Abstract: A magnetic disc memory having a device for positioning a magnetic head on a track. A disc is sub-divided into sectors comprising groups of data tracks and, alternating therewith, sectors having groups of servo tracks which define the data tracks which are staggered over one half track pitch with respect thereto. Each servo track includes magnetization changes (reference transitions) for reference purposes. Magnetization changes for position detection purposes (measuring transitions) are present in the servo sectors, stepwise from track to track per group of servo tracks. Said stepwise magnetization changes are of alternating polarity from track to track. An additional transition is provided every other servo track in the vicinity of the reference transitions. A stepwise organization of the magnetization changes in two longitudinal directions of the servo tracks enables the number of tracks per group to be substantially doubled.