Fe/Cu/Fe and Co/Cu/Co multilayers on Cu(111): the absence of oscillatory antiferromagnetic coupling

The magnetooptical Kerr effect was used to search for evidence of the oscillatory antiferromagnetic (AF) coupling associated with the recently discovered giant magnetoresistance effect (GMR) in Fe/Cu/Fe and Co/Cu/Co multilayers. The GMR effect was reported in samples grown by magnetron sputtering methods on Si wafers. In the present work the multilayers are grown by molecular beam epitaxy (MBE) techniques on Cu(111) single-crystal substrates. None of the resulting multilayers showed any evidence of the oscillatory AF coupling being sought. It is concluded that (111)-oriented crystallites in the sputtered multilayers make little if any contribution to the observed oscillatory AF coupling. However, oscillatory AF coupling does not occur in MBE-grown multilayers on Cu(100), and its dependence on Cu thickness is remarkably similar to that of the sputter-deposited multilayers. This suggests that (100)-oriented grains in the sputter-deposited multilayers may be partly, or perhaps even largely, responsible for the AF coupling. Supporting this suggestion are preliminary X-ray diffraction pole-figure measurements made on three of the sputter-deposited multilayers which indicate that the tendency to (111) texture is not extremely strong, and that other crystalline grains are present