Magnetic permeability measurements in GMR multilayers with extra-thick magnetic layers

Initial permeability and transverse bias permeability measurements have been made on [NiFeCo(t)/Cu(23 /spl Aring/)]16 multilayers for different magnetic layer thicknesses(t) in the as-deposited state and after an annealing treatment. The initial permeability was found to be independent of frequency up to at least 100 MHz and to increase with magnetic layer thickness. The transverse bias permeability is used to calculate the effective uniaxial anisotropy and the bilinear and biquadratic exchange fields. The thicker multilayers are found to be ferromagnetically coupled in the as-deposited state and upon annealing a transition occurs producing antiferromagnetically coupled magnetic layers.