Neutron depolarisation and noise studies of Ba-ferrite tapes as a function of milling time

Ba-ferrite particles have been dispersed and coated onto polyethylene terephthalate (PET) film and magnetic structure investigated using a range of magnetic measurements including noise studies and neutron depolarisation (ND). Noise measurements were made on lengths of tape for samples cycled through Isothermal Remanent Magnetisation (IRM) and DC Demagnetisation (DCD) measurement processes and interpreted in terms of the total noise power and spectral response. ND measurements were analysed in terms of magnetic correlations within the films. Total noise power exhibited a minimum around the remanent coercivity (H_r), as observed for most particulate media. ND values of correlation function, ζ displayed a peak rather than a dip around H_r. The similarity in the respective peak/dip positions indicates that both measurement techniques were sensitive to the same micro-structural details