Observation of Magnon Density of States in K₂CuF₄ by Subthreshold Parallel Pumping

Abstract

Subthreshold steady-state absorption under parallel pumping in a quasi-two-dimensional ferromagnet K₂CuF₄ has been observed at a pumping frequency of 8.9 GHz in the temperature range from 1.4 to 4.2 K. The magnon density of states by which the magnitude of the absorption is mainly determined is experimentally revealed near the band edge including the singular point due to weak interlayer exchange interaction. A prospect for parallel pumping in a quasi-one-dimensional ferromagnet is given.