A barium ferrite layer with low-Ba content was used as an underlayer f
or a high-Ba content barium ferrite thin film During the post-depositi
on annealing, the underlayer which has a lower nucleation rate than th
e top layer prevented grains from nucleating in the interdiffused regi
on at the interface with the substrate. As a result, the magnetic prop
erties were dramaticallyimproved as indicated by much higher coercivit
y squareness S and narrower switching field distribution.