The cylindrical symmetry of the angular distribution of particles in magnetic tapes

To understand the writing process in magnetic recording, it is necessary to take account of the perpendicular component of magnetization in the coating as well as the in-plane component. To do this, we need to determine the shape of the magnetization curve in the perpendicular direction. We have measured this magnetization curve for eighteen samples of tape whose thicknesses ranged from 2.5 μm to 10 μm and orientation ratios from 1.0 to 3.0 and corrected each curve for the effects of demagnetization, Comparing each of these curves with the curve measured in the transverse direction, we found that the ratio of transverse remanence to perpendicular remanence (corrected for demagnetization) was 1.092, standard deviation 0.166. Two disk-shaped samples were further measured as a function of the angle ψ where (90-ψ) is the angle between the field direction and the polar axis of the sample. Our conclusion is that for these tape coatings the angular distribution of particles was cylindrically symmetric about the direction of coating within about 10%. Consequently, it is possible to determine the magnetization curves of the coatings in the perpendicular direction from measurements made in the transverse direction.