Effect of Fe-substitution on the structure and magnetism of single crystals Mn2-xFexBO4

•Single crystals of of the warwickites Mn2-xFexBO4 (x=0.3, 0.5, 0.7) have been synthesized.•Crystal and local atomic structure has been studied through X-ray diffraction and X-ray absorption spectroscopy.•The Fe-doping was found to enhance the magnetic frustation giving rise to the supression of the long-range magnetic order. Single crystalline Mn2-xFexBO4 with x=0.3, 0.5, 0.7 grown by the flux method have been studied by means of X-ray diffraction and X-ray absorption spectroscopy at both Mn and Fe K edges. The compounds were found to crystallize in an orthorhombic warwickite structure (sp. gr. Pnam). The lattice parameters change linearly with x thus obeying the Vegard’s law. The Fe3+ substitution for Mn3+ has been deduced from the X-ray absorption near-edge structure (XANES) spectra. Two energy positions of the absorption edges have been observed in Mn K-edge XANES spectra indicating the presence of manganese in two different oxidation states. Extended X-ray absorption fine structure (EXAFS) analysis has shown the reduction of local structural distortions upon Fe substitution. The magnetization data have revealed a spin-glass transition at TSG=11, 14 and 18K for x=0.3, 0.5 and 0.7, respectively.