Enhanced Coercivity in L11 CoPt Thin Film on Glass Substrate by Fine-Tuning Pt Underlayer

Perpendicularly magnetized CoPt films with L1(1) rhombohedral lattice were deposited on glass substrates with a Pt underlayer. The results show that the magnetic properties of CoPt films are substantially affected by post-annealing time (t(a)) and temperature (T-a) of Pt underlayer, as well as the thickness of Pt underlayer (t(Pt)). Soft magnetic phase is formed as CoPt is directly deposited on the glass substrate at 350 degrees C. Besides, a very low coercivity (H-c) of 103 kA/m is obtained when t(a), T-a, and t(Pt) are 5 min, 300 degrees C, and 20 nm, respectively. Further varying t(a), T-a, and t(Pt) to 15 min, 350 degrees C, and 25 nm increases H-c to about 207 kA/m. The microstructural studies indicate that the size of CoPt grain is the key factor to determine the magnetic properties, which could be controlled by the formation conditions of Pt underlayer. In this study, the optimum deposition conditions for Pt underlayer to obtain L1(1) CoPt phase with high H-c are t(a) = 15 min, T-a = 350 degrees C, and t(Pt) = 20-25 nm. Our study demonstrates that using a Pt underlayer/glass substrate can effectively replace the single-crystal substrate and also enhance H-c of CoPt film, which may increase the application potential of L1(1) CoPt film in the future.