MAGNETIC DOMAIN-STRUCTURES IN MULTILAYERED NIFE FILMS

The coercivity of NiFe (80/20) films can be lowered by laminating several layers with nonmagnetic spacers. A reduction by a factor of 10 can be achieved with a simple bi-layer, regardless of spacer material, provided the spacer thickness is below a critical value. No further reduction is found for multilayers. Two peaks of Hc near thicknesses of 250Å and 1000Å for single layer films, associated with changes in domain structure, are suppressed by lamination. After a minimum spacer thickness (S) of 10-15Å, the domain walls in the separate layers no longer coincide but track closely, their separation depending on S. With S?100Å the layers switch independently, giving rise to multiple values of Hc.