Deeply nonlinear magnon-photon hybrid excitation

TL;DR

This study explores how increasing microwave power induces nonlinear effects in magnon-photon coupling within a yttrium iron garnet hybrid system, revealing a power-dependent suppression of coupling due to magnetostatic mode dissipation.

Contribution

It demonstrates the power-dependent nonlinear suppression of magnon-photon coupling caused by Suhl's instability in a hybrid system at room temperature.

Findings

Strong coupling at low power evidenced by level repulsion.

Coupling suppression occurs above a certain power threshold.

Magnetostatic modes are destabilized by nonlinear spin-wave interactions.

Abstract

We investigate the microwave-power dependence of magnon-photon coupling in a yttrium iron garnet-sphere/split-ring-resonator hybrid system at room temperature and demonstrate that nonlinear spin-wave interactions suppress the coupling through power-induced dissipation of magnetostatic modes. At low microwave power, the modes exhibit pronounced level repulsion, evidencing strong coupling to the microwave field. As the power increases, however, magnon linewidth broadening progressively weakens the coupling and ultimately suppresses it entirely below a threshold external magnetic field. We show that this behavior originates from Suhl's first-order instability: magnetostatic modes, which couple to the resonator, parametrically excites two counter-propagating magnons at half its frequency, causing modes below the threshold external magnetic field to vanish. In contrast, magnon modes above the threshold field remain robust even at high power, as the instability criterion is not satisfied in that regime. These results reveal a well-defined nonlinear boundary for magnon-photon coupled systems and highlight a favorable regime for exploiting nonlinear magnonics for frequency conversion, switching, and other functional magnonic devices.