Magnetic Hysteresis in Nickel-Cobalt Alloys

Abstract

The magnetic hysteresis loops have been determined ballistically on annealed nickel-cobalt alloys covering the whole composition range, and their shape, the remanence (I_R) and the coercive force (H_c) have been studied. It was found that the hysteresis loops of γ-phase alloys containing more than about 25% Co usually take an abnormal shape like those of Perminvar and Permalloy, seemingly indicating an as yet unknown, but probable, existence of some superlattice.
For γ-phase alloys, the observed I_R values are shown to lie between the two extreme theoretical values derived assuming either that all of the directions of easy magnetization in every crystal grains are energetically isotropic or that only one of them is preferred, and H_c as a function of the composition is discussed in terms of the magnetocrystalline anisotropy and magnetic strain energies. It is pointed out that both I_R and H_c in ε-phase alloys may be influenced by the presence of free magnetic poles at grain boundaries.