Ferromagnetic resonance in K2CuF4 by means of quasi-optical methods in the millimeter wave range

We have studied ferromagnetic resonance in the millimeter wave range between 35 and 100 GHz with external fields ranging from 1 to 4 T. The results show that it is advantageous to employ quasi-optical methods in this range. Moreover, our results demonstrate also that propagation and polariton effects cannot be neglected in analyzing the spectra. The experiments have been performed on K₂CuF₄, a transparent quasi-two-dimensional ferromagnet.