Root locus method for plotting hysteresis loops of ferromagnetic thin films

SINCE BLOIS´ ORIGINAL publication1 on the magnetic properties of oriented evaporated thin permalloy films, much work has been carried out1¿7 in view of the potential application of such films in digital switching and storage. Mostly restricted to the nonmagneto-strictive composition of nickel-iron alloys (permalloy 80¿20), these films are generally prepared by vacuum deposition onto a heated substrate. A uniaxial direction of easy magnetization may be induced, and, if the film thickness is sufficiently small, it behaves as a single domain,6 and may be switched by rotation from one remanent state to the other.