Magnetovolume Effects in Ferromagnetic Transition Metals

Magnetovolume effects in ferromagnetic transition metals and alloys, such as the spontaneous volume magnetostriction, the forced volume magnetostriction, are described by a phenomenological theory based upon a fluctuating local band picture, in which both itinerant electron and local moment characters are taken into account. The magnetovolume effects of Fe, Ni and the Fe-Ni Invar alloy are analyzed on the basis of the proposed theory. It has been shown that the degree of shrinkage of local moments above the Curie temperature can be estimated from this analysis. It is concluded that local moments remain almost unchanged in bcc Fe and, on the contrary, they shrink markedly in the Invar alloy.