INVAR AND VOLUME MAGNETOSTRICTION

The Invar effect is discussed from the standpoint of volume magnetostriction, which in Invar alloys is assumed to result from direct exchange between neighboring magnetic ions. Direct exchange integrals are evaluated from the cohesive energy using published data on the pressure dependence of the compressibility. The use of these values gives a good account of the Invar effect in Ni-Fe alloys. The anomalous compressibility of Invar is also discussed, and an explanation is suggested for the temperature dependence of the volume magnetostriction in bcc Fe. © 1979.