Magnetic properties of mixed spinel ferrites are determined, in great extent, by the magnetic cation distribution among tetrahedral and octahedral positions in a crystal. In the case of CoZn-ferrites, most researchers reported a predominant localization of the divalent cobalt ions in octahedral positions. Using the citrate precursor auto-combustion method, we successfully synthesized CoxZn1-xFe2O4 nanoparticles (x changed from 0.0 to 0.5) with an approximately evenly distribution of Co2+ ions between these interstitial positions. Fe3+ ions are localized preferably in octahedral positions. This type of 3d-ion distribution predetermined the combination of the large saturation magnetization and very low coercive field of the nanoparticles, which may be of importance for applications. MCD spectra of CoxZn1-xFe2O4 nanoparticles are studied here for the first time. Revealed intense MCD peak at 1.75 eV corresponds to the emission wavelength (710 nm) of some lasers, e.g., ALP-710 nm (NKT Photonics, Denmark) which may be of interest for photonic devices.

Magnetic circular dichroism (MCD) spectroscopy for manganite films of various compositions and morphologies has been studied in the range of 1.2-3.7 eV. The primary focus was on the temperature behavior of the MCD spectra, as well as the magnetization and resistivity of the films. The data obtained were analyzed in comparison with magneto-optical spectroscopy of the Kerr rotation (KR) on both single crystal and thin film of manganites. It has been established that the MCD response at 2.3 eV is typical for manganites transitioning into a conducting state. Consequently, it reflects a change in the band structure of the material. This response is also observed in the KR spectrum of manganites in the range 2.3-2.6 eV below the metal-insulator transition temperature. These findings complement the understanding of the electronic structure of manganites in general. Moreover, they also provide a basis for the search for new functional materials.

Magnetic circular dichroism (MCD) spectroscopy was used to study the features of the electronic structure of an epitaxial La0.7Ca0.3MnO3 film in the range of 1.2 - 4 eV. The study of the temperature behavior of the MCD spectra made it possible to establish a correlation between the magnetooptical and transport properties of the sample. The data obtained were analyzed in comparison with MCD data for polycrystalline manganite films of various RE1-xAxMnO3 compositions. The MCD spectra of the films were compared with the spectra of the off-diagonal component of the permittivity tensor calculated from the data of the magneto-optical Kerr effect for films of the same composition. A unified set of ground and excited electronic states characteristic of RE1-xAxMnO3 manganites in the visible and near infrared ranges has been identified. These results are important for a qualitative theoretical description of the electronic structure of strongly correlated magnetic oxides.

Mixing rules may be extremely useful for predicting the properties of composite materials and coatings. The paper is devoted to the study of the applicability of the mixing rules to permittivity and permeability and the possibility of retrieving the intrinsic properties of inclusions. Magnetically soft Ni-Zn ferrites are chosen as the object of the study due to their low permittivity and the negligible influence of the skin effect. Due to this, the microwave properties of bulk ferrites may be measured by standard techniques. It is suggested to perform the analysis of the microwave properties of composites filled with Ni-Zn ferrite powder in terms of the normalized inverse susceptibility defined as the volume fraction of inclusions divided by the effective dielectric or magnetic susceptibility of the composite. The measured properties of the bulk ferrite are compared with those obtained by mixing rules from composite materials. The experimental evidence for difference between the mixing rules for permittivity and permeability of a composite, which was previously predicted only theoretically, is obtained. The reason for the difference is considered to be the effect of non-ideal electrical contacts between neighboring inclusions. It is also experimentally shown that the measured permeability of the bulk material may differ from the retrieved one. The measured static permeability is 1400 and the retrieved one is 12. The reason for the discrepancy is the difference between the domain structures and demagnetizing fields of particles and bulk ferrite.

Magnetic and magneto-optical properties of cobalt nanoparticles (Co-NPs) dispersed in a transparent dielectric SiO2 and semiconductor ZnO matrices have been investigated. Field and temperature dependences of the samples magnetization showed the typical behavior of an ensemble of superparamagnetic particles with a blocking temperature near and below room temperature. The spectroscopy of magnetic circular dichroism (MCD) in the visible and near-infrared light ranges has revealed a significant difference between the behavior of the Co-NPs and a solid Co film. It has been found that the MCD spectrum shape for the Co-NPs does not depend on the matrix type. The room temperature magneto-optical activity of the Co-NPs in the different matrices has been estimated as an indicator for practical applications.

Tuning optical or magnetic properties of nanoparticles, by addition of impurities, for specific applications is usually achieved at the cost of band gap and work function reduction. Additionally, conventional strategies to develop nanoparticles with a large band gap also encounter problems of phase separation and poor crystallinity at high alloying degree. Addressing the aforementioned trade-offs, here we report Ni-Zn nanoferrites with energy band gap (Eg) of ≈3.20 eV and a work function of ≈5.88 eV. While changes in the magnetoplasmonic properties of the Ni-Zn ferrite were successfully achieved with the incorporation of bismuth ions at different concentrations, there was no alteration of the band gap and work function in the developed Ni-Zn ferrite. This suggests that with the addition of minute impurities to ferrites, independent of their changes in the band gap and work function, one can tune their magnetic and optical properties, which is desired in a wide range of applications such as nanobiosensing, nanoparticle based catalysis, and renewable energy generation using nanotechnology.

Morphology, structure, magnetic properties and magnetic circular dichroism (MCD) were studied for the FexSy and FexSey nanoparticles (NPs) synthesized with the polyol mediated and the thermal decomposition processes, correspondingly, at different regimes. For all NPs samples, but Fe3S4, MCD was measured for the first time. It has been shown that in the case of sulfides, the character of the MCD spectrum changes as the NPs phase composition transforms from Fe3S4 to FeS with the synthesis temperature increase. At the same time, the shape of the MCD spectrum is almost independent of the NPs phase in the case of iron selenides

Spray pyrolysis of an aqueous solution of iron nitrate, proceeded with reduction of the product in hydrogen, gave iron powder with micron-sized hollow particles. Coating these iron particles with SiO2 through tetraethyl orthosilicate hydrolysis prevented interparticle electrical contacts and suppressed DC percolation. This material shows a high ferromagnetic resonance frequency of 18 GHz, low permittivity, and weighs 20% less than common carbonyl iron. Potential microwave applications are for inductors and electromagnetic interference shielding designs.