Thomas Daniel Carr

A new high density magnetoresistive tape head

An 8-track magnetic tape head for high-frequency, high-density applications is described. It includes an unshielded magnetoresistive read head and two thin-film record heads for bidirectional operation with write verification. The MR sensors are biased by specially shaped thin-film permanent magnets (PM) that provide fields along both sensor axes to linearize output and eliminate Barkhausen noise. Nearly all films in the head are deposited using dry processes. Deposition conditions for the PM have been optimized to produce a high-coercivity, high-remanence isotropic film. The final head assembly has a contour that utilizes longitudinal slots to achieve intimate contact with low head-to-tape pressure. The associated data channel uses both read and write equalization to obtain the desired output pulse shape from the unshielded head. >

Modulation noise measurements of high density recording channels using MR heads

Modulation noise measurements were made on several tape samples using an unshielded magnetoresistive (MR) head. The very high sensitivity of the MR head makes possible the detection of the media noise above other noise sources not associated with the recording medium, such as head resistance and preamplifier noise. The effect of track width on modulation noise was investigated. It has been shown previously that modulation noise, which is multiplicative in nature, is not purely Gaussian but also contains a significant exponential component. The implications of the non-Gaussian nature of this noise for amplitude qualifier level setting and for error rates in peak-detecting and partial-response channels are discussed. >