Measuring the Magnon-Photon Coupling in Shaped Ferromagnets: Tuning of the Resonance Frequency

Abstract

Cavity photons and ferromagnetic spin excitations can exchange information coherently in hybrid architectures, at speeds set by their mutual coupling strength. Speed enhancement is usually achieved by optimizing the geometry of the electromagnetic cavity. Here we show that the geometry of the ferromagnet also plays a role, by setting the fundamental frequency of the magnonic resonator. Using focused ion-beam patterning, we vary the aspect ratio of different Permalloy samples reaching operation frequencies above 10 GHz while working at low external magnetic fields. Additionally, we perform broadband ferromagnetic resonance measurements and cavity experiments that demonstrate that the light-matter coupling strength can be estimated using either open transmission lines or resonant cavities, yielding very good agreement. Finally, we describe a simple theoretical framework based on electromagnetic and micromagnetic simulations that successfully accounts for the experimental results. This approach can be used to design hybrid quantum systems exploiting magnetostatic mode excited in ferromagnets of arbitrary size and shape and to tune their operation conditions.

Scanning Spin Probe Based on Magnonic Vortex Quantum Cavities

“…In this case, the width of the vortex resonance γ v will be enlarged if enough paramagnetic spins on the surface of the nanodisc satisfy the resonance condition. The line width γ v can be experimentally measured using superconducting microcircuits that can be optimally coupled to magnonic resonators. ,− In this way, the target spins can be deposited in powder or crystal form or from solution on the surface of the disc for nanoscopic EPR imaging.…”

“…The line width γ v can be experimentally measured using superconducting microcircuits that can be optimally coupled to magnonic resonators. 57 , 65 − 72 In this way, the target spins can be deposited in powder or crystal form or from solution on the surface of the disc for nanoscopic EPR imaging.…”