Andrey A. Kozlov

Magnetorefractive effect in magnetic nanocomposites

The magnetorefractive effect in ferromagnetic metal-insulator granular nanostructures (CoFeZr)-SiOn, Co-Al-O, FeSiOn, and (CoFe)-(Mg-F) is investigated in the infrared spectral region in a wavelength range from 5 to 20 μm. The magnitude of the effect varies from 0.1 to 1.5% for different nanocomposites and strongly depends on the frequency of light and magnetoresistance. It is shown that the reflection coefficient changes in a magnetic field not only due to the magnetorefractive effect, but also due to the even magnetooptical effect. Simple relations describing this effect are given for the case when the reflection from the substrate is insignificant and in the case of a three-layer (insulator-film-substrate) system. The expression for the frequency dependence of the magnetorefractive effect in nanocomposites is derived and its features in the case of high-frequency spin-dependent tunneling are analyzed.

Synthesis and characterization of difluoromethylene-homo[60]fullerene, C60(CF2)

Refluxing of the o-DCB solution of C60 with CF2ClCOONa and 18-crown-6 leads to formation of C60(CF2)n (n = 1-3); the monoadduct C60(CF2) has been found to consist of the main [6,6]- and minor [5,6]-isomers, both having an open structure.

Magnetorefractive Effect in Granular Alloys with Tunneling Magnetoresistance

The magnetorefractive effect and optical reflectivity are studied in granular Co-Al-O, Co-Si-O, and Co-Ti-O metal-insulator alloys exhibiting tunneling magnetoresistance for compositions close to the percolation threshold. The dependences of these effects on frequency, angle of incidence, and light polarization were measured. The experimental data obtained suggest that the major MRE mechanism in these systems is spin-dependent tunneling at optical frequencies.

Microwave-frequency spin-dependent tunneling in nanocomposites

The transmission coefficient of films of Co51.5Al19.5O29, Co50.2Ti9.1O40.7, Co52.3Si12.2O35.5, and (Co0.4Fe0.6)48(MgF)52 ferromagnetic metal-insulator magnetic nanocomposites exhibiting tunneling magnetoresistance and the magnetorefractive effect for electromagnetic waves was studied in the frequency range 30–50 GHz. The transmission coefficient of the first two compositions varies strongly under an applied magnetic field, and its variation exhibits a linear correlation with the field dependence of magnetoresistance. For the other two compositions, the transmission coefficient does not depend on magnetic field. The data obtained are interpreted in terms of the concept of microwave spin-dependent tunneling.

Giant magnetorefractive effect in magnetic granular CoFe-MgF alloys

This paper reports on an IR study (5–20 µm) of the dispersion and field dependences of the magnetorefractive effect in granular CoFe-MgF (metal-insulator) systems, which exhibit, in compositions close to the percolation threshold, a tunneling magnetoresistance of 7.5% in a field of 1700 Oe. The change in the reflectivity of p-polarized light under magnetization in the IR spectral region 5–7 µm is of the order of 0.1%, while in the 10-to 12-µm region, this change, reaches record-high values of 1.2–1.5%, which exceed the usual odd and even magnetooptic reflectivities in the IR range by two orders of magnitude. The magnetorefractive effect in magnetic systems with tunneling conduction originates from spin-dependent high-frequency tunneling.

Novel possibilities in the study of isolated carbon nanotubes

We report the first detection of carbon nanotubes in the gas phase in a matrix-assisted laser desorption/ionization (MALDI) mass spectrometric experiment. These observations open the possibility of studying isolated nanotubes in the gas phase by means of various spectroscopic methods and a possible way to separate them.

Preparation and structures of [6,6]-open difluoromethylene[60]fullerenes: C60(CF2) and C60(CF2)2.

Difluoromethylenation of C60 with thermally decomposed CF2ClCO2Na provides novel C60(CF2) and C60(CF2)2 compounds with unique [6,6]-open structures. A theoretical survey of CF2 derivatives of C60 demonstrates that carbon cage opening can be controlled via charging of the molecule and that the thermodynamically preferable structures combine the trend to form open isomers with the compactness of the addition motifs, which results in the formation of windows in the fullerene cage.

Magnetorefractive effect in nanogranular films (CoFe)-(Mg-F)

In this paper, we describe the magnetorefractive effect in nanocomposites (CoFe)-(Mg-F) in the infrared wavelength range 5-20 /spl mu/m.

Magnetorefractive Effect in Magnetic Nanocomposites in Reflection: Dependencies on Incident Angle and Polarization of Light

We calculate the magnetorefractive effect in ferromagnetic metal-insulator nanocomposites in reflection as a function of an incident angle for p- and s-polarization of light. The MRE is larger for p-polarized light and attains the maximum value for the incident angle o 0 close to the Bruster angle. The difference between the MRE for p-and s-polarized light when 300<o 0<700 is noticeable, but not well pronounced for metallic samples, and by contrast, can be very large in insulating samples. The available experimental data on angular and polarization dependencies of the MRE in various nanocomposites are analyzed.