The crystal structure and magnetic properties of a new series of ordered double-perovskite oxides Sr2FexMo2−xO6 (0.8 ≤ x ≤ 1.5) have been studied. The crystal structure changes from a tetragonal I4/mmm lattice to a cubic Fm3̄m lattice around x = 1.2. The degree of ordering in Sr2FexMo2−xO6 exhibits a maximal at x = 0.95 and decreases as x deviates from 0.95. The saturated magnetization increases from x = 0.8 to 0.95 and then decreases from x = 0.95 to 1.5. The Curie temperature exhibits an abrupt drop around x = 1.2, where the structural transition takes place. These complex behaviours are strongly correlated to antisite defect concentration in the compounds.

The structure and magnetic properties of a ternary intermetallic compound Gd 3 Fe 28 Re stabilized by Re in the sixth period has been investigated by means of XRD analysis and magnetic measurement. The compound crystallizes in the monoclinic Nd 3 (Fe,Ti) 29 -type structure with space group A2/m. The lattice parameters are a = 10.5778(1) Å, b = 8.5317(1) Å, c = 9.6945(2) Å, and β = 96.85(1) • . The preferential occupancy of Re over the 4g, 4i 3 and 4i 4 crystallographic sites were determined successfully by Rietveld refinement of XRD data, which is basically attributed to the effect of size. The compound exhibits planar magnetocrystalline anisotropy perpendicular to the [204] direction. The Curie temperature T C , the saturation moment M S and the magnetocrystalline anisotropy field H A are derived to be 467 K, 35.1 µ B f.u. −1 and 69.4 kOe, respectively.

A novel compound Nd3Fe26.5Re2.5 was synthesized. The structure and magnetic properties of the compound were investigated by means of x-ray powder diffraction (XRD) analysis and magnetic measurements. Nd3Fe26.5Re2.5 crystallizes in a monoclinic Nd3(Fe, Ti)29 structure with space group A2/m. The lattice constants of Nd3Fe26.5Re2.5 are a = 10.6131(1) Å, b = 8.5897(1) Å, c = 9.7518(1) Å, and β = 96.69(4)°, respectively. Rietveld refinement of the XRD data reveals that the Re atoms have a strong preference to occupy the three dumb-bell 4g, 4i3, and 4i4 sites. The preferential occupancy of the Re is predominantly determined by the atomic size effect. The final refined stoichiometry Nd3Fe26.65Re2.35 is in good agreement with the result of chemical analysis: Nd3Fe26.6(1)Re2.39(3). Nd3Fe26.5Re2.5 is found to be of planar anisotropy perpendicular to the [204] direction at room temperature. The Curie temperature TC, saturation magnetization MS, and magnetocrystalline anisotropy field HA are 354 K, 52.9 µB/f.u., and 20.6 T, respectively. The relatively low TC is related to the preferential occupations of the Re of the 4g, 4i3, and 4i4 sites. The temperature-dependent XRD experiment shows a contraction of the unit-cell volume with temperature around TC, which can be ascribed to the vanishing magnetism. The magnetism has a significant effect on the lattice parameters a, b, c, and β, which is anisotropic in character.