High coercivity FeSmN thin films for longitudinal magnetic recording media

FeSm thin films with an Fe/Sm atomic ratio of 9.2 have been deposited by dc magnetron sputtering on Ta and Cu substrates held at 400°C. FeSmN films with in-plane easy axes were obtained by annealing the FeSm films in-situ under a nitrogen atmosphere of 300 Torr at a temperature of 400°C. The coercivity of the FeSmN films varies from 2 kOe to as high as 7 kOe depending on the deposition conditions. Typical FeSmN films have a magnetization of ~140 emu/g, a squareness of 0.90 and a coercivity squareness of 0.75. It was found that when a Cr underlayer was deposited at a substrate temperature of 350°C, FeSmN films of 150 nm thickness with an in-plane coercivity of 6.4 kOe, a squareness of 0.90 and a coercivity squareness of 0.6 were obtained