High coercivity of CoCrTa on a very thin Cr underlayer

RF sputtered CoCrTa films (Co-15 wt.% Cr-4.7 wt.% Ta) deposited on various thicknesses of Cr underlayer (200 AA to 800 AA) for longitudinal magnetic recording were investigated. A coercivity of 1500 Oe can be easily obtained on a 200-AA Cr underlayer with low argon pressure (4 mtorr) and high substrate bias (-100 V). Emphasis has been placed on the influence of (1010) texture formation on the in-plane coercivity. Microstructure observation revealed by TEM shows that the grain size and grain structure were changed with the thickness of the Cr underlayer. Several mechanisms are proposed to explain the experimentally observed phenomena of argon pressure and substrate bias effects on the coercivity change of this CoCrTa/Cr film.>