Stability and microstructural phenomena in RE-TM films for thermo-magneto-optic recording

TbFe films have been subjected to aging treatments over a range of temperatures and relative humidities. Magnetic, optical and microstructural measurements show that the properties of unprotected films deteriorate rapidly with time, particularly in high relative humidities. Films coated with protective aluminium or aluminium nitride layers are generally far more stable but cannot tolerate high humidities. The process of corrosion is associated with the preferential oxidation of the rare earth leading to local diffusion and segregation of iron. Large scale corrosion is particularly serious at pinholes or other obvious defects in the deposited films. These variations in composition and structural inhomogeneities correlate well with magnetic measurements.