Magnetic properties of finite antiferromagnetic superlattices: Statics, dynamics, and the surface spin-flop phase

We use the numerical self-consistent mean-field method to examine the ground-state configurations of finite-size multilayers constructed from ferromagnetic films which are antiferromagetically coupled. At intermediate fields, a surface spin-flop state, as suggested by Keffer and Chow, has been found for even numbered multilayers, but not for odd numbered ones. These are confirmed by experimental observations on systems such as Fe/Cr. A simple macroscopic approach has been devised in calculating the spin-wave excitations for the various field-induced ground states. Special emphasis is placed on the influence of interfilm dipolar couplings on the spin-wave spectrum. We note, for example, that there are substantial differences for the two cases ${\mathit{k}}_{\mathrm{\parallel }}$D≪1 and ${\mathit{k}}_{\mathrm{\parallel }}$D≳1, with D the thickness of the finite superlattice, and ${\mathit{k}}_{\mathrm{\parallel }}$ the wave vector of the spin waves parallel to its surface.