We demonstrate the long range strong coupling of magnetostatic modes in spatially separated ferromagnets mediated by a microwave frequency cavity. Two spheres of yttrium iron garnet are embedded in the cavity and their magnetostatic modes probed using a dispersive measurement technique. We find they are strongly coupled to each other even when detuned from the cavity modes. We investigate the dependence of the magnet-magnet coupling on the cavity detuning Δ, and find a 1/Δ dependence also characteristic of cavity-coupled superconducting qubits. Dark states of the coupled magnetostatic modes of the system are observed, and ascribed to mismatches between the symmetries of the modes and the drive field.
@article{arxiv.1506.06049,
title = {Cavity mediated coherent coupling of magnetic moments},
author = {N. J. Lambert and J. A. Haigh and S. Langenfeld and A. C. Doherty and A. J. Ferguson},
journal= {arXiv preprint arXiv:1506.06049},
year = {2016}
}