Magnetic and structural properties of L1₁ type CoPt-C ordered alloy perpendicular films as a function of C content

Magnetic and structural properties of L1₁ type (Co _0.5Pt_0.5)_100-X-C_X ordered alloy perpendicular films, fabricated on 2.5 inch size glass disks by sputter deposition, were examined as a function of C content, X. L1₁ type Co_0.5Pt_0.5-C polycrystalline films (10 nm thickness), with <111> axis (the easy axis) perpendicular to the film plane, were successfully fabricated even for a 30 vol% C content. Structural analysis indicated the segregation of C to the grain boundaries. Uniaxial magnetic anisotropy, K_u, of Co_0.5Pt_0.5 films without C addition was relatively low, about 1.5x10⁷ erg/cm³ under the present deposition conditions. However, the addition of 5 vol.% C to Co-Pt films enhanced the ordering, resulting in an increase in K_u to around 2.5 x10⁷ erg/cm³. A further increase in C content reduced K_u; however, K_u maintained a relatively large value of about 1.8x10⁷ erg/cm³ even for a 20vol% C content, without degrading the easy axis orientation perpendicular to the film plane. Experimental results demonstrated the potential of the L1₁ type Co_0.5Pt_0.5-C films for use in granular media applications, due to their very high K_u, the relatively low fabrication temperature, and good controllability of the grain orientation.