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.