Local Atomic Arrangements in a Magnesiowustite Solid Solution

Quantitative studies of diffuse X-ray scattering and measurements of magnetization are reported for (Fe,Mg)O with 15.7 cation % Fe held in a reducing atmosphere at 1400°C and quenched. The diffuse scattering is greater for fast cooling than for slow cooling; in both cases, spinel precipitation occurs, but the amount is much larger in the latter case. From this scattering, short-range order parameters were determined for the clustering between cations, and displacements were obtained between cations and anions. From the magnetic measurements the size of magnetic Fe ion clusters was obtained. Computer simulations of the cation arrangement with the measured short-range order parameters indicate that the magnetic clusters cannot be accounted for by nearest-neighbor Fe^2+] clusters. However, clusters of Fe ions related by first- and/or second-neighbor vectors are of the size found from the magnetic data.