Search results for "Spin relaxation"

Magnetic resonance imaging in primary cerebral neuroblastoma

1989

Reorientations and translations in a fragile glass-former: magnetic resonance studies of meta-fluoroaniline

1999

Abstract The rotational dynamics in supercooled liquid and glassy meta-fluoroaniline was studied using proton and fluorine spin-lattice relaxation times. It is shown that while proton relaxation is dominated by homonuclear relaxation, for fluorine heteronuclear relaxation prevails. The results could be well described using a distribution of correlation times. The mean correlation times show pronounced deviations from the simple Arrhenius law. In addition translational self-diffusion coefficients were measured for T>200 K using a static magnetic field gradient technique.

Characterization of water mobility in dry and wetted roasted coffee using low-field proton nuclear magnetic resonance

2007

Abstract Roasted and ground coffee was studied by low-field 1 H nuclear magnetic resonance at various water contents and temperatures. The spin–spin relaxation times ( T 2 ) were measured with single pulse free induction decay (FID) and Carr–Purcell–Meiboom–Gill (CPMG) sequences. Four relaxing components were distinguished: the solid population was observed with FID sequence at T 2s ∼9 μs; the other three populations, measured with the CPMG sequence, corresponded to an apolar phase, the coffee oil, and two polar phases. The two polar populations, observed at T 2m ∼6 ms and ∼27 ms (for coffee with 50% water content at 90 °C) were attributed to water in cell wall polymers and in water filling…

Temperature dependence of spin depolarization of drifting electrons in n-type GaAs bulks

2010

The influence of temperature and transport conditions on the electron spin relaxation in lightly doped n-type GaAs semiconductors is investigated. A Monte Carlo approach is used to simulate electron transport, including the evolution of spin polarization and relaxation, by taking into account intravalley and intervalley scattering phenomena of the hot electrons in the medium. Spin relaxation lengths and times are computed through the D'yakonov-Perel process, which is the more relevant spin relaxation mechanism in the regime of interest (10 < T < 300 K). The decay of the initial spin polarization of the conduction electrons is calculated as a function of the distance in the presence of…

High-field nuclear spin relaxation in liquids and solids

1990

The authors generalise the standard theory of nuclear spin relaxation to situations in which the Markovian approximation is not applicable. Expressions for generalised frequency-dependent spin relaxation functions are presented. They show that under high-field conditions the relaxation of longitudinal magnetisation is exponential independent of the particular time dependence of the correlation functions.

EFFECT OF A FLUCTUATING ELECTRIC FIELD ON ELECTRON SPIN DEPHASING TIME IN III–V SEMICONDUCTORS

2012

We investigate the electron spin dephasing in low n-doped GaAs semiconductor bulks driven by a correlated fluctuating electric field. The electron dynamics is simulated by a Monte Carlo procedure which keeps into account all the possible scattering phenomena of the hot electrons in the medium and includes the evolution of spin polarization. Spin relaxation times are computed through the D’yakonov–Perel process, which is the only relevant relaxation mechanism in zinc-blende semiconductors. The decay of initial spin polarization of conduction electrons is calculated for different values of field strength, noise intensity and noise correlation time. For values of noise correlation time compara…

New insights into electron spin dynamics in the presence of correlated noise

2011

The changes of the spin depolarization length in zinc-blende semiconductors when an external component of correlated noise is added to a static driving electric field are analyzed for different values of field strength, noise amplitude and correlation time. Electron dynamics is simulated by a Monte Carlo procedure which keeps into account all the possible scattering phenomena of the hot electrons in the medium and includes the evolution of spin polarization. Spin depolarization is studied by examinating the decay of the initial spin polarization of the conduction electrons through the D'yakonov-Perel process, the only relevant relaxation mechanism in III-V crystals. Our results show that, f…

Supercurrent Induced Charge-Spin Conversion in Spin-Split Superconductors

2017

We study spin-polarized quasiparticle transport in a mesoscopic superconductor with a spin- splitting field in the presence of co-flowing supercurrent. In such a system, the nonequilibrium state is characterized by charge, spin, energy and spin energy modes. Here we show that in the presence of both spin splitting and supercurrent, all these modes are mutually coupled. As a result, the supercurrent can convert charge imbalance, that in the presence of spin splitting decays on a relatively short scale, to a long-range spin accumulation decaying only via inelastic scattering. This effect enables coherent charge-spin conversion controllable by a magnetic flux, and it can be detected by studyin…

Effect of a fluctuating electric field on electron spin dephasing in III-V semiconductors

2011

In the present work we investigate electron spin relaxation in low-doped n-type GaAs semiconductor bulks driven by a static electric field. The electron dynamics is simulated by a Monte Carlo procedure which keeps into account all the possible scattering phenomena of the hot electrons in the medium and includes the evolution of spin polarization. Spin relaxation lengths are computed through the D’yakonov-Perel process, which is the only relevant relaxation mechanism in zinc-blende semiconductors. Since semiconductor based devices are always imbedded into a noisy environment that can strongly affect their performance, the decay of initial spin polarization of conduction electrons is calculat…

RELAXATION OF ELECTRON SPIN DURING FIELD TRANSPORT IN GaAs BULKS

2011

The spin depolarization of drifting electrons in a n-type doped GaAs bulk semiconductor is studied, in a wide range of lattice temperature (40 K < TL < 300 K) and doping density (10^{13} cm^{−3} < n < 10^{16} cm^{−3}), by adopting a semiclassical Monte Carlo approach. The effect of the mechanism of Dyakonov-Perel (DP) on the spin depolarization of the conduction electrons is analyzed as a function of the amplitude of a static electric field, ranging between 0.1 and 6 kV cm^{−1}, by considering the spin dynamics of electrons in both the Γ-valley and the upper L-valleys of the semiconductor. Moreover, the role of the electron-electron scattering mechanism in the suppression of DP spin relaxat…