Photothermally modulated playback from a magnetic tape

A novel method is presented which allows spatially resolved detection of magnetic signals from tapes. The PM-playback signal is generated in the head of a tape recorder by thermal modulation of the magnetization of the stationary tape. The PM-playback has been observed from homogeneously magnetized Fe2O3, CrO2 and ferrochrome tapes and from a sinusoidal track recorded on a CrO2 tape. From the signals measured as a function of laser spot position and of modulation frequency the depth and lateral variation of the magnetisation has been determined