RF-sputtered chromium-cobalt films for high-density longitudinal magnetic recording

Layered chromium-cobalt films having the magnetic and physical properties required for high-density digital recording have been deposited by rf sputtering onto small pyrex samples and onto 35.6-cm (14 in) diameter aluminum substrates. The layered structure consists of a layer of chromium several hundred nanometers thick surmounted by a cobalt layer a few tens of nanometers thick. To permit actual recording measurements, disks were protected with rf-sputtered coatings of chromium, carbon or silicon dioxide about 100 nm thick. RF sputtering offers excellent adhesion and good process control and can deposit non-conducting protective layers. Coercivities from 300 to more than 800 Oe and remanence-thickness products from 0.08 to 0.025 G-cm have been achieved at squarenesses in excess of 0.8. Under testing through a Winchester-type interface, P50is reduced to 66% at comparable output voltage, signal-to-noise ratio is increased, and harmonic falloff is reduced compared to standard particulate disks.