Long-Term Magnetization Stability of Data Storage Tape Prepared from Ultrafine Metal Particles

We examined the time dependence of the relative magnetization (M
_rela
) and the relative permanent magnetization loss (M
_loss
) due to the oxidation in data storage tape prepared from ultrafine metal particulate (MP) composite in the preserving temperature range from 295 to 348 K for 1000 h. We also investigated the optimum stabilized condition at 295 K for 5000 h after demagnetization by initially applying the reverse field. The time dependence of the change in M
_rela
with no reverse field and the M
_loss
of MP tape were negligible at 295 K for 1000 h. However, the value of M
_loss
at above 338 K increased rapidly after 100 h had elapsed. It may be closely related to the oxidation of MP particles. The change in (M
_rela-
M
_loss
) was proportional to the logarithm of time for 1000 h at 295 to 348 K. The magnetization value at 295 K could be stabilized over 5000 h by initially applying the reverse field. During the time dependence of magnetization obeyed a logarithmic law, the optimum demagnetizing field for stabilization agreed very well with the critical field of magnetic aftereffect.