Surface retarded modes of magnetic superlattices with antiferromagnetic coupling

We calculate retarded modes of lateral magnetic superlattices with antiferromagnetic interlayer coupling, which are described with an effective medium theory. There can be two magnetic orderings in these superlattices; the flop spin and parallel spin orderings in an external magnetic field normal to magnetic or nonmagnetic layers. We find that in the Voigt geometry the frequency of surface modes versus the external magnetic field and the interlayer coupling is very different in these two different magnetic orderings. The mode frequency, in the first ordering, is rather sensitive to the interlayer coupling. We also find two critical values of the external field for the presence of the surface mode.