Magnetizable recording disk and disk file employing servo sector head

Abstract

A magnetizable recording disk is divided into data and servo sectors. The servo sectors include position reference information comprising a circumferentially extending and radially repeated magnetization pattern. Each such pattern comprises at least three subsets of elements from each of which a different phase of radial position error signal, indicating displacement from a data track center line, can be derived. The subsets are radially offset from each other by less than the pitch of the data tracks and their individual elements each have a radial width greater than the pitch of a data track. By making the width of the individual element of the servo pattern greater than that of the data tracks and, necessarily, greater than the physical width of the electromagnetic transducing head for reading and writing information on the disk, the contribution of neighboring elements to the signal sensed by the head via its fringing field is reduced. This results in a more linear position error signal in all regions where the head straddles the boundary between elements. A disk file comprising such a disk comprises, in addition to the electromagnetic transducing head, a head positioning actuator, position error signal generating means for generating the multiple phase position error signals and combining them into a composite signal and feedback means for feeding back the composite position error signal to control the actuator to correct for displacement of the head from a selected data track center line.