Magnetostatic mode excitations in ferromagnetic layer compounds

Abstract

Recent experiments with excited magnetostatic modes in ferromagnetic layer compounds will be reviewed. Natural platelets of the layer compounds (C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2n+1</inf> NH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> CuCl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> exhibited 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 H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</inf> and M <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</inf> known 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' <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</inf> . Both groups show foldover effects at higher power levels.