FUNDAMENTAL WEAR STUDIES WITH MAGNETIC PARTICLES AND HEAD CLEANING AGENTS USED IN MAGNETIC TAPES

The wear properties of commonly used magnetic particles (CrO2, Co-gamm a-Fe2O3, metal particles (MP) and barium ferrite (BaFeO)) and head cle aning agents (HCAs) (Al2O3 and Cr2O3) were studied. A simple accelerat ed wear test method was used for the experimental study. This method u sed a standard polishing process on a chip module made of magnetic hea d material, substituting the studied magnetic particles or HCA slurry for the abrasive. The hardness, size and shape of the magnetic particl es and HCA determined their abrasivity. Magnetic particles with increa sing abrasivity were BaFeO, MP, Co-gamma-Fe2O3 and CrO2. MP at the int erface resulted in staining of the mating head surface. Cr2O3 was more abrasive (more efficient HCA) than Al2O3 when wearing against a ferri te head, but less abrasive when wearing against harder head materials. It is suggested that the HCA should be less than about 1 mu m in diam eter with a concentration of about 2-4 wt.% of magnetic particles in a magnetic coating to minimize head wear. A single particle wear model was developed to predict the wear rate when a hard particle was sandwi ched between a workpiece (softer than the abrasive particle) and a sof t polishing pad. This model indicated the increasing trend of the wear rate with an increase in the particle size and particle sharpness. Th e effect of the topography and mechanical properties of the polishing pad on the wear rate was also predicted by this model.