Measurement of magnetic correlation effects in particulate recording media

Noise and neutron depolarization (ND) measurements on a particulate recording tape at various remanent states through the DC demagnetization remanence curve are presented. The microstructure of the tape is discussed in relation to both media noise and a correlation length, xi , derived from a ND experiment. The ND correlation length perpendicular to the plane of the tape is found to be on the order of the particle size at all values m of the remanent magnetization after DC demagnetizing along the length direction of the tape, although a weak variation in xi with m is also observed. From the ND experiments, superdomains elongated along the direction of the applied field have been deduced. An increase of the noise power with increasing m has been found. This increase may be due to small density variations within the coating of the tape or to an increase in the size of the superdomains along the length direction of the tape with increasing m. The magnetic microstructure after bulk erasing clearly differs from the magnetic microstructure after DC demagnetizing.<
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