AGING EFFECTS OF METAL EVAPORATED TAPES

We have investigated the ageing effects of Metal Evaporated (ME) tapes stored under different temperature and humidity conditions. The obser ved increase of the longitudinal coercivity measured parallel to the r unning 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-c-increase is mainly determined by the storage humidity, the sp eed of the ageing is dominated by the storage temperature. The output level of the ME tape measured with a video ring head is not deteriorat ed by the climate storage. As the ageing behaviour is not at all influ enced even by very thick (100 nm) C or Cr protective layers we conclud e that the physical process causing the ageing consists in the oxidizi ng influence of evaporates from the PET substrate foil on the magnetic material.