Effect of Thickness on Magnetic Properties and Microstructure of CoPt L1₁ Metastable Films

L1₁ CoPt thin films, a metastable phase with a rhombohedral unit cell, with different thickness t (from 2 nm to 100 nm) were sputtered on MgO(111) substrates at 350 °C. A high perpendicular magnetic anisotropy K _u over 2×10⁶ J/m³ and large anisotropy field H ^4K _K of about 2.4 MA/m at 4 K are found in the films with t ≥ 20 nm. Magnetic properties degrade with decreasing of t. Even so, a large anisotropy field at room temperature H ^RT _K of 1 MA/m is observed in the film with t = 2 nm. Microstructure results confirm that films retain continuous morphology and (111)-texture even for the thinnest case. Our results demonstrate that L1₁ CoPt films show great potential used for percolate recording media, a low-noise media comprising strongly exchange-coupled magnetic grains.