Noise characterisation of barium ferrite dispersions

Structural changes in barium ferrite dispersions during the milling process have been investigated by using noise measurements of the remanent states (DC modulation noise). Doped barium ferrite particles mixed with solvents, self wetting resins and binders were dispersed using a bead mill. Samples e xtracted at intervals during the process were coated onto PET film and magn etically oriented before drying. Tapes slit from the coating were investiga ted for noise in terms of spectral and total noise power characteristics fo llowing the isothermal and DC remanent magnetisation processes. Results ind icated a general reduction in noise with milling time consistent with the b reak up of particle agglomerates. However, changes in the spectra as millin g progressed and an increase in noise at certain frequencies were attribute d to the formation of stacks as particles became more mobile. (C) 1999 Else vier Science B.V. All rights reserved.