Improvements in Corrosion Resistance of Tb-Fe Thin Films

Amorphous rare earth-transition metal thin films (RE-TM films) have properties suited for erasable optical memory media. They have been widely studied and will be soon in a step of practical use. These films, however, have the drawback of poor reliability due to their poor corrosion resistance. We have reported that the corrosion of the films is classified as being the surface oxidation, the selective oxidation of RE metals, and electrochemical corrosion.1,2 To protect the RE-TM films from the corrosion, two methods can be considered. One method is to improve the corrosion resistance of the films themselves. The other is to coat the films with protective layers such as SiO, AIN.3 We have studied the electrochemical corrosion of RE–TM films immersed in a NaCl aqueous solution and succeeded in improving the corrosion resistance of the films themselves by adding several metals.