Dilute 57Fe Mössbauer Studies in Cu–Ni Alloys

Abstract

The 57Fe Mössbauer effect has been used to study the properties of iron as a dilute impurity in Cu–Ni alloys. Using either 0.5 at.% Fe as an absorber or 57Co as a source in Cu–Ni alloys, a doublet is observed. This is presumed to be a small, partially resolved magnetic hyperfine field (based on evidence presented elsewhere) and we examine the implications of this for Cu–Ni alloys which are normally considered nonmagnetic. Previously, the hyperfine field at 4°K was reported as undergoing a rapid decrease in value near the equiatomic composition: from 243 kG at 55 at.% Ni to 0 kG at 45 at.% Ni (both alloys are ferromagnetic at 4°K). The present work extends this study and finds that the magnetic field drops instead to the small value of 10 kG. This field is almost independent of Ni concentrations between 10 and 45% Ni (i.e., in both ferromagnetic and paramagnetic regions). It is temperature independent between 4.2° and 198°K, and is the same for either the source or absorber (0.5%). The Mössbauer results suggest an invartype effect occurs in this alloy system.