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

Platunov, M. S.; Kazak, N. V.; Knyazev, Yu. V.; Bezmaternykh, L. N.; Moshkina, E. M.; Trigub, A. L.; Veligzhanin, A. A.; Zubavichus, Y. V.; Solovyov, L. A.; Velikanov, D. A.; Ovchinnikov, S. G. JOURNAL OF CRYSTAL GROWTH, 475 239-246; 10.1016/j.jcrysgro.2017.06.026 OCT 1 2017

Single crystalline Mn_2-xFe_xBO₄ 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. P_nam). 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 T_SG = 11, 14 and 18 K for x = 0.3, 0.5 and 0.7, respectively.