Analysis of ferromagnetic removable hard disc media ageing by time of flight-energy elastic recoil detection analysis

Abstract

Time of flight-energy elastic recoil detection analysis (ToF-E ERDA) has been applied to study the ageing of commercial thin film hard discs. Samples from a standard commercial removable hard disc were subjected to accelerated ageing heat treatment in normal humidity from 90°C up to 240°C in steps of 30°C for 3 h each. A test using a high humidity environment at 90°C up to 40 h was also performed. The ToF-E ERDA was carried out using a 60 MeV 127I 11+ ion beam incident at 67.5° to the surface normal, and detecting recoils at 45° to the ion beam direction by measuring their time of flight and energy in a detector telescope. The magnetic thin film structure was assigned to be a CN x /Co/N–Cr/Ni–P multilayer. At temperatures higher than 180°C the CN x coating layer detoriated with an increase of surface oxygen and an N content reduction in the N–Cr layer.