Sequentially evaporated thin film of Bi and Co-Ni with high coercive force

The magnetic properties and microstructures of films prepared by sequential evaporation of Bi and pure Co or Co-Ni alloys with up to 60 at.% Ni were investigated. The coercive force of the film rises rapidly with increasing substrate temperature above 100 °C and reaches a maximum at around 150-170°C. The composition of the Co-Ni alloy layer affects the coercive force, with 40 at.% Ni giving the best results. In the layered film of 300 Å thick Co60Ni40over 80 A thick Bi, the coercive force HC is 1000 Oe and the squareness ratio Mr/Ms exceeds 0.80. These properties are isotropic and can be adjusted by varying the thicknesses of the magnetic layer and the non-magnetic Bi layer. TEM observation shows that crystallites of the film have no preferred orientation. Examination by Auger Electron Spectroscopy reveals the diffusion of Bi atoms into the magnetic layer.