Co/Cu multilayers studied by using the119Sn probe

To observe spin polarization in nonmagnetic layers sandwiched by magnetic layers,¹¹⁹Sn Mössbauer spectra of Co(20 Å)/Cu(20-x Å)/¹¹⁹Sn(1.5 Å)/Cu(x Å)] (x=0, 5 and 10) multilayers were measured. A magnetic fraction is observed in every spectrum, and the average hyperfine field ¯H _f at Sn nuclei in a Cu layer changes from 14 kOe (x=0) to 8 kOe (x=10). It was also observed that the polarization is greatly reduced by adding a Cr layer of only 2 Å to the Co/Cu interfaces. The spectrum of thex=10 film, measured under an external field of 30 kOe, cannot be interpreted without assuming magnetic fractions both in parallel and antiparallel to the external field, which indicates an oscillation of spin polarization in a Cu layer.