Relation of permeability and hysteresis to atomic magnetostriction.—In permalloy, as shown in the preceding paper, magnetostriction changes sign at about 81 percent Ni, hysteresis losses can be made vanishingly small near this composition, and these effects are not due to the special alignment of crystals. It is suggested that in every ferromagnetic material the process of magnetization involves (1) intra-atomic changes, presumably changes in the orientation of electron orbits, governed by quantum dynamics and independent of environment; and (2) inter-atomic changes (stresses and strains). The inter-dependence of the inter-atomic changes and the intra-atomic changes is conveniently described as atomic magnetostriction. On this view, hysteresis loss and magnetic hardness are due to the energy required to produce, in succession, the local deformations associated with changes in the magnetization of single atoms or small groups of atoms. High initial permeability and low hysteresis loss in permalloy are explained as resulting from locally compensatory atomic magnetostrictions of the nickel and iron atoms in small groups. The fundamental differences in the magnetic behavior of Fe, Ni and Co are attributed to differences in their atomic magnetostrictions. Other differences are attributed to differences in the mechanical properties which alter the energy expended when atomic magnetostriction takes place.

Close

PrevNext

View figure in article