Enhanced Coercivity in $L1_{1}$ CoPt Thin Film on Glass Substrate by Fine-Tuning Pt Underlayer

Abstract

Perpendicularly magnetized CoPt films with L11 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 (ta) and temperature (Ta) of Pt underlayer, as well as the thickness of Pt underlayer (tPt). Soft magnetic phase is formed as CoPt is directly deposited on the glass substrate at 350 °C. Besides, a very low coercivity (Hc) of 103 kA/m is obtained when ta, Ta, and tPt are 5 min, 300 °C, and 20 nm, respectively. Further varying ta, Ta, and tPt to 15 min, 350 °C, and 25 nm increases Hc 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 L11 CoPt phase with high Hc are ta = 15 min, Ta = 350 °C, and tPt = 20-25 nm. Our study demonstrates that using a Pt underlayer/glass substrate can effectively replace the single-crystal substrate and also enhance Hc of CoPt film, which may increase the application potential of L11 CoPt film in the future.