Formation of rhombohedral L11 CoPt thin film on glass and MgO(111) substrate

●Rhombohedral CoPt superstructure film with strong perpendicular magnetic anisotropy.●Enhanced coercivity in L11 CoPt thin films with glass substrates.●Continuous morphology and large Ku in L11 CoPt thin films with reduced thickness.●Multiple impedances of domain wall motion adjusted the coercivity.

L11 type CoPt superstructure, a rhombohedral meta-stable phase, thin films with different thickness (t) were sputtered on glass, Pt/glass, and MgO(111) substrates. Perpendicular magnetic anisotropy (PMA) is obtained as the CoPt films, which are deposited on Pt(111)/glass and MgO substrates. The coercivity (Hc) of CoPt/Pt/glass is higher than that of CoPt/MgO(111) film due to the smaller lattice misfit at CoPt/Pt interface and domain wall impedance at CoPt grain boundary. For the CoPt/Pt/glass and CoPt/MgO films, Hc usually increases with reducing the t from 50 nm to 5 nm. This result could be attributed to the roughness effect at CoPt/Pt and CoPt/MgO interfaces. Without Pt underlayer, CoPt thin film exhibits soft magnetic phase on glass substrate. In this study, higher Hc of about 141 kA/m is shown on 3 nm-thick CoPt film on Pt/glass. The improvement of perpendicular magnetic properties are obtained by replacing the MgO(111) with Pt/glass, inducing high potential of L11 CoPt in future applications.