Magnetic circular dichroism in the canted antiferromagnet α-Fe2O3: Bulk single crystal and nanocrystals

•MCD, FR and optical absorption spectra were obtained in the transmitted light for α-Fe2O3 nanocrystals.•Ellipsometric parameters were obtained in the reflected light for the α-Fe2O3 single crystal.•Very strong S-shape line in the MCD spectrum near 2.0–2.5 eV distinguishes hematite from other iron oxides.•MCD features in the interval 1.2–4 eV are associated with one-ion d-d and pare exciton-magnon transitions. Hematite, α-Fe2O3, is a canted antiferromagnet with the Neel temperature of 960 K. The Morin transition, which occurs when the temperature is lowered to ~260 K, when the magnetic moments of the sublattices become strictly antiparallel to each other and the resulting magnetic moment disappears, is a characteristic feature of this compound. Detailed investigations are presented here of the magneto-optical effects in the α-Fe2O3 nanoparticles in the transmitted light and in the α-Fe2O3 single crystal in the reflected light. Two types of magneto-optic features were revealed in the magnetic circular dichroism (MCD) spectrum. Some of them described by the Gauss line shape were associated with one-ion d-d transitions. Others were described by the S-shaped line with the inflection points corresponding to the absorption maxima. Last features were assigned to the pair exciton-magnon transitions. An exceptionally strong S-shaped line at 2.0–2.5 eV appeared to be a unique feature of α-Fe2O3 distinguishing it from other iron oxide compounds. The origin of the high effectiveness of the pair exciton-magnon interaction giving rise to this strong S-shaped feature in the MCD spectrum of α-Fe2O3 is discussed.