A scanning device for scanning data-carrying disks. The disks include a magnetisable layer to and from which data is written and read using a magnetic transducer, such as a Giant Magneto-Resistive (GMR) transducer. Positioning of the transducer over a data track is achieved by optical tracking using a land/groove structure, and positioning of the transducer with respect to the optical tracking system by means of a reference beam transmitted through the disk.