Short-range ordering and ferromagnetic properties of disordered Au₄Mn alloy

Abstract

The short-range-order (SRO) parameters of disordered Au4Mn alloy were determined from an analysis of the X-ray diffuse scattering with the use of Borie & Sparks [Acta Cryst. (1971), A27, 198-201] separation techniques. On the basis of the observed SRO parameters the local Mn atom arrangement in the f.c.c. lattice was constructed using a computer simulation method. The Mn atoms in the SRO state were found to form a three-dimensional irregular network which is linked mainly by linear chain segments along the [100] directions and also with nearest-neighbour relations. The Mn atom arrangement is the first example to show the structure expected from a random spin system with a concentration gradient. The ferromagnetic properties of this state can be well understood on the basis of the structure.