Mossbauer magnetization and resistivity studies of Fe1.91V0.09BO4

Single crystals of Fe1.91V0.09BO4 were prepared by spontaneous crystallization using a solution melt technology for the first time and its structure, electronic and magnetic properties were investigated by X-ray diffraction, Mossbauer spectroscopy, magnetization and electrical measurements. Room-temperature Mossbauer measurements indicate that 'localized' (Fe2+, Fe3+) and 'delocalized' (Fe2.5+) states in ratio 0.31:0.345:0.345 distributed over two crystallographically non-equivalent positions exist. The results of magnetic measurements show that warwickite is a P-type ferrimagnet below T=130K. Resistivity measurements show a variable-range-hopping when electron-electron interactions cause a soft Coulomb gap in the density of states at the Fermi energy