Relation between the Thermal Expansion Coefficient and the Magnetization in Fe-Ni Invar Alloys

Measurements of magnetization curves for Fe-Ni Invar alloys have been made at various temperatures between room temperatures and about 450°C. Specimens used were in a sphere shape, which were obtained from the same ingots that the specimens used for the thermal expansion measurements had been taken from. By comparing the results of the magnetization measurements with the observed temperature dependence of the thermal expansion coefficients, it was found that the anomalous part of the thermal expansion vs temperature curve can be well expressed with the quantity, \(2/3CMₛdMₛ/dT\), where C is a magneto-volume coupling constant and M s is the spontaneous magnetization.