Angewandte Chemie International Edition
Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 11/1989)
The cover picture shows a pattern of data (0,1,0,1,0…)—pits—on a magneto-optic storage disk which is read with a semiconductor laser. The storage medium is a lanthanoid-transition metal alloy, whose magnetism is directed upwards and perpendicular to the disk. In the bright domains (ca. 1 μm) the magnetization is directed perpendicularly downwards. The plane of polarized light is rotated by the data pits, so that the magnetization pattern can be observed with a microscope. The data are read with the laser beam according to a similar principle. For determining the dynamic write-read properties, pits have been marked with three different frequencies. Guide grooves in the surface serve for orientation on the disk. More about materials for optical data storage is reported by M. Emmelius et al. on page 1475 ff.