Magnetic properties of garnet film suitable for magneto-optic transfer readout from magnetic tape

We used a magnetic transfer to magnetic garnet film to develop a system that can read out signals recorded in D-VTR magnetic tape. A key point to this system is developing garnet film that enables signal transfer with a minimum bit length (= 0.385μm). The garnet film must also have a Faraday effect large enough to produce the C/N (carrier-to-noise ratio) necessary for the system. We discuss the desirable magnetic properties of garnet film based on the analytical transfer model we developed. Ideal garnet films have a thickness of 0.3-0.5μm, a Faraday coefficient of 7.5 deg/μm or more and optical absorption of around 0.5/μm. We also discuss the required C/N for a given tape speed to keep a bit error rate of 10-4 or less and the experimentally obtained C/N.