Barium Ferrite Films Grown by Pulsed Laser Ablation

Perpendicular recording media with a high squareness in perpendicular M-H loop were developed by sputter-deposition. and their low noise property as well as high recording performances were confirmed The media with thicknesses of 30 to 200 nm were prepared on glass substrates by dc-magnetron sputtering using a Co-Crzo-Nb4 target Media of Co-Crz4 and Co-CrI8-Ta, were also prepared as the comparison A Ti underlayer was used to assist the c-axis orientation of hcp structure of the Co-Cr alloy films The substrate temperature was chosen for each CO-Cr alloy system so that the highest perpendicular coercivity was obtained A high perpendicular squareness, SQ , of around 0 7 were achieved for Co-Cr-Nb and CO-Cr-Ta films while that of less than 0 5 for Co-Cr films Medium noise, integrated for 0 to 200 kFRPI, were measured using a merged MR head It was found that the medium noise strongly related to the amount of demagnetization. Ms 6 (I-SQL) Therefore, the medium with higher SQL exhibited lower noise It was also found that reduction in noise with lowering the thickness for the three kinds of media was so large that thinner media resulted in higher signal to noise ratios, S/N, suggesting enhanced magnetic decoupling between the grains at the initial growth layers Although the change in noise with the thickness was steeper for both the Cc-Cr-Nb and CO-Cr-Ta media than Co-Cr media. the Co-Cr-Nb media exhibited lower noise than the Co-Cr-Ta media by 2-3 dB Thus the CO-Cr-Nb medium with 50 nm thickness exhibited the lowest noise It was suggested that Nb addition more favored nucro-segregation of Cr in the film and also magnetic coupling along the thickness than Ta An S/N of 37 dB for a track width of 2 7 k m with DSo of 140 kFRPI was obtained for the Co-Cr-Nb medium The medium noise was hardly dependent on recorded signal densities, indicating the charactenstic of pependicular recording media A higher recording resolution of over 250 kFFW of the medium was also confirmed by using a small gap MIG head Thermal stability of the media will be also discussed