Thermal Expansion Coefficient of Fe–Ni Invar Alloys at Low Temperatures

Abstract

Thermal expansion coefficient of Fe–Ni Invar alloys at low temperatures has been examined by using the itinerant electron model. It has been found that the experimental values obtained by Schlosser et al. and by Zakharov and Fedotov could be explained satisfactorily up to about 200 K by using the expression derived in the present paper which has three terms, the normal lattice term, the spin wave term which is proportional to T^1⁄2 and the single particle excitation term proportional to T.