Magnetic Susceptibility of Au–Fe Alloys

Abstract

Over the past years there has been considerable interest in the magnetic properties of the Au(Fe) system. Mössbauer measurements indicate that a complicated type of long-range ordering occurs below concentrations c of ∼12 at.% Fe and extends down to c<1%. Yet no definitive susceptibility study has been carried out over a complete range of temperatures and concentrations in order to characterize the magnetic ordering. We have measured the low-field magnetic susceptibility χ(T) for a series of eight Au–Fe alloys (1–22 at.% Fe), and we observe a definite peak in χ at those ordering temperatures determined from the Mössbauer data. The magnitude of χ greatly increases with c, while the shape of χ(T) in the region of the peak changes from a cusp-like behavior at low c to a behavior for c≳17% in which χ(T) gently rises, then sharply falls. These behaviors confirm the existence of a long-range order suggtesive of antiferromagnetism at low c (≤8%) with a more typical ferromagnetic ordering at high c. At intermediate c (≈12%), χ(T) seems to indicate the presence of a mixed type of long-range order.