57Fe NMR and exchange integrals in Al-substituted hematite

The room temperature NMR spectra of57Fe in hematite substituted by varying content of Al were measured and exchange integrals of the nearest four pairs Fe3+−Fe3+ were estimated: The values 261.9, −109.5, 146.6, 49.6 [10−22T2/J] for the first, second, third and fourth pair respectively were obtained.