A magneto-optic readout head using a high permeability flux carrier

A conventional readout head using a magneto-optical effect has the following two problems: (1) Readout of a bit that is shorter than laser spot size is difficult, and, (2) It cannot make contact with the recording medium. A new type of magnetic head using a magneto-optical effect that has been developed and is described in this paper is aimed at overcoming these problems by introducing a high permeability magnetic thin film. We applied this head to a readout of the signals recorded on a flexible disk. Readout C/N was improved by a thick (0.6 μm) high permeability film and using a magnetic garnet film with more satisfactory characteristics (Ms was low, the Faraday rotation angle was large). A readout laser of small spot size also improved C/N remarkably. However, noise increased at recorded wavelengths longer than λ=10 μm. A C/N of 45 dB was obtained at λ=10 μm. The reproduced signal levels were almost constant in spite of the change in disk rotation speeds.