Thickness dependence of magnetic properties and noise characteristics of Co obliquely evaporated tape

Co obliquely evaporated tape has the potential for a very high signal output. The dependence of the magnetic properties and noise characteristics on the magnetic layer thickness was investigated. Co thin films were deposited using web-coater-type vacuum evaporation equipment. As the magnetic layer thickness (δ) increases, the signal output level increases at first and saturates at about δ=λ/4, while the medium noise (AC-erased and modulation noise) level monotonically increases. Carrier-to-noise ratio for λ=0.54 μm has a peak at about σ=1300 A. The irregular configuration of the magnetic transition area was observed for thick layer samples by Bitter patterns. The microstructure of the magnetic layer suggests that the increase in the modulation noise can be attributed to the morphological features of the column and the cluster. The reversal field distribution broadens with the increase of δ, which makes the magnetic transition area large and might make the transition irregular