G. S. Krinchik

Magneto-optical properties of new manganese oxide compounds

Abstract The investigation of magneto-optical properties of manganese magnetic oxide compounds containing (MnO6)9- and (MnO6)8- octahedral magnetoactive complexes — perovskites, orthomanganites, pyrochlores and ilmenites — and influence of Bi3+ and Pb2+ ions on their magneto-optical activity (MOA) was carried out in the energy range of 1.5–4.5 eV. MOA of investigated compounds was shown to be defined by the transitions in (MnO6)9- and (MnO6)8- complexes, the frequencies of these transitions were determined. The strong increase of MOA at the energies 4–4.5 eV in compounds containing both Bi3+ (or Pb2+) and Mn4+ ions was observed. The enhancement of charge-transfer transitions contribution to MOA due to the admixture of Bi3+(Pb2+) ions (6p)-wave functions to the molecular orbitals of (MnO6)8- complexes is considered to be the most likely mechanism of this phenomenon.

Near-surface magnetic structures in iron borate

Abstract Surface magnetism on natural non-basal faces of iron borate monocrystals was found and analysed by means of the magneto-optical and Bitter methods. The surface magnetism here is represented by a macroscopical transition magnetic layer, the result of surface magnetic anisotropy. Anisotropy is caused by the change in surface magnetic ion environment symmetry. The erasure of surface magnetism at a face of the (10 1 4)-type takes place in a field of H c = 1.6 kOe, the same characteristic for faces of the (11 1 0) and (11 2 3)-types is ⪅ 100 Oe. By measuring the temperature-critical field relationship in the temperature range from 77 K upto the Neel point, it was found that H c is proportional to the crystals magnetization. Surface anisotropy energy and the structure of transition magnetic layers are calculated for the analyzed types of faces. The developed theory gives a correct description of surface magnetic anisotropys symmetry, yields the H c field value order which agrees with the experimentally determined one, and also explains the temperature-critical field relationship.

Magnetic dichroism and anisotropy of exchange interaction in ytterbium iron garnet

Abstract Anisotropy of magnetic linear and circular dichroism in the region of the 2 F 7 2 - 2 F 5 2 absorption band of the Yb 3+ ion is investigated experimentally and theoretically when magnetizing along main crystallographic directions of ytterbium iron garnet in the temperature interval 50–150 K. The Judd-Ofelt approximation is proved to be valid for calculation of oscillator strengths of the transitions between individual Stark levels for the Yb 3+ ion. Parameters which determine the intensities of polarized spectra for Yb 3+ ion are obtained when fitting experimental and theoretical spectra. Strongly anisotropic exchange splittings are determined within the crystal field model. Consideration of anisotropy of rare earth-iron exchange is essential for a description of the observed anisotropy of magnetic dichroism spectra. The intensities of polarized spectra are shown to be more sensitive than the exchange energy splittings to parameters of centrosymmetric crystal field.