Fig. 4: Parameter fitting of coherent oscillation.

a Experimentally obtained temporal evolution of \(| {\tilde{F}}_{{{{{{{{\bf{k}}}}}}}}}(t){| }^{2}\) at B = 11.5 mT. b Calculated temporal evolution of magnon amplitude \(| {\tilde{a}}_{{{{{{{{\rm{k}}}}}}}}}(t){| }^{2}\). c Temporal evolution of \(| {\tilde{F}}_{{{{{{{{\bf{k}}}}}}}}}(t){| }^{2}\) at different wavenumbers. Gray curves represents fitting curves according to Eq. (3). Errors of the data are evaluated as a standard deviation, which is smaller than the data plot.