High perpendicular magnetic anisotropy of CoPtCr/Ru films for granular-type perpendicular media

The perpendicular magnetic anisotropy K_u of CoPtCr films deposited on Ru seed layers is discussed as a function of film composition. Moreover, the change in K_u by the addition of SiO₂ is examined in light of thermal stability of CoPtCr-SiO₂ media. The K_u of Co-10 at % Cr shows a high value of ∼5×10⁶ erg/cm³, which is much higher than that reported by Bolzoni et al. The addition of Pt to the Co-10 at % Cr film results in a further enhancement of K_u. A maximum K_u of nearly 10×10⁶ erg/cm³ is observed at 25∼30 at % Pt. All series of films with various Cr contents show maximum values of K_u at 25∼30 at % Pt. The maximum value for CoPt (Cr=0) films reaches ∼15×10⁶ erg/cm³. The value of magnetocrystalline anisotropy of grains K_u^g, calculated by taking account of the volume fraction of CoPtCr grains, decreases as the SiO₂ content increases. However, the K_u^g maintains a large value of more than 7×10⁶ erg/cm³, even at 10 at % SiO₂ in addition to (Co₉₀Cr₁₀)₈₀Pt₂₀, which indicates a high potential of CoPtCr-SiO₂ media to resist thermal agitation of magnetization.