Magnetostriction of Fe–Ni Invar Alloys

Magnetostriction of fcc Fe–Ni alloys was measured by means of the paper strain gauge in the temperature range of 4.2 K to 296 K. The temperature dependence of spontaneous magnetostriction constant λ 111 was positive, while λ 100 was negative for all the alloys in the whole temperature range. The composition dependence of constants at room temperature was in good agreement with previous reports. The forced magnetostriction of alloys less than 40% Ni increases abruptly with a decrease of Ni composition in the temperature range between 4.2 K and 296 K. The thermal expansion coefficient of the single crystal was also measured. The anisotropic behavior was observed below about 50 K.