Magnetovolume effects in invar alloys: Pressure dependence of the curie temperature

The pressure dependence of the Curie temperature, dTc/dP, is discussed in terms of a localized electron model where dTc/dP is related to the volume dependence of the exchange energy. This relation is expressed by J′ and J″, the first and second derivatives of the exchange integral J(r) with respect to the interatomic distance. A quantitative test is made for Fe–Ni alloys where J′ and J″ are known. A brief comparison is made with the results obtained in the itinerant electron model.