Interplay between superconductivity and ferromagnetism in epitaxial Nb(110)/Au(111)/Fe(110) trilayers

摘要

In order to clarify the influence of ferromagnetism on superconductivity through a normal-metal layer, the superconducting properties of epitaxial Nb(110)/Au(111)/Fe(110) trilayers were studied as a function of the thickness t_(Au) of the intervening Au layer. Structural characterization of the samples revealed sharp interfaces, almost free from roughness. A strong suppression of the superconducting transition temperature T_c was observed for t_(Au) < 10 A, implying a strong spin polarization of the Au layer in the vicinity of the Au/Fe interface. A periodic change of T_c with a period of ～21 A (～nine atomic monolayers of Au) was observed for 20 < t_(Au) < 104 A. Neither the Fermi surface nesting of the normal-metal layer nor Fulde-Ferrel-Larkin-Ovchinnikov oscillations induced by a superconducting proximity effect in the ferromagnet can by themselves account for the observed period. These results suggest that a more subtle form of quantum interference occurs in very clean trilayer systems.