Enhance the coercivity of the rhombohedral lattice L1_1 CoPt thin film on glass substrate

摘要

CoPt L1_1 thin films with different thicknesses of 2-50 nm were epitaxially grown on Pt(111) underlayer on amorphous glass substrates by magnetron sputtering. The results show that high out-of-plane coercivity (H_(c⊥)), good perpendicular magnetic anisotropy (PMA), large magnetocrystalline anisotropy constant (K_u), and negative nucleation field (H_n) were achieved simultaneously in the thinner CoPt films, indicating a high impedance in the domain wall motion. TEM cross-section images displayed a well developed epitaxy of CoPt L1_1(111) orientation starting from Pt(111) plane and extending into magnetic CoPt(111) film, inducing the PMA of CoPt films. Surface morphologies of CoPt/Pt/glass films confirmed that surface CoPt grain sizes are similar to their magnetic domain sizes found in magnetic force microscopy results, evidencing the grain boundary pinning effect on the enhancement of H_(c⊥). When the thickness of CoPt film was reduced to 3 nm, higher PMA with H_(c⊥) ～ 1.8 kOe and K_u ～ 1.9 × 10~7 erg/cm~3 suggests that L1_1 CoPt thin film is a promising candidate in the design of advanced spintronic devices, magnetic sensors, and magnetic recording media.