Magnetostatic mode excitations in ferromagnetic layer compounds

Recent experiments with excited magnetostatic modes in ferromagnetic layer compounds will be reviewed. Natural platelets of the layer compounds (CnH2n+1NH3)2CuCl4exhibited up to 75 well resolved magnetostatic modes. These compounds are quasi 2-dimensional magnets with strong ferromagnetic interaction inside the layers and weak ferromagnetic (n = 1) or antiferromagnetic interaction (n > 1) between the layers. The spectra have been calculated assuming the permeabilities of a continuum with easy-plane anisotropy and uniaxial g-tensor. For thin platelets, theory and experiments agree with parameters HAand Moknown from other methods. In addition to the forementioned modes, a second group of magnetostatic modes has been observed at higher field values in these compounds with antiferromagnetic interlayer interaction (n = 2,3). There is evidence that these weak lines are excitations of the antiferromagnetic mode in the collapsed spin state. This group allows the determination of the interlayer exchange field H'E. Both groups show foldover effects at higher power levels.