The converse effects of spin photocurrent and current induced spin polarization are experimentally demonstrated in a two-dimensional electron gas system with Rashba spin splitting. Their consistency with the strength of the Rashba coupling as measured for the same system from beating of the Shubnikovde Haas oscillations reveals a unified picture for the spin photocurrent, current-induced spin-polarization, and spin-orbit coupling. In addition, the observed spectral inversion of the spin photocurrent indicates a system with dominating structure inversion asymmetry. DOI: 10.1103/PhysRevLett.96.186605 PACS numbers: 72.25.Fe, 72.25.Pn With the basic idea of the spin field effect transistor, as proposed by Datta and Das [1], the electric field tunable spin-orbit interaction has been an ideal candidate for manipulating the electron spin polarization. The structural inversion asymmetry (SIA) induced spin-orbit coupling (Rashba interaction [2]) in a two-dimensional electron gas (2DEG) system has attracted more and more attention due to its potential applications in spintronics devices. With spin splitting of the energy bands, optical excitation of quantum well (QW) structures by circularly polarized radiation will lead to a current whose direction and magnitude depend on the helicity of the incident light. This is named the circular photogalvanic effect (CPGE) and has been demonstrated using intersubband [3,4] or interband [5] excitations. A related effect, in which the current is driven by the spin-flip process of the nonequilibrium population of electrons in the spin-split bands, is called the spingalvanic effect [6]. The most interesting consequence of the k-dependent spin splitting is the implication that an applied electric field would induce not only a charge current but also a spin polarization [7][8][9][10][11][12][13] along the direction perpendicular to the current.This Letter provides the experimental evidence of circularly polarized optical-excitation-induced spin photocurrent in (001) grown InGaAs=InAlAs 2DEGs under oblique incidence of radiation for interband excitation, which is 2 orders of magnitude stronger than similar observations using far-infrared excitation for intersubband transitions. The current-induced spin polarization in the same samples is measured using the Kerr rotation experiment. These results are consistent with the spin splitting of the energy bands as examined by the beating of the Shubnikovde Haas (SdH) oscillations. The correlation in these experiments with great consistency reveals a unified picture for the spin photocurrent, current-induced spin-polarization and spin-orbit coupling. Furthermore, the theoretically predicted spectral inversion of the CPGE spin photocurrent is experimentally observed.Two samples (named D and E) studied here were In x Ga 1ÿx As=In 0:52 Al 0:48 As 2DEGs grown on a semiinsulating (001) InP substrate with well thickness of 14 nm. The SIA was achieved by doping of only one side of the barrier layer (on top of the well). To enhance the SIA, sample E wa...

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Perovskite type ͑Ba 0.9 Bi 0.1 ͒͑Ti 0.9 Al 0.1 ͒O 3 ͑BBTA͒ ceramics have been prepared through solid state reaction route. The room temperature x-ray diffraction study suggests that BBTA ceramics have single phase tetragonal symmetry with space group P4mm. In contrast to the sharp dielectric transition of pure BaTiO 3 , a broad dielectric anomaly coupled with the shift in dielectric maxima toward a higher temperature with increasing frequency has been observed in BBTA. The quantitative characterization based on empirical parameters ͑⌬T m , ␥, ⌬T relax , and ⌬T diffuse͑1 kHz͒ ͒ confirms its relaxor nature. The dielectric relaxation which follows the Vogel-Fulcher relationship with E ␣ = 0.011 eV, T f = 356 K, and f 0 = 1.38ϫ 10 10 Hz, further supports spin-glass-like characteristics. In this system, the relaxor behavior can be attributed to the dynamic response of the polar clusters induced by the combined substitutions of Bi 3+ and Al 3+ on the Ba 2+ and Ti 4+ site. Moreover, the curie temperature of BBTA shows the decreasing trend compared to that of pure BaTiO 3 , which doesn't follow the normal Vegard's law, confirming that no BiAlO 3 sublattice formed in BBTA. All these features indicate that BBTA is a promising candidate for lead-free relaxors.

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Spin pumping occurred under nonlinear spin dynamic has been studied in Pt(17 nm)/Y3Fe5O12(YIG 66 nm) heterostructure. By using high power excitation, the precession angle (θc) of YIG can reach a value as high as 22°, and distinct nonlinear dynamic effects such as foldover ferromagnetic resonance spectra and nonlinear damping have been witnessed. The linear relation between the dc component of spin current and  sin2θc has been tested from linear to nonlinear spin dynamics regimes. Our main finding is that spin mixing conductance is a robust parameter that is independent on the amplitude and damping of the dynamic system, at least in our experiment conditions.

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