In a tape data storage arrangement, a magnetic detent is provided to maintain a tape read/write head in selected positions with respect to the tape, during data transfer. The tape is mounted on a carriage movable between first and second positions, with respect to a support structure, and a detent member is fixably joined to the support structure. First and second detent components mounted on the carriage engage the detent member by means of a magnetic force, when the carriage is moved to the first and second positions, respectively. Usefully, the detent member is a magnet and the first and second components comprise steel. Alternatively, the detent member comprises steel, and the first and second components are both magnets.