Thermo-magneto-optic materials for high density data storage

The search for suitable materials for thermo-magnetic recording (TMR) and the concurrent development of thermo-magnetic-optic (TMO) erasable disk systems has led to impressive improvements. Of particular interest have been various homogeneous rare earth/transition metal (RE-TM) alloys-binary, ternary and quaternary-and a general approach to the empirical categorisation of these different alloys is now fairly well established. The author discusses the principles of TMR and the development of TMO materials. Particular emphasis is placed on how the amorphous RE-TM alloy films and the more recently developed metallic multi-layer films satisfy the desirable material requirements for TMR. The medium used for most disks is based on the ternary TbFeCo, although TbFe, TbCo, GdTbFe, GdTbCo and some quaternary alloys have also been used successfully