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

• Published in: Journal of magnetism and magnetic materials Vol. 498; p. 166208
• Main Authors: Ivantsov, R., Ivanova, O., Zharkov, S., Molokeev, M., Krylov, A., Gudim, I., Edelman, I.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-03-2020; Elsevier BV
• Subjects: Antiferromagnetism; Dichroism; Ellipsometric parameters; Excitons; Filing; Hematite; Inflection points; Iron oxides; Line shape; Magnetic circular dichroism; Magnetic moments; Magnons; Nanocrystals; Nanoparticles; Neel temperature; One-ion d-d transitions; Optical absorption; Pare exciton-magnon transitions; Raman scattering; Single crystals; α-Fe2O3; Hematite; Pare exciton-magnon transitions; Ellipsometric parameters; Raman scattering; α-Fe2O3; Magnetic circular dichroism; One-ion d-d transitions; Optical absorption
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2019.166208

•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.