Narrow track defect studies on flexible media

In the last decade, interest in increasing digital storage density on flexible media has resulted in an improvement from less than 1.5 . 10²bits/mm²to more than 1.5 . 10³bits/mm². This remarkable increase has been possible due to new and improved recording configurations as well as enhanced media and head designs. In order for flexible media magnetic recording technology to maintain its competitive edge, recording densities will have to increase in the next decade by at least another order of magnitude. This, clearly, can be achieved only by pushing both linear and track densities simultaneously toward their respective limits. While linear densities on digitally recorded flexible media have been investigated up to densities approaching 4 . 10³flux changes/mm, track densities on flexible media have attained values exceeding 4 tracks/mm only in a few isolated cases. In fact, it is commonly assumed that it would be much easier to increase linear densities than track densities because of dimensional substrate stability as well as defect and noise considerations. On the other hand, it is essential to understand the factors that influence track densities since in terms of recording parameters this should be the most direct way to further increase storage density. In this paper we have studied the defect behavior of flexible media at high track densities (i.e., very narrow trackwidths) and at varying linear densities. In particular, we have investigated the relationship between drop-out length and trackwidth as a function of recording density for trackwidths of 12.5, 25, 55, 112, and 150 μm, respectively, using commercially available media. The analysis of the defect statistics leads us to conjecture that the depth extension of the defects as well as their area must be taken in account in defect modeling. A qualitative description of the effect of such defects will be discussed together with its meaning for high density recording.