitz-Gilbert equation. This general approach, usually applied to quantum-mechanical systems, allows us to identify the main features of the resonance spectrum in terms of symmetry breaking and to make a direct comparison with crystal antiferromagnets.

• Received 23 September 2020
• Revised 9 February 2022
• Accepted 14 March 2022

DOI:https://doi.org/10.1103/PhysRevB.105.104436