The volume change at the Curie temperature is analyzed according to the local-band theory of itinerant ferromagnetism. It is related to the volume coefficient of the Bloch wall stiffness. Plausible assumptions, in a simple one-band model, give the correct values for iron and nickel. A more speculative argument yields a good value for the Invar alloy ${\mathrm{Fe}}_{65}$${\mathrm{Ni}}_{35}$ as well.

• Received 29 June 1981

DOI:https://doi.org/10.1103/PhysRevB.24.5413