Tohru Fujimaki

A Magnetic Coil Suitable for Magneto-Optical Recording with a Large Working Distance

A first surface magneto-optical (MO) system has a high storage density and a high data-transfer rate. The high-density recording is achieved using a blue laser and lenses that have a high numerical aperture (more than 0.85) and that are integrated with a magnetic-field modulation coil. If the working distance is more than 30 µm, the optical head can be controlled by using a mechanical actuator, for which many existing technologies are available. We have developed a magnetic coil suitable for working distances of up to 30 µm. First, we analyzed the relationship between the properties of a magnetic layer and a magnetic field and then from our analysis derived three design concepts. We then designed a magnetic coil with a fan-shaped magnetic layer composed of stick-shaped magnetic bodies and heat sinks; testing showed that it can be driven at a data transfer rate of 80 Mbps and that it has a wide temperature margin.