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- Quantum spin polarization effect in multi-nanolayer structuresPublication . Makarov, Vladimir I.; Khmelinskii, IgorWe studied the spin-polarized state transport in Fe-SnO2-Ag and Fe-BeO-Ag three-nanolayer sandwich structures. The exchange-resonance spectra of these sandwich structures are quite specific and different from those observed earlier in other three-nanolayer structures. The presently recorded spectra comprise a set of discrete lines, their width increasing with the sample temperature and also with the Ag layer thickness, for both samples. The linewidth dependences on temperature and Ag layer thickness were studied in detail. The effect of thickness of the intermediate nanolayers of SnO2 and BeO on the linewidth was also explored. To explain the observed line broadening effects, we proposed and developed the spin-orbit (SO) coupling mechanism of the electron spin relaxation. In the frameworks of this mechanism, we assumed that the electron spin of a bonding electron in one of the layers of the sandwich system is coupled by SO interaction with the other layers. We found that the change in phonon densities affects the linewidths of the exchange resonance spectra. We estimated the values of the model parameters from the analysis of the experimental data. To that end, we continue further development of our earlier theoretical model, using it to interpret the current experimental results, including ab initio calculations of the electronic structure. The exchange resonance spectra were simulated using phenomenological model, where the anisotropy of the g-factor was introduced. We performed ab initio simulations of the exchange resonance spectra and their linewidths, using Gaussian-2000 and a homemade FORTRAN code.
- Quantum confinement in multi-nanolayer sandwich systemsPublication . Khmelinskii, Igor; Makarov, Vladimir I.Presently we explored quantum confinement (QC) in three-nanolayer sandwich systems, composed of Au-SnO2-Fe, Au-SnO2-Si and Au-SnO2-Ag layers. We recorded the absorption spectra of these sandwich systems, all with discrete structure. We recorded the action spectra of the photocurrent for the Au-SnO2-Fe sandwich system, with the photocurrent quantum yields increasing with the photon energy, achieving 3.1 at 4.7 x 10(4) cm(-1). The photocurrent action spectra correlate with high accuracy with optical absorption spectra. We discuss the mechanisms determining the absorption bandwidth value, including surface imperfections, thermal distribution of the vibrational level populations in the electronic ground state, and the diabatic coupling of levels of the excited state to those of a "dark" state. Volt-Ampere (V/A) characteristics were recorded for all three of the sandwich systems, quite similar to those of a Schottky diode. We report the parameter values of the V/A characteristics, found by fitting the experimental data with a theoretical curve. We also report charge density changes in the SnO2 layer caused by low constant voltage applied to the sandwich structure, observed as changes in the absorption band intensity.
- Macroscopic excitation energy transport in a structured Co nanolayerPublication . Khmelinskii, Igor; Makarov, Vladimir I.We report absorption spectra of the 7.3-and 11.3-nm Co nanolayers and emission of a structured Co nanolayer. The structure contains a 7.3-nm Co nanolayer covering a 25 x 25 mm(2) fused silica substrate, with a thicker 11.3-nm Co track in the middle of the substrate. We report that the radiation energy absorbed by the entire Co nanolayer is transferred to the thicker nanotrack. The transferred energy is reemitted by the track, with the emission spectra containing well-defined emission bands, strongly dependent on the excitation wavelength. We report that the bands appearing in the emission spectra of the nanotrack correspond to the transitions from the higher electronic excited states of the nanotrack to its first excited state. We therefore identify the observed emission as the superemission of the Co nanotrack. The superemission quantum yield is dependent on the excitation wavelength, decreasing at higher excitation energies. We propose a theoretical model that explains the results obtained. The model analysis produced estimates of several model parameters.