Magnetic circular x-ray dichroism (MCXD) measurements at the Co $L_{2,3}$ and $M_{2,3}$ core edges reveal a strongly enhanced perpendicular Co orbital moment ( $m_{\mathrm{orb}}$) in Co/Pt multilayers which show perpendicular magnetic anisotropy (PMA). MCXD signals at the Pt $N_{6,7}$ and $O_{2,3}$ edges, arising from Pt $5d-\mathrm{Co}3d$ hybridization, persist for the thinnest Co layer. The hybridization is shown to be localized at the Co/Pt interface and to cause the $m_{\mathrm{orb}}$ enhancement which drives PMA. Unambiguous evidence for a transition from fcc to hcp Co is presented and $m_{\mathrm{orb}}$ of bulk fcc Co has been determined to be $0.11{\mu }_B$ for the first time.

• Received 13 November 1997

DOI:https://doi.org/10.1103/PhysRevLett.81.5229