Indirect exchange coupling and spin polarization in Fe/AlFe/Fe trilayers

(Al/Fe)(n) superlattices were grown by the alternate deposition of n Al and Fe monolayers on a Fe (0 0 1) buffer layer on cleaved MgO (0 0 1) substrat es. LEED and GEMS measurements proved that (FeAl)-Fe-57 Ordered alloy (CsCl -type) was formed. The (AlFe)(n) monoatomic superlattices were then used as non-magnetic spacers in MgO (1 0 0)/Fe/(AlFe)(n)Al-1/Fe trilayers. The mag netic hyperfine field at the nuclei of a Fe-57 probe layer in the center of the nonmagnetic spacer, being a measure of the spin polarization from the ferromagnetic Fe layers, was investigated as the function of the total spac er thickness. A non-monotonous dependence of the polarization effect vs. th e spacer thickness was found. The magnetic hyperfine field data were correl ated with the MOKE measurements, which revealed a strong ferromagnetic coup ling between the Fe layers. (C) 1999 Elsevier Science B.V. All rights reser ved.