Crystal Structure of Paramagnetic DyMn2O5 at 298°K

Abstract

Paramagnetic DyMn2O5crystallizes in the orthorhombic system with lattice constantsa=7.2940±0.0008, b=8.5551±0.0008, and c=5.6875±0.0008 Å, in the space group Pbam(D 2h 9). There are four DyMn2O5 per unit cell. The crystal structure was solved by a combination of three‐dimensional Patterson and Fourier series and refined by the method of least squares. The integrated intensities of 5094 reflections were measured by PEXRAD, with 976 symmetry‐independent structure factors significantly above background. The final agreement factor between measured and calculated structure factors is 0.0401. There are two independent Mn atoms. One is pentacoordinated, with a slightly distorted tetragonal pyramidal configuration: two basal Mn–O distances are 1.926±0.006 Å, the other two are 1.911±0.005 Å, and the apical Mn–O bond, nearly normal to the basal plane, is 2.020±0.005 Å. The other Mn occupies a slightly compressed octahedron, with four planar Mn–O bonds of 1.940±0.004 Å and two, normal to this plane, of 1.873±0.004 Å. The octahedral Mn environment closely resembles that in β‐MnO2. The Dy is surrounded by a somewhat distorted square‐antiprismatic polyhedron of oxygen atoms, the Dy–O distance ranging from 2.341±0.005 to 2.469±0.005 Å, the average being 2.390 Å. The thermal vibrations are significantly anisotropic. The room‐temperature paramagnetism could mask an antiferromagnetic ordering of the octahedral Mn atoms.