2002 Volume 26 Issue 4 Pages 453-456
Barium ferrite thin films with lanthanum ions and cobalt ions substituted for barium ions and iron ions were prepared by the conventional sputtering method. To crystallize a hexagonal barium ferrite phase, the as-deposited films were annealed at a temperature of 900°C for 5 hours in air. The crystal orientation of La-Co substituted barium ferrite thin films was changed by controlling their compositions. The c-axis direction of the hexagonal structure was changed from perpendicular to parallel to the film surface by increasing the Co concentration. An attempt was also made to reduce the film thickness of La-Co-substituted barium ferrite thin films, in order to utilize them as perpendicular magnetic recording media. However, when the thickness of the films was decreased, the coercivity of the films also decreased because of their poor crystallinity. It was considered that the poor crystallinity was caused by the diffusion of barium ions into substrates. Therefore, a Ba-rich buffer layer was used to prevent the loss of barium ions. The La-Co-substituted barium ferrite thin films with a Ba-rich buffer layer had good crystallinity at a film thickness of 20 nm, and their magnetizations were larger than those of single-layer barium ferrite thin films.
