PURPOSE: To prevent a degradation in output by use or preservation at a high temp. and an increase in off-track quantity by forming a magnetic layer on a flexible base, then subjecting the base molded to a use shape to a heat treatment while the base is fixed, thereby enhancing the thermal stability thereof and uniformizing the same in all bearings.
CONSTITUTION: After the magnetic layer is formed on the flexible base, the base is molded to the use shape as a magnetic recording medium such as a circular cookie like, for example, floppy disk and this molding is fixed partially or over the entire part and is subjected to the heat treatment at 55W96°C. Burst signals for alignment are written in all the tracks of such magnetic recording medium. The off-track quantity of the burst signals for alignment of this magnetic recording medium with respect to the track width is specified to ≤4.0% when the above-mentioned recording medium is rested for 24hr at 60°C, then 30hr at a room temp. The magnetic layer of a coating type formed by using hexagonal Ba ferrite as magnetic powder is effective and the flexible base essentially consisting of polyethylene terephthalate is more preferable.