Shu Chiba

Magnetic read-out head using induced RF permeability variation

A field-sensitive type single pole read-out head was trial-fabricated and its characteristics were studied. Play-back sensitivity in the lower recording frequency region declined as the thickness of the Ni-Fe film decreased, but in the higher recording frequency region the read-out output level was independent of Ni-Fe film thickness maintaining an almost constant level, much higher than conventional heads. The carrier-to-noise ratio is also good. These two results show that this type of head is well suited to highly sensitive magnetic read-out heads for high-density magnetic recording.

Magnetic reproduction system utilizing magnetic body as capacitor

A capacitance element includes as an interelectrode substance a magnetic body for detecting a magnetic field formed by a magnetic recording medium. A tuned circuit includes the capacitance element as a tuning element and receives a signal from a high-frequency oscillator. The magnetic characteristics of the magnetic body change with changes in the magnetic field formed by the magnetic recording medium. The high-frequency signal output from the tuned circuit changes with changes in the magnetic characteristics of the magnetic body. A detecting circuit detects the changes in the high-frequency signal output so as to reproduce signals recorded on the magnetic recording medium.

Magnetic Read-out Head Using Induced RF Permeability Variation in Ni-Fe Thin Film

A novel principle of magnetic readout is proposed which can extract a high-quality output from high-density recorded signals. The principle utilizes sharp RF permeability changes in a soft magnetic film due to a weak external field. This variation is caused by both magnetization rotation and ferromagnetic resonance. A magnetic readout head which operates on this novel principle has been trial-fabricated. The prototype head was evaluated using sinusoidal signals (0.5 to 10 MHz) which were saturation-recorded on a magnetic tape with a ferrite ring head (head gap 0.3 ?m, track width 100 ?m). The signal level reproduced at 0.5 MHz by the prototype head was at least 35.7 dB higher than that from a ring head, and for 5-MHz signals the output was from 17.6 to 22.5 dB higher. The carrier-to-noise ratio for a 5 MHz carrier (1 ?m wavelength) was from 44 to 47 dB, and was independent of the Ni-Fe film thickness.