452 research outputs found
Comprehensive Demonstration of Spin-Hall Hanle Effects in Epitaxial Pt Thin Films
We demonstrate a nonlinear Hall effect due to the boundary spin accumulation
in Pt films grown on Al2O3 substrates. This Hall effect and the previously
demonstrated Hanle magnetoresistance provide a complete picture of the
spin-precession control of the spin and charge transport at the boundary of a
spin-orbit coupled material, which we refer to as spin-Hall Hanle effects
(SHHE). We also show that the SHHE can be employed to measure the spin
diffusion length, the spin-Hall angle, and the spin relaxation time of heavy
metal without the need of magnetic interface or the input from other
measurements. The comprehensive demonstration of SHHE in such a simple system
suggests they may be ubiquitous and needs to be considered for unravelling the
spin and charge transport in more complex thin film structures of spin-orbit
coupled materials
Inertial convection in a rotating narrow annulus: Asymptotic theory and numerical simulation
The following article appeared in Physics of Fluids, 2015, Volume 27, and may be found at http://scitation.aip.org/content/aip/journal/pof2/27/10/10.1063/1.4934527.An important way of breaking the rotational constraint in rotating convection is to invoke fast oscillation through strong inertial effects which, referring to as inertial convection, is physically realizable when the Prandtl number Pr of rotating fluids is sufficiently small.We investigate, via both analytical and numerical methods, inertial convection in a Boussinesq fluid contained in a narrow annulus rotating rapidly about a vertical symmetry axis and uniformly heated from below, which can be approximately realizable in laboratory experiments [R. P. Davies-Jones and P. A. Gilman, “Convection in a rotating annulus uniformly heated from below,” J. Fluid Mech. 46, 65-81 (1971)]. On the basis of an assumption that inertial convection at leading order is represented by a thermal inertial wave propagating in either prograde or retrograde direction and that buoyancy forces appear at the next order to maintain the wave against the effect of viscous damping, we derive an analytical solution that describes the onset of inertial convection with the non-slip velocity boundary condition. It is found that there always exist two oppositely traveling thermal inertial waves, sustained by convection, that have the same azimuthal wavenumber, the same size of the frequency, and the same critical Rayleigh number but different spatial structure. Linear numerical analysis using a Galerkin spectral method is also carried out, showing a quantitative agreement between the analytical and numerical solutions when the Ekman number is sufficiently small. Nonlinear properties of inertial convection are investigated through direct three-dimensional numerical simulation using a finite-difference method with the Chorin-type projection scheme, concentrating on the liquid metal gallium with the Prandtl number Pr = 0.023. It is found that the interaction of the two counter-traveling thermal inertial waves leads to a timedependent, spatially complicated, oscillatory convection even in the vicinity of the onset of inertial convection. The nonlinear properties are analyzed via making use of the mathematical completeness of inertial wave modes in a rotating narrow annulus, suggesting that the laminar to weakly turbulent transition is mainly caused by the nonlinear interaction of several inertial wave modes that are excited and maintained by thermal convection at moderately supercritical Rayleigh numbers.Leverhulme TrustMacau FDCTChinese Academy of Science
Giant interfacial spin-Hall angle from Rashba-Edelstein effect revealed by the spin-Hall Hanle processes
The Rashba-Edelstein effect (REE), which generates interfacial spin
polarization and subsequent spin current, is a compelling spin-charge
conversion mechanism for spintronics applications, since it is not limited by
the elemental spin-orbit coupling. In this work, we demonstrate REE at
Pt/ferroelectric interfaces using the recently elucidated spin-Hall Hanle
effects (SHHE), in which a Larmor precession of spin polarization in a
diffusion process from the interface manifest as magnetoresistance and Hall
effect. We show that REE leads to a three-fold enhancement of the effective
spin Hall angle in ferroelectric interface Pt/h-LuFeO3 compared to that of Pt
/Al2O3, although the difference in the spin relaxation time is negligible.
Modeling using SHHEs involving REE as an additional source of interfacial
polarization suggests that REE can lead to an interfacial spin Hall angle
(~0.3) that is one order of magnitude larger than the bulk value of Pt. Our
results demonstrate that a ferroelectric interface can produce large
spin-charge conversion and that SHHEs are a sensitive tool for characterizing
interfacial spin transport properties
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