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A range of CoCrPt thin film discs sputtered on CrV underlayers have been prepared under varying base pressures. A general improvement in H, squareness [S.sup.*] and recording performance determined by the media SNR was seen when the base pressure was reduced. Electron diffraction studies have clearly shown that a significant proportion of fcc grains are induced when a high base pressure is allowed to remain in the chamber and this is consistent with the presence of residual nitrogen gas in the system. Index terms - thin film media, magnetic properties, sputtering conditions, stacking faults.

A non-destructive technique to measure the time dependence of remanent coercivity in thin film disks is suggested. It is found that typical thin film recording media show an increase in coercivity of about 25% when the length of the field pulse is decreased from [approximately] 50 ms down to 10 ns. Very thin magnetic films are found to have considerably larger changes in coercivity than thicker ones. Index Terms - Magnetic viscosity, reptation, reverse dc erase noise, thin film media.