The future of particulate rigid disks

Abstract

In recent years, there has been a strong movement away from the traditional Co-modified iron oxide particulate media and toward thin film metallic media used in small rigid disk systems. The main reason for this change is due-to the fact that these traditional particulate media cannot satisfy the requirements for high density recording because of recording and self-demagnetization losses resulting from their wide switching field distributions. The use of much higher coercivities, affected primarily by increasing the amount of adsorbed cobalt, which might have reduced the problem, is precluded on account of the ensuing large increases in the thermal coefficient of the coercivity. The employment of metal particles, which can provide the high coercivities without the thermal instabilities, is also precluded because of their susceptibility to corrosion. These problems are circumvented by using oriented particulate dispersions of Ba-ferrite platelets, which have extremely sharp switching field distributions and almost square remanence loops. Their high density recording characteristics compare well with those of very high coercivity thin film media and are far superior to those of Co-gamma media of similar coercivity. Furthermore, they offer significant cost advantages, particularly for larger diameter disks.