Magnetic superlattices composed of ferromagnetic films (Fe and Gd) which couple antiferromagnetically at the interfaces are studied. In a magnetic field a variety of different spin configurations are possible. We show how these phases are reflected in magnetization and susceptibility measurements. In particular, a twisted spin configuration is characterized by a much larger susceptibility than an aligned spin configuration. We show that small changes in the layering pattern can lead to large changes in $M\left(T\right)\mathrm{}$ and static susceptibility. In contrast, changes in the value of the interface exchange parameter cause large changes only in the weak-coupling limit.

• Received 3 October 1988

DOI:https://doi.org/10.1103/PhysRevB.39.12316