Interaction of superconductivity and itinerant-electron magnetism: Critical fields of Ni/V superlattices

We present experimental results showing an anomalous behavior in the critical fields of superconductor/magnet superlattices. Close to the superconducting transition temperature the critical-field anisotropy is reversed (i.e., the parallel critical field is smaller than the perpendicular critical field). As the temperature is reduced the anisotropy reverts to the normal behavior. This effect is attributed to the competing interaction between the itinerant magnetism in the magnetic (Ni) layer and the superconducting (V) layers.