Properties of Amorphous Rare Earth-Transition Metals thin films for magnetooptical recording

Amorphous RE-TM alloys thin film can be used as high density storage media for magnetooptieal (M.O.) recording. The poor reading efficiency of these alloys can be enhanced if they are deposited in a multilayered structure computed to combine M.O. and interference effects. The perfect rectangularity in the inductive and magnetooptic hysteresis cycles is attributed to the large value of the quality factor Q = Ku/2πMs²which can be much larger than that of other perpendicular recording materials such as CrCo. The magnetization process of RE-Fe film occurs by domain nucleation and domain wall motion which are assumed to be thermally activated. Aging phenomena are observed on GdCo, GdFe and TbFe which are due to the oxidization of RE atoms. In the case of SiO2- protected GdFe films the aging phenomena at room temperature are attributed to the segregation of RE atoms which build up a nonpermeable layer when they oxidize. RE atoms can diffuse in the RE-TM amorphous layer as can be seen by the change in the magnetic properties which occurs when RE atoms are deposited below and above the magnetic film. The consequences of these properties on the use of RE-TM films as M.O. recording media are discussed.