Magnetic behavior of superconductor/ferromagnet superlattices

A study of the electromagnetic response of superconductor/ferromagnet Nb/Co superlattices is presented. The dc magnetization is measured as a function of Co layer thickness, applied field H-a, and temperature. For very thin Co layers, no ferromagnetism is detected and the observed response is essentially that of a collection of uncoupled Nb layers. When the Co layer is thick enough for ferromagnetism to be established, prior to the field-cooled magnetization measurements, the Co layers are magnetically saturated in the parallel or antiparallel directions to H-a. In this case, the magnetic response of the otherwise uncoupled Nb layers is found to depend on both H-a and the stray fields.