The crystal growth and properties of novel magnetic double molybdate RbFe5(MoO4)7 with mixed Fe3+/Fe2+ states and 1D negative thermal expansion

Single crystals of new compound RbFe5(MoO4)(7) were successfully grown by the flux method, and their crystal structure was determined using the X-ray single-crystal diffraction technique. The XRD analysis showed that the compound crystallizes in the monoclinic space group P2(1)/m, with unit cell parameters a = 6.8987(4), b = 21.2912(12) and c = 8.6833(5) angstrom, beta = 102.1896(18)degrees, V = 1246.66(12) angstrom(3), Z (molecule number in the unit cell) = 2, R-factor (reliability factor) = 0.0166, and T = 293(2) K. Raman spectra were collected on the single crystal to show the local symmetry of MoO4 tetrahedra, after the confirmation of crystal composition using energy dispersive X-ray spectroscopy (EDS). The polycrystalline samples were synthesized by a solid-state reaction in the Ar atmosphere; the particle size and thermal stability were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) analyses. The compound decomposes above 1073 K in an Ar atmosphere with the formation of Fe(iii) molybdate. The thermal expansion coefficient along the c direction has the value alpha = -1.3 ppm K-1 over the temperature range of 298-473 K. Magnetic measurements revealed two maxima in the magnetization below 20 K, and paramagnetic behavior above 50 K with the calculated paramagnetic moment of 12.7 mu B per formula unit is in good agreement with the presence of 3Fe(3+) and 2Fe(2+) in the high-spin (HS) state. The electronic structure of RbFe5(MoO4)(7) is comparatively evaluated using X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations.

Automated summary

Single crystals of the new compound RbFe5(MoO4)(7) were grown successfully by the flux method, and their crystal structure was determined using X-ray single-crystal diffraction technique. The compound crystallizes in a monoclinic space group, showing thermal stability and thermal decomposition behavior. Furthermore, characterization techniques like Raman spectroscopy, magnetic measurements, and electronic structure evaluation using XPS and DFT calculations were employed to study the compound.