Spin Waves in Antiferromagnetically Coupled Multilayers

Abstract

We investigate how the static and dynamical magnetic properties of Fe/Cr finite superlattices with antiferromagnetic coupling depend on the ratio between the uniaxial anisotropy constant and the interlayer exchange constant of Fe films. The spin waves are calculated by considering dipole interaction, intralayer and interlayer exchange coupling, uniaxial anisotropy, in presence of an external field. The calculated spectra are compared with recent experimental Brillouin scattering data which exhibit two spin waves peaks.PACS numbers: 75.30.Pd, 75.70.Cn In the last ten years ferromagnetic/nonmagnetic multilayers have attracted great interest mainly because of the antiferromagnetic interlayer coupling and the giant magnetoresistance effect. In particular, these effects have been studied in Fe/Cr systems of different type [1][2][3]. From the theoretical point of view, several investigations have been devoted to the study of the static and dynamical magnetic properties of antiferromagnetically coupled multilayers with a finite even numbers N of ferromagnetic layers [4][5][6][7].Within the mean field approach proposed by Mills [8], and lately adopted by several authors [9,[4][5][6][7], the energy of N magnetic layers in an applied magnetic field Ho is given by (in magnetic-field units):where 1 is the layer index and HE and HA (both positive) are the effective interlayer exchange coupling and the uniaxial anisotropy constant, respectively. The angle αl between the magnetization of the l-th layer and the external field Ho is positive for clockwise rotation with 1 odd and negative with 1 even. Both Ho and the magnetization are assumed to be parallel to the surfaces of the layers. As a result of the three competing energy terms in Eq. (1), four magnetic phases exist, depending on the value of Ho [4][5][6][7]:(i) for low field8 (Ho < Hs ) the system is antiferromagnetically aligned;