Magnetic and magneto-photoellipsometric evaluation of corrosion in metal-particle media

The authors describe a magnetooptical (MO) measurement technique by which the surface degradation of metal particle (MP) tape exposed to a high-humidity/high-temperature environment may be detected with relatively high sensitivity. It is demonstrated that, using the concept of the Arrhenius plot, these measurements may be used to provide useful information on the archivability of these tapes. Surface-dependent MO measurements are shown to be better suited to the detection of the onset of corrosion in MP media than methods based on volumetric considerations. At the wavelength chosen the skin depth can be shown to be on the order of 110 nm. This is a significant fraction of the recording depth in the medium at very high bandwidths and is, moreover, the most important fraction. Once an acceptable fractional drop in Kerr signal (correlated with, say, bit error rate) has been established, it is possible to estimate with some confidence of the archival lifetime of any MP tape for a variety of ambient conditions