Transfer Films and their Effect on Signal Errors for Helical Scan Data Tape Recording Systems

Abstract

‘Transfer deposits’ or ‘staining’ on a magnetic recording heads causes spacing losses at very high recording densities, resulting in signal degradation when reading or writing of data from a magnetic tape. The aims of this project, which is funded by Hewlett Packard, are to understand and establish the mechanism of head stain and to determine the physical/chemical changes that occur at the head-tape interface of a helical scan DDS Digital Data Storage system. AES results show head stain mainly consist of magnetic particles in the form of gamma iron oxide (y-Fe2,O3), which are transferred from the surface of the tape to the surface of the head. Further tape cycling showed at 25°C/35%RH (high water vapour content) stain was deposited on the glass region only of the read head. Whereas at 40°C/10%RH (lower water vapour content) stain was deposited on both the glass and ferrite regions of the read head and the stain thickness increase on the glass and ferrite regions of the read head as the tape was cycled. The results indicate that the error rate is approximately directly proportional to the average stain thickness at 25°C/35%RH and 40°C/10%RH. In addition it was found that the thickness of the stain is dependant on the humidity, temperature, the number of tape cycles and abrasivity of the tape (tape roughness). The average head wear (= tape roughness) for 25°C/35%RH and 40°C/10%RH is directly proportional to the power of number of tape cycles, where the average head wear rate is a function of the number of tape cycles, humidity and temperature. The results presented show that the surface roughness of DDS tape decreases that is the tape becomes smoother as the tape was cycled and the surface roughness after 5000 tape cycles are independent to the humidity and temperature for 25°C/35%RH and 40°C/10%RH. The results indicate that the tape smoothing correlates with the reduction in the head wear rate as the tape was cycled. Further research work would include expanding the humidity and temperature combination such as 5°C/35%RH, 5°C/10%RH, 25°C/80%RH, 40°C/35%RH, 40°C/80%RH and 10°C/10%RH: develop a method of measuring the areal coverage of the stain; devise a technique of measuring the surface adhesion forces of the stain, at ferrite and glass regions of the inductive head and tape.