Antiferromagnetic Characteristics of Cr–Sn and Cr–Fe Alloys, and Nonferromagnetic Cr–Fe–Sn Invar Alloys

Invar alloys are widely used as materials for precision instruments. The practical Invar alloys are all ferromagnetic, and the ferromagnetism of these alloys often limits the scope of their application. In recent years, therefore, considerable attention has been directed to the research and development of nonferromagnetic Invar alloys. Cr is an antiferromagnetic material and its physical properties such as thermal expansivity and electrical resistivity change anomalously near the Neel temperature. These properties are sensibly modified by the addition of other elements. The present authors investigated the temperature dependence of the physical properties for some Cr-base primary solid solution alloys. With the addition of Sn, the Neel temperature of Cr increases up to 2.0% Sn and then decreases gradually, and the thermal expansion coefficient below the Neel temperature becomes smaller. The Neel temperature in the Cr-Fe system decreases with increasing Fe concentration, while the thermal expansivity does not show any regular dependences on temperature and concentration. Taking the above-mentioned results into consideration, the thermal expansivity and the magnetic susceptibility of the Cr-Fe-Sn alloys in the range of the primary solid solution have been measured. The results show that the alloys are of the antiferromagnetic Invar type and their magnetic susceptibility is negligibly small.