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We discuss the correspondence between the current-induced spin polarization in non-centrosymmetric magnetic metals and the linear magnetoelectric effect in non-centrosymmetric magnetic insulators using a linear-response theory and the concept of magnetoelectric multipoles. We show that the magnetoelectric toroidal moment is a particularly useful quantity since it determines the ground-state antiferromagnetic domain of a non-centrosymmetric antiferromagnet in the presence of a steady-state electric current. We analyze two prototypical antiferromagnetic spintronic materials- Mn 2 Au and CuMnAs-and show that the experimentally reported domain reorientations are consistent with the alignment of their toroidal moments parallel to the applied electric current. Finally, we determine whether similar behavior should be expected in the prototypical insulating magnetoelectric materials, Cr 2 O 3 and Li M PO 4, if they could be doped into a semiconducting or metallic regime. ISSN:0021-8979 ISSN:1089-7550

The spread of the Cooper pairs into the ferromagnet in proximity coupled superconductor - ferromagnet (SF) structures is shown to cause a strong inverse electromagnetic phenomenon, namely, the long-range transfer of the magnetic field from the ferromagnet to the superconductor. Contrary to the previously investigated inverse proximity effect resulting from the spin polarization of superconducting surface layer, the characteristic length of the above inverse electrodynamic effect is of the order of the London penetration depth, which usually much larger than the superconducting coherence length. The corresponding spontaneous currents appear even in the absence of the stray field of the ferromagnet and are generated by the vector-potential of magnetization near the S/F interface and they should be taken into account at the design of the nanoscale S/F devices. Similarly to the well-known Aharonov-Bohm effect, the discussed phenomenon can be viewed as a manifestation of the role of vector potential in quantum physics., Comment: 5 pages, 4 figures

We have studied the coherent spin dynamics of excitons bound to acceptors, A0X, immersed in a CdTe quantum well by using time resolved photo-induced Faraday rotation. We have also measured the time-resolved differential transmission in order to determine a A0X lifetime of 220 ps, which is independent of the applied magnetic field. We show that at low magnetic field, the spin of A0X is completely frozen during a time, ≅ 4.5 ns, at least twenty times longer than its lifetime. We compare the spin properties of A0X with the spin properties of other charged excitons systems, and we conclude that the hyperfine interaction of the photo-created electron spin with nuclear spins is very likely to be at the origin of the observed spin dephasing times. Fil: Grinberg, Patricio. Universite Paris Sorbonne - Paris Iv; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Bernardot, F.. Universite Paris Diderot - Paris 7; Francia. Universite Paris Sorbonne - Paris Iv; Francia Fil: Eble, B.. Universite Paris Sorbonne - Paris Iv; Francia Fil: Karczewski, G.. Institute Of Physics Of The Polish Academy Of Sciences; Polonia Fil: Testelin, C.. Universite Paris Sorbonne - Paris Iv; Francia Fil: Chamarro, M.. Universite Paris Sorbonne - Paris Iv; Francia

We present a theory of spin dynamics caused by spin-orbit coupling for two-dimensional gases of cold atoms and other quasiparticles with pseudospin 1/2 moving in orbital gauge fields. Our approach is based on the gauge transformation in the form of a SU(2) rotation gauging out the spin-orbit coupling. As a result, the analysis of the spin dynamics is reduced to calculation of the density-related susceptibility of the system without spin-orbit coupling at the wavevector determined by the spin-rotation length. This approach allows one to treat the spin dynamics in terms of the linear response theory for bosonic and fermionic ensembles. We study different regimes of irreversible spin relaxation and coherent spin dynamics in these systems. For bosonic gases the effects of low temperature are crucial due to accumulation of particles in the small-momentum subspace even if the Bose–Einstein condensation does not occur due to the system low dimensionality., We acknowledges funding by the Spanish MEC (FIS2010-21282-C02-01 and FIS2012-36673-C03-01) and “Grupos Consolidados UPV/EHU del Gobierno Vasco” (IT-319-07 and IT-472-10). The contribution of EYS was, in addition, supported by the University of Basque Country UPV/EHU under program UFI 11/55.

Under the terms of the Creative Commons Attribution 3.0 Unported License to their work., We show here that using spin orbit coupling interactions at a metallic interface it is possible to control the sign of the spin to charge conversion in a spin pumping experiment. Using the intrinsic symmetry of the “Inverse Rashba Edelstein Effect” (IREE) in a Bi/Ag interface, the charge current changes sign when reversing the order of the Ag and Bi stacking. This confirms the IREE nature of the conversion of spin into charge in these interfaces and opens the way to tailoring the spin sensing voltage by an appropriate trilayer sequence., We would like to acknowledge financial support from the European Commission through the Marie Curie Intra European Fellowship Project No. 301656: AtomicFMR, funded by the 7th Framework Programme. This work was supported by Spanish Ministry of Economy and Competitivity through Project No. MAT2011-27553-C02, including FEDER funds, and by the Aragon Regional Government.

The control of individual magnetic domain walls has potential for future spintronic memory and data processing applications. The speed and reliability of such devices are determined by the dynamic properties of the domain walls. Typically, spin precession limitations lead to Walker breakdown, limiting wall velocity resulting in low mobility. Here, we show the suppression of Walker breakdown by the careful design of small amplitude periodic nanowire structuring to match the periodicity of domain wall spin structure transformations. This opens up a channel for energy dissipation via spin wave emission, allowing a domain wall to maintain its spin structure during propagation.

We propose a quantum interference spin-injector nanodevice consisting of a superconductor-normal metal hybrid loop connected to a superconductor- ferromagnet bilayer via a tunneling junction. We show that for certain values of the applied voltage bias across the tunnel barrier and the magnetic flux through the loop, the spin-current can be fully polarized. Moreover, by tuning the magnetic flux, one can switch the sign of the spin polarization. This operation can be performed at frequencies within the tens of GHz range. We explore the nanodevice in a wide range of parameters, establish the optimum conditions for its experimental realization, and discuss its possible applications. © 2013 AIP Publishing LLC., F.G. acknowledges the FP7 program No. 228464 MICROKELVIN, the Italian Ministry of Defense through the PNRM project TERASUPER, and the Marie Curie Initial Training Action (ITN) Q-NET 264034 for partial financial support. The work of F.S.B. was supported by the Spanish Ministry of Economy and Competitiveness under Project FIS2011-28851-C02-02.

The polarization of the direct gap emission from Ge/SiGe multiple quantum wells has been studied in the 4 K to 300 K temperature range, and in samples with different well thicknesses. Our results demonstrate that the polarization type and degree strongly depend on the excitation of electrons from the heavy hole and the light hole subbands, thus providing an effective degree of freedom to control the polarization of the direct interband emission. In addition, the analysis of the temperature dependence of the polarization degree highlights spin depolarization mechanisms.

Point contact Andreev reflection measurements show a correlation between measured spin polarization and the interface scattering parameter Z extracted from fits of the modified Blonder–Tinkham–Klapwijk model to the conductance–voltage curves of superconductor/ferromagnet point contacts. We present a simple spin–flip scattering model which identifies Z2 as the effective scattering parameter and explains the observed exponential decay of the spin polarization.

We studied the transport of photoinjected spins in GaAs by time-resolved photoluminescence measurements. At low temperatures, the spin polarization after drift transport of 4 μm is found to decrease as the applied electric field E increases to a few kV/cm, and it disappears when E exceeds 3 kV/cm. The origin of the field-dependent spin relaxation is discussed.

We measure the statistical polarization of quadrupolar nuclear spins in a sub-micrometer (0.6 um^3) particle of GaAs using magnetic resonance force microscopy. The crystalline sample is cut out of a GaAs wafer and attached to a micro-mechanical cantilever force sensor using a focused ion beam technique. Nuclear magnetic resonance is demonstrated on ensembles containing less than 5 x 10^8 nuclear spins and occupying a volume of around (300 nm)^3 in GaAs with reduced volumes possible in future experiments. We discuss how the further reduction of this detection volume will bring the spin ensemble into a regime where random spin fluctuations, rather than Boltzmann polarization, dominate its dynamics. The detection of statistical polarization in GaAs therefore represents an important first step toward 3D magnetic resonance imaging of III-V materials on the nanometer-scale., 20 pages, 6 figures, 1 supplementary file

High-mobility two-dimensional electron systems may be one of the bases of future spintronic devices, where the spin states of ballistic electrons could be manipulated via external gate voltages and the resulting spin-orbit fields. Therefore, the knowledge of spin dynamics in such systems is of technical interest and offers on the other side an exciting view on the underlying physics. Here, we present time-resolved Faraday rotation measurements in a high-mobility two-dimensional electron system in a GaAs/AlGaAs quantum well structure grown along the [001] direction. Even without applied external magnetic fields the optically generated spin ensemble shows a coherent precession about the effective spin-orbit field. If a nonquantizing magnetic field is applied normal to the sample plane, the effective spin-orbit fields are rotated by the cyclotron motion of the electrons. This rotation leads to fast oscillations in the spin polarization about a nonzero value and an strong increase of the spin dephasing times. The measurement data is in excellent agreement with a model based on a kinetic equation approach., AIP Conf. Proc. 1399

With the recent discovery of very long hole spin decoherence times in GaAs/AlGaAs heterostructures of more than 70 ns in two-dimensional hole systems, using the hole spin as a viable alternative to electron spins in spintronic applications seems possible. Furthermore, as the hyperfine interaction with the nuclear spins is likely to be the limiting factor for electron spin lifetimes in zero dimensions, holes with their suppressed Fermi contact hyperfine interaction due to their p-like nature should be able to show even longer lifetimes than electrons. For spintronic applications, electric-field control of hole spin dynamics is desirable. Here, we report on time-resolved Kerr rotation and resonant spin amplification measurements on a two-dimensional hole system in a p-doped GaAs/AlGaAs heterostructure. Via a semitransparent gate, we tune the charge density within the sample. We are able to observe a change in the hole g factor, as well as in the hole spin dephasing time at high magnetic fields., AIP Conf. Proc. 1399

Spins in semiconductor structures may allow for the realization of scalable quantum bit arrays, an essential component for quantum computation schemes. Specifically, hole spins may be more suited for this purpose than electron spins, due to their strongly reduced interaction with lattice nuclei, which limits spin coherence for electrons in quantum dots. Here, we present resonant spin amplification (RSA) measurements, performed on a p-modulation doped GaAs-based quantum well at temperatures below 500 mK. The RSA traces have a peculiar, butterfly-like shape, which stems from the initialization of a resident hole spin polarization by optical orientation. The combined dynamics of the optically oriented electron and hole spins are well-described by a rate equation model, and by comparison of experiment and model, hole spin dephasing times of more than 70 ns are extracted from the measured data., AIP Conf. Proc. 1399

Spin‐dependent observables have been a powerful tool to probe the internal structure of the nucleon and to understand the dynamics of the strong interaction. Experiments involving spin degrees of freedom have lead to numerous surprises, puzzles and discoveries. The so called “spin crisis” in the 1980s revealed the limitation of naive quark‐parton models and led to intensive worldwide efforts, both experimental and theoretical, to understand the nucleon spin structure. The nucleon spin structrue study has grown from mainly on the longitudinal spin in the last thirty years to recently rapidly increasing interests on the transverse spin. With high intensity and high polarization of both the electron beam and targets, JLab has the world's highest polarized luminosity and the best figure‐of‐merit for precision spin structure measurements. It has made a strong impact in this subfield of research. This proceeding will highlight JLab Hall A's study in the measurements of the moments of spin structure functions at...

Experiments in spintronics necessarily involve the detection of spin polarization. The sensitivity of this detection becomes an important factor to consider when extending the low temperature studies on semiconductor spintronic devices to room temperature, where the spin signal is weaker. In pump-probe experiments, which optically inject and detect spins, the sensitivity is often improved by using a photoelastic modulator (PEM) for lock-in detection. However, spurious signals can arise if diode lasers are used as optical sources in such experiments, along with a PEM. In this work, we eliminated the spurious electromagnetic coupling of the PEM onto the probe diode laser, by the double modulation technique. We also developed a test for spurious modulated interference in the pump-probe signal, due to the PEM. Besides, an order of magnitude enhancement in the sensitivity of detection of spin polarization by Kerr rotation, to 3x10(-8) rad was obtained by using the concept of Allan variance to optimally average the time series data over a period of 416 s. With these improvements, we are able to experimentally demonstrate at room temperature, photoinduced steady-state spin polarization in bulk GaAs. Thus, the advances reported here facilitate the use of diode lasers with a PEM for sensitive pump-probe experiments. They also constitute a step toward detection of spin-injection in Si at room temperature.

Date of Conference: 22-26 August 2006 Conference Name: 6th International Conference of the Balkan Physical Union, 2006 We study the magnetic behavior and in particular the spin susceptibility of an interacting two-dimensional electron gas in a finite in-plane magnetic field. The total energy of the system is constructed using the recent quantum Monte Carlo simulation based parametrized correlation energy as a function of density, spin polarization, and applied magnetic field. The critical magnetic field to fully spin polarize the system is obtained as a function of the electron density. The spin polarization as a function of the applied field (less than the critical field) for various densities are calculated. The spin susceptibility as a function of the applied field for various densities are calculated. The zero-field value of the spin susceptibility as a function of electron density is compared with relevant experiments.

An update is given of the ongoing experimental investigation of the spin structure of the nucleon, with particular emphasis on the COMPASS results, and some mentioning of the ongoing spin experiments at RHIC. Both longitudinal and transverse spin phenomena are covered. In the first case, the hot topic is the direct measurement of the gluon polarisation. Evidence is presented for ΔG/G being small around xg≃0.1, and its first moment should not be larger than 0.2–0.3 in absolute value. About transverse spin effects, evidence is given for new phenomena, associated with transverse momentum dependent distribution and fragmentation functions, which might explain the transverse spin phenomena observed since long time in pp scattering.

application/pdf, We have measured photoluminescence (PL) spectra and time-resolved PL in CdTe quantum dots (QDs) under the longitudinal magnetic field up to 10T. Circular polarization of PL increases with increasing magnetic field, while its linear polarization is absent under linearly polarized excitation. Time-resolved PL measurements clarified that this behavior is caused by the suppression of spin relaxation induced by the longitudinal magnetic field. We believe that this behavior is related to the hyperfine interaction of electron spin with magnetic momenta of lattice nuclei.

The authors demonstrate polarization transfer from a photon to an electron spin intermediated by a light-hole exciton in a GaAs∕AlGaAs quantum well, which has an engineered electron g factor of less than 0.01 for an in-plane magnetic field. Negative spin polarization was clearly observed at the selective excitation of the light-hole exciton from two-color time-resolved Kerr rotation. This demonstration is a necessary step towards demonstrating coherence transfer from a photon to an electron spin, which is necessary for building a quantum repeater used for long distance quantum communications.

The understanding of charged particle orbital dynamics in an electromagnetic field is necessary for the acceleration and the storage of particles. The understanding of spin (or magnetic moment) dynamics is essential for the acceleration and the storage of polarized particle beams. In this paper we review the analysis of the dynamics of the spin and the various schemes and devices up‐to‐date to manipulate the spin to conserve the polarization while accelerating and storing a polarized beam. We shall concentrate on hadrons such as protons, antiprotons and heavier ions although most of the discussions apply equally well to leptons. Electron and positron beams are self‐polarizing through spin‐flip synchrotron radiation at high energies and hence the acceleration of polarized e± beams is less relevant. (AIP)

This paper reviews the theoretical description of the surface region of Heisenberg magnets, both at low temperatures in the spin wave regime, and near the ordering temperature. The results of new studies of instabilities in the spin configuration at the surface are presented, and the experimental data on magnetic properties of the surface are reviewed briefly.