Persistent magnetic coherence in magnets

The precessional motion of magnetization around the magnetic field decays on a damping time scale after which any information of the precession seems to be lost. This damping is a fundamental bottleneck for the use of magnets in information processing. Here we demonstrate the recall of the magnetization-precession phase after times that exceed the damping timescale by two orders of magnitude using dedicated two-colour microwave pump–probe experiments for an ittrium iron garnet (Y3Fe5O12) microstructured film. Time-resolved magnetization state tomography confirms the persistent magnetic coherence by revealing a double-exponential decay of magnetization correlation. We attribute persistent magnetic coherence to a feedback effect, that is, coherent coupling of the uniform precession with long-lived excitations at the minima of the spin-wave dispersion relation. Our finding liberates magnetic systems from the strong damping in nanostructures that has limited their use in coherent information storage and processing.