Wiepke Folkerts

TRENDS IN DIGITAL MAGNETIC RECORDING; THE APPLICATION OF THIN-FILM HEADS FOR TAPE RECORDING

Abstract Digital tape recording systems show the same trend as hard-disk drives: a large increase of storage density with time. The use of advanced media and highly sensitive thin-film heads with magnetoresistive (MR) readout will increase the storage density dramatically. Key improvements are narrower tracks, more sensitive MR elements attained by applying the giant magnetoresistance effect, high-saturation flux density pole materials, advanced metal powder tape, intimate head-to-tape contact, and accurate tracking. By increasing the number of channels in the multitrack thin-film head, high data rates can be obtained as well. The basics of digital magnetic recording are discussed and a short historical overview is given of the Philips activities on thin-film heads for tape recording. An outlook on future improvements is given.

Giant magnetoresistance and its application in recording heads

A short overview is given of the giant magnetoresistance (GMR) effect and its device applications. As an example of present research topics, the optimization of the ferromagnetic-layer composition of spin valves for application in recording heads is discussed. The influence on output voltage and stability has been investigated in test structures and compared with material parameters that were experimentally obtained from unpatterned films. It is found that in practical applications a small addition of cobalt is advantageous, since, although the output voltage is decreased, it leads to an improvement in reproducibility, linearity, signal-to-noise ratio and dynamic range.