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Abstract:
Synthetic crystals of the ferberite FeWO4 have been grown by the chemical transport reaction starting from a polycrystalline sample of this phase. Magnetic susceptibility measurements showed an antiferromagnetic Neel temperature of T-N = 75 K. The anisotropy in the magnetic susceptibility can be ascribed to the magnetocrystalline anisotropy of the Fe2+ ion, the oxidation state of which was confirmed by X-ray absorption spectroscopy. While X-ray photoemission analysis indicated that all W ions are in the expected 6+ charge state, the dielectric permittivity of the FeWO4 crystals was found to be leaky, hindering changes at T-N to be detected. Subsequent thermoelectric power measurements suggested the presence of about 1.5% Fe3+. X-ray diffraction experiments confirmed the basic crystal structure of the wolframite type and revealed some structural disorder in the 1% range. Transmission electron microscopy allowed us to unveil the occurrence of stacking faults attributed to the similarity of the atomic environment of the Fe and W species.
