Oscillatory interlayer magnetic coupling of sputtered Fe/Nb superlattices

The saturation field of sputtered Fe/Nb superlattices oscillates as a function of the Nb thickness with a periodicity of ∼9 A. In contrast to the case of Fe/Cr superlattices, the concurrent magnetoresistance oscillations were found to be very weak. Yet polarized neutron reflection measurements confirm that the Fe/Nb superlattices with high saturation field possess a magnetic ground state of the +−+− type. Neutron and x‐ray measurements indicate that, while the crystalline and antiferromagnetic order is well developed along the thickness of the film, the average lateral size of the crystallites (as well as of the magnetic domains) is quite small. This effect (thought to be related to the gross mismatch of the iron and the niobium crystal lattices) may be the cause of the high overall resistance of the material, and its weak dependence on the magnetization.