Ferromagnetic resonance determination of fcc→hcp structural change in epitaxial Co/Mn superlattices

A series of epitaxial [Co24 ÅMntMn]12 superlattices (3.2 Å≤tMn≤32 Å) was grown on hcp(0001) Ru buffer layers by ultrahigh vacuum e-beam evaporation. Ferromagnetic resonance has shown that for samples with 3.2 Å≤tMn≤12 Å, the cobalt layers are predominantly fcc and almost perfectly fcc for the sample having the thinnest Mn thickness [Co24 Å/Mn3.2 Å]12. For samples with greater Mn thickness (tMn≳12 Å), the cobalt layers are predominantly hcp with structural defects corresponding either to large inclusions of fcc Co or stacking faults.