Ageing effects of metal evaporated tapes

The ageing effects of metal evaporated (ME) tapes stored under different temperature and humidity conditions are investigated. The observed increase of the longitudinal coercivity measured parallel to the running direction of the tape with a vibrating sample magnetometer can in all cases be described by an exponential law. Whereas the extent of the H/sub c/-increase is mainly determined by the storage humidity, the speed of the ageing is dominated by the storage temperature. The output level of the ME tape measured with a video ring head is not deteriorated by the climate storage. As the ageing behavior is not at all influenced even by very thick (100 nm) C or Cr protective layers it is concluded that the physical process causing the ageing consists in the oxidizing influence of evaporants from the PET substrate foil on the magnetic material.<>