A comparative study on the PMA behavior of 5-nm thick Co49Pt51 films grown at room temperature and at high temperature on glass substrates

Co49Pt51 alloy films with strong perpendicular magnetic anisotropy (PMA) have been most often grown on either single crystal or glass substrates with deposition temperature of about 350 °C using Pt/Ru as an underlayer. In contrast, in this study, 5-nm thick Co49Pt51 alloy films with significant PMA were fabricated on glass substrates at room temperature (RT) using a combination of Ta and Pt underlayers. The structural and magnetic properties of the Co49Pt51 films obtained at RT (RT-CoPt) were compared with that of those produced by the conventional high-temperature route (HT-CoPt). The x-ray diffraction studies showed the evolution of highly textured Pt (111) peak accompanied by a CoPt (222) shoulder for the RT-CoPt films, similar to that of the HT-CoPt films. The microstructural studies revealed extremely smooth surface with root mean square roughness (Rrms) of 0.5 nm for the RT-CoPt films, while the HT-CoPt films showed wavy surface with Rrms of 2.4 nm. The out-of-plane and in-plane hysteresis loops demonstrated the existence of strong PMA for both the RT-CoPt and HT-CoPt films. The estimated magnetic parameters for the RT-CoPt films such as squarness ratio, SQR (0.96), perpendicular coercivity, Hc⊥ (822 Oe) and magneto-crystalline anisotropy constant, Ku (6.4×106 erg/cm3) was found to be comparable to that of those obtained with the HT-CoPt films (SQR=0.96, Hc⊥=1810 Oe and Ku=7.1×106 erg/cm3). - Highlights: • 5-nm thick Co49Pt51 films with strong PMA were grown at RT using Ta/Pt underlayers. • Relatively smooth surface (Rrms=0.5 nm) was achieved for the RT-Co49Pt51 films. • Performance of RT-Co49Pt51 was superseding with the conventionally processed one. • High Ku (6.4×106 erg/cm3), high SQR (0.96) and moderate Hc⊥ (822 Oe) were achieved. • The role of Ta and Pt layers for the underlying PMA was investigated using MFM