Fig. 1: Magnon radiative damping controlled by LDOS (local density of photon states).

a Experimental setup of the coupled magnon–photon system in a circular waveguide cavity. b Transmission coefficient \(| {S}_{21}|\) from measurement (circles) and simulation (solid lines), with insets showing normalized LDOS distribution for standing-wave resonance at 12.14 GHz and continuous wave at 11.64 GHz. The color bar shows the scale for normalized LDOS with arbitrary unit. c By coupling the magnon mode with photon mode in a waveguide cavity, the radiative damping of a magnon can be the dominant energy dissipation channel compared to its intrinsic damping. d Measured amplitude of the transmission coefficient \(| {S}_{21}|\) as a function of the bias magnetic field. Anti-crossing dispersion can be clearly observed for coupled magnon–photon states. The squared amplitudes of the transmission coefficients (\(| {S}_{21}(H){| }^{2}\)) are shown at fixed frequencies of 11.64 GHz (e), 12.14 GHz (f), and 12.64 GHz (g), with the x-axis offset \({H}_{\mathrm{m}}\) being the biased static magnetic field at magnon resonance. The squares represent the measured \(| {S}_{21}(H){| }^{2}\) spectra, and the solid line from the lineshape fit represents the reproduced experimental results. In this figure, experimental errors are smaller than the symbol sizes.