The origins of defects in sputtered Co-Cr perpendicular magnetic recording media

The authors examine various causes of contamination and the defects they produce, and they typify some defects that originate at the metal/substrate interface, as nodules or extraordinary particles. They find that these are not caused by dirt or mishandling, but are induced by an exudate from the polymide substrates used. The nodules´ characteristic acorn shape can be analyzed mathematically to suggest a possible exudate-induced mechanism for their formation and growth. The authors conclude that most of these defects can be eliminated