  Single crystalline MgFeBO_4, Mg_0.5Co_0.5FeBO_4 and CoFeBO_4 have been grown
by the flux method. The samples have been characterized by X-ray spectral
analysis, X-ray diffraction and X-ray absorption spectroscopy. The X-ray
absorption near-edge structure (XANES) and extended X-ray absorption fine
structure (EXAFS) spectra have been measured at the Fe andCoK-edges over a wide
temperature range (6.5 - 300 K). The composition, the charge state and local
environment of both Fe and Co atoms have been determined. The effects of Mg
substitution by Co on the local structural distortions have been revealed
experimentally and the M-O bond anisotropy has been found.
