Effect of underlayer (Pt, Ru, Au, Ag) on L11 ordering in sputtered CoPt thin films

CoPt films without and with underlayers of Pt, Ru, Ag or Au were deposited on MgO(1 1 1) substrates by magnetron sputtering at 350 °C. Using a Pt underlayer resulted in an epitaxially grown Ll1 structure with enhanced chemical ordering, a high perpendicular anisotropy energy of 2.1 × 106 J m–3, and an anisotropy field of 2.4 MA m−1 at 4 K, which reduces the Ll1 ordering temperature to under 200 °C and produces a room-temperature anisotropy field that exceeds 1.6 MA m−1, indicating potential application for magnetic recording.