EFFECT OF SURFACE ROUGHNESS ON SUSCEPTIBILITY OF THIN PERMALLOY FILMS

80/20 NiFe films were produced on cleaved and polished (to remove cleavage steps) substrates of NaCl at various temperatures, and measured using the biased susceptibility method developed by Feldtkeller. Films on the polished substrate showed anomalous behaviour including a decrease in the susceptibility, an increase in the rotational hysteresis and a constant internal field. These characteristics are explained by assuming the films to be highly dispersed and applying the ripple theory due to Harte. There is very good agreement with this theory and it is shown that the high dispersion caused by the surface roughness is probably due to the scratches incurred whilst polishing rather than any variation in the mode of growth. Rotatable initial susceptibility was observed in both types of films, and is thought to be due to inhomogeneous stresses in the film. The biaxial anisotropy which could be caused by the fine structure of the scratches, in a similar manner to that described by Prosen et al. in 1963, was not observed.