Narrow track readout with magnetic garnet film

Abstract

A novel magneto-optic readout head, which utilizes the modulation of width of straight domains in a garnet film in response to the fringing field from the recording medium, was evaluated from the viewpoint of narrow track readout. In a static transfer experiment with a garnet film having a domain width of 2.25 μm, a definite transfer to the garnet film with track widths of 3 μm or less was confirmed. An expression for the modulation degree of the domain width was derived, and its predictions agreed well with the experimental results. In the dynamic readout experiment, a carrier-to-noise ratio of 50 dB was obtained for a trackwidth of 4 μm and a wavelength of 10 μm. The cross-talk was -30 dB when the track-to-track spacing and track width were 10 μm and 5 μm, respectively. From these results the feasibility of narrow track readout based on this head was demonstrated. The readout performance, including the decrease of readable track width, the wavelength and crosstalk, can be greatly improved if a garnet film, having a domain width narrower than that used in this experiment is used together with a high-density recording medium.