Multi-tapped magnetoresistive heads for magnetic tape tracking servo

A multi-tapped magnetoresistive (MR) stripe has been commercially fabricated as a tape head for evaluation as a potential tracking sensor for magnetic tape systems with dedicated servo. In this approach, two adjacent MR elements sharing a common bias current are each positioned halfway over a single 17.5 mu m wide servo track. The head leads provide signals from each of the MR elements which are separated 1.25 mu m by permanent magnets that provide longitudinal bias. Since this servo configuration uses a differential sensor with a simple square wave tracking pattern, the system can allow self servo formatting. The evaluation of these heads on a Metrum test stand with 1550 Oe Sony MP media has revealed a number of important features to consider in using such a head. On-track isolated transition responses of the multi-tapped elements are shown to be comparable to those from standard individual MR heads fabricated on the same wafer. Cross-track signal profiles show that two adjacent elements in the multi-tapped head can provide an approximately linear tracking error signal within +/-4 mu m of track center. Finally, sample position error signal results demonstrate the potential of this type of servo scheme.