Structure, magnetic properties, and magnetovolume effect of Nd3Fe26.5Re2.5

Abstract

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.