Fabrication of narrow-track-video-head with sendust-sputtered film

For the purpose of getting the core material for the narrow-track magnetic head for video signal recording, thick magnetic film was deposited by the plasma-arc-sputtering technique and the operating characteristics of the head made from the film were examined. The results are as follows. 1) Sendust films up to 55 μm thick were able to form by the sputtering technique. 2) A mechanically hard film having a Vicker´s hardness of 740 was obtained (hardness of bulk Sendust is 510). 3) The permeability of the film was located between the permeability of the super-finished sample and that of the etched one of bulk Sendust in the frequency range 1 MHz to 20 MHz (μ´ is 60 at 9 MHz at the film thickness 30 μm). 4) With the experimental head whose track width is the same as the film thickness (22 μm), the sinusoidat wave signal up to 8 MHz was able to record and reproduce with the velocity 50m/s. 5) The picture signal of 1 TV field was recorded on one track of the magnetic sheet rotating at 60r/s. The resolution of the reproduced picture was 300 TV lines and the signal-to-noise ratio was 43 dB (p-p/rms).