Papers by Keyword: Spin Relaxation

Abstract: Technical analysis of the performance optimization of nanospintronics devices based on carbonaceous materials has been presented in this paper. Mathematical formulation of the nanospintronics devices and a brief theory of these devices have been briefly discussed. A qualitative review of some of important nanospintronics based devices has also been given. The paper is expected to be useful to the new entrants in this exciting field, and also for the designers of some novel devices based on use of carbonaceous materials in nanospintronics.

Abstract: The results of investigation of changes in electronic structure and magnetic properties of multilayer graphene nanoclusters (nanographites) occurring during their interaction with adsorbed chlorine molecules are presented. The found reversible decrease in the density of states of current carriers D(E_F) at the Fermi energy E_F can be explained by the spin-splitting of edge π-electron states in nanographites induced by the enhancement of electron-electron interactions due to increase of the D(E_F) at partial transfer of the electron density from nanographites to chlorine adatoms. The revealed irreversible decrease in the concentration of localized spins indicates that the electron spins of 3p-orbitals of chlorine and unpaired (dundling) σ-orbitals of edge carbon atoms are coupled also at this interaction, i.e. the edge covalent compound of nanographite with chlorine forms. Character of changes in the spin-relaxation rate of π-electrons depending on the amount of adsorbed chlorine molecules and on temperature in chlorinated samples are also consistent with the above model of nanographite-chlorine interaction.

Abstract: The electron spin properties of semiconductors are of immense interest for their potential in spin-driven applications. Silicon is a perfect material for spintronics due to a long spin lifetime. Understanding the peculiarities of the subband structure and details of spin propagation in thin silicon films in the presence of the spin-orbit interaction is under scrutiny. We have performed simulations to obtain the surface roughness limited, acoustic-and optical-phonon mediated spin relaxation time, when the film is under shear strain. The degeneracy between the non-equivalent valleys is lifted by strain, which in turn subdues the dominating inter-valley relaxation components and increases the spin lifetime. We also elaborate on the injection orientation sensitive spin relaxation model and predict that the spin relaxation time is maximum, when the spin is injected in-plane, relative to the (001) oriented silicon film.

Abstract: Transport and spin relaxation characteristics of the conduction electrons in silicon samples doped with bismuth in the 1.1·10¹³ - 7.7·10¹⁵ cm^-3 concentration range were studied by the Hall and electron spin resonance spectroscopy. Hall effect measurements in the temperature range 10-80 K showed a deviation from the linear dependence of the Hall resistance in the magnetic field, which is a manifestation of the anomalous Hall effect. The magnetoresistance investigation shows that with current increasing magnetoresistance may change its sign from positive to negative, which is most clearly seen when the bismuth concentration goes up to 7.7·10¹⁵ cm^-3. The conduction electron spin relaxation rate dramatically increases in silicon samples with sufficiently low concentration of bismuth ~ 2·10¹⁴ cm^-3. All these results can be explained in terms of the concept of spin-dependent and spin flip scattering induced by heavy bismuth impurity centers.

Abstract: We used Magnetic Resonance microimaging (MRI) to study the compressive behaviour of synthetic elastin. Compression-induced changes in the elastin sample were quantified using longitudinal and transverse spin relaxation rates (R1 and R2, respectively). Spatially-resolved maps of each spin relaxation rate were obtained, allowing the heterogeneous texture of the sample to be observed with and without compression. Compression resulted in an increase of both the mean R1 and the mean R2, but most of this increase was due to sub-locations that exhibited relatively low R1 and R2 in the uncompressed state. This behaviour can be described by differential compression, where local domains in the hydrogel with a relatively low biopolymer content compress more than those with a relatively high biopolymer content.

Abstract: The dependence of electron spin relaxation on the carrier density are investigated based on the D’yakonov-Perel relaxation mechanism. Experimental results obtained by using femtosecond pump-probe technique in AlGaAs/GaAs multiple quantum wells at room temperature show that the spin relaxation time increases from 58 to 82ps at carrier density of 1×1017 to 1×1018cm－3 consistent with the theoretical prediction. This result reveals that with the increment of the carrier density, the spin orbit interaction reduces due to the more frequent momentum scattering and the spin relaxation time prolongs

Abstract: We review our recent experimental findings by optical orientation spectroscopy that show efficient spin relaxation within semiconductor spin detectors to be an important factor limiting efficiency of spin injection in spin light-emitting structures based on ZnCdSe/ZnMnSe and InGaN/GaMnN. We provide evidence for the physical mechanism responsible for the observed efficient spin relaxation that accompanies momentum and energy relaxation of excitons/carriers. These findings call for increasing efforts in suppressing spin relaxation in spin detectors.