Showing papers on "Spin wave published in 2009"
TL;DR: Magnonic crystals are expected to provide full control of spin waves, similarly to what photonic crystals already do for light as mentioned in this paper, and combined with nonvolatility, multifunctional metamaterials might be formed.
Abstract: Magnetic nanostructures have long been in the focus of intense research in the magnetic storage industry. For data storage the nonvolatility of magnetic states is of utmost relevance. As information technology generates the need for higher and higher data-transfer rates, research efforts have moved to understand magnetization dynamics. Here, spin waves and their particle-like analog, magnons, are increasingly attracting interest. High-quality nanopatterned magnetic media now offer new ways to transmit and process information without moving electrical charges. This new functionality is enabled by spin waves. They are confined by novel functioning principles, which render them especially suitable to operate at the nanoscale. Magnonic crystals are expected to provide full control of spin waves, similarly to what photonic crystals already do for light. Combined with nonvolatility, multifunctional metamaterials might be formed. We report recent advances in this rapidly increasing research field called magnonics.
428 citations
TL;DR: In this paper, the authors give an overview of both theoretical and experimental developments concerning states with lattice symmetry breaking in the cuprate high-temperature superconductors. But the results obtained using the techniques of neutron and X-ray scattering and scanning tunnelling spectroscopy are not discussed.
Abstract: This article gives an overview of both theoretical and experimental developments concerning states with lattice symmetry breaking in the cuprate high-temperature superconductors. Recent experiments have provided evidence for states with broken rotation as well as translation symmetry, and will be discussed in terms of nematic and stripe physics. Of particular importance here are results obtained using the techniques of neutron and X-ray scattering and scanning tunnelling spectroscopy. Ideas on the origin of lattice-symmetry-broken states will be reviewed, and effective models accounting for various experimentally observed phenomena will be summarized. These include both weak-coupling and strong-coupling approaches, with a discussion of their distinctions and connections. The collected experimental data indicate that the tendency toward uni-directional stripe-like ordering is common to underdoped cuprates, but becomes weaker with increasing number of adjacent CuO2 layers.
366 citations
Book•
05 Apr 2009
TL;DR: In this paper, the propagation characteristics and excitation of dipolar spin wave are discussed. But the authors do not discuss the application of spin wave propagation in anisotropic-dispersive media.
Abstract: to Magnetism.- Quantum Theory of Spin Waves.- Magnetic Susceptibilities.- Electromagnetic Waves in Anisotropic-Dispersive Media.- Magnetostatic Modes.- Propagation Characteristics and Excitation of Dipolar Spin Waves.- Variational Formulation for Magnetostatic Modes.- Optical-Spin Wave Interactions.- Nonlinear Interactions.- Novel Applications.
309 citations
TL;DR: In this article, it was shown that antiferromagnetism has a role in the superconductivity of iron arsenide and that magnetism local, as described by the Heisenberg model, or itinerant, which is more in agreement with the Stoner model.
Abstract: It is likely that antiferromagnetism has a role in the superconductivity of iron arsenide. But is the magnetism local, as described by the Heisenberg model, or itinerant, which is more in agreement with the Stoner model? The answer is both.
276 citations
TL;DR: In this article, a register of quantum bits in different collective electron spin wave excitations in a solid medium is encoded by applying gradient magnetic fields across the sample, while a Cooper pair box, resonant with the cavity field, may be used to carry out one and two-qubit operations.
Abstract: We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium. Coupling to spins is enabled by locating them in the vicinity of a superconducting transmission line cavity, and making use of their strong collective coupling to the quantized radiation field. The transformation between different spin waves is achieved by applying gradient magnetic fields across the sample, while a Cooper pair box, resonant with the cavity field, may be used to carry out one- and two-qubit gate operations.
219 citations
TL;DR: In this article, a planar structure of magnonic-crystal waveguides, made of a single magnetic material, was reported, in which the allowed and forbidden bands of propagating dipole-exchange spin waves can be manipulated by the periodic modulation of different widths in thin-film nanostrips.
Abstract: We report, for the first time, on a novel planar structure of magnonic-crystal waveguides, made of a single magnetic material, in which the allowed and forbidden bands of propagating dipole-exchange spin waves can be manipulated by the periodic modulation of different widths in thin-film nanostrips. The origin of the presence of several magnonic wide band gaps and the crucial parameters for controlling those band gaps of the order of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{GHz}$ are found by micromagnetic numerical and analytical calculations. This work can offer a route to the potential application to broadband spin wave filters in the gigahertz frequency range.
212 citations
TL;DR: This work investigates the propagation of spin impurity atoms through a strongly interacting one-dimensional Bose gas, observing a very complex nonequilibrium dynamics, including the emergence of large density fluctuations in the remaining BoseGas, and multiple scattering events leading to dissipation of the impurity's motion.
Abstract: We investigate the propagation of spin impurity atoms through a strongly interacting one-dimensional Bose gas. The initially well localized impurities are accelerated by a constant force, very much analogous to electrons subject to a bias voltage, and propagate as a one-dimensional impurity spin wave packet. We follow the motion of the impurities in situ and characterize the interaction induced dynamics. We observe a very complex nonequilibrium dynamics, including the emergence of large density fluctuations in the remaining Bose gas, and multiple scattering events leading to dissipation of the impurity's motion.
201 citations
TL;DR: In this paper, the impact of the magnetic field angle on the oscillation frequency of a nanocontact spin torque oscillator (STO) in magnetic fields up to 2.1 T was studied.
Abstract: We study the impact of the magnetic field angle on the oscillation frequency of a nanocontact spin torque oscillator (STO) in magnetic fields up to 2.1 T. A model based on a single nonlinear, nonpr ...
187 citations
TL;DR: Inelastic neutron scattering measurements on single crystals of superconducting BaFe1.84Co0.16As2 reveal a magnetic excitation located at wave vectors in tetragonal notation, indicating that the magnetic fluctuations are two dimensional in nature.
Abstract: nelastic neutron scattering measurements on single crystals of superconducting BaFe1.84Co0.16As2 reveal a magnetic excitation located at wave vectors (1/2???1/2?? ?L) in tetragonal notation. On cooling below TC, a clear resonance peak is observed at this wave vector with an energy of 8.6(0.5) meV, corresponding to 4.5(0.3) kBTC. This is in good agreement with the canonical value of 5 kBTC observed in the cuprates. The spectrum shows strong dispersion in the tetragonal plane but very weak dispersion along the c axis, indicating that the magnetic fluctuations are two dimensional in nature. This is in sharp contrast to the anisotropic three dimensional spin excitations seen in the undoped parent compounds
162 citations
TL;DR: It is demonstrated that for a wave in a pure state of polarization, the spin-orbit interaction results in a spiraling power flow that is determined by the extent of the interaction, and the spin transport can be resonantly enhanced in a spherical geometry.
Abstract: Electromagnetic waves carry angular momenta, and, due to spin-orbit interaction, an encounter with a gradient of refractive index leads to transport of spin similar to the electronic spin Hall effect. We show here that transversal spin transport is possible even when the symmetry of optical interaction is of higher dimensionality. We demonstrate that for a wave in a pure state of polarization, the spin-orbit interaction results in a spiraling power flow that is determined by the extent of the interaction. As a result, the spin transport can be resonantly enhanced in a spherical geometry. Our results open the possibility for developing new functionalities for photonic devices.
155 citations
TL;DR: In this paper, the transmission of microwave spin waves through a microstructured magnonic crystal in the form of a Permalloy waveguide of a periodically varying width was studied experimentally and theoretically.
Abstract: Transmission of microwave spin waves through a microstructured magnonic crystal in the form of a Permalloy waveguide of a periodically varying width was studied experimentally and theoretically. The spin wave characteristics were measured by spatially resolved Brillouin light scattering microscopy. A rejection frequency band was clearly observed. The band gap frequency was controlled by the applied magnetic field. The measured spin-wave intensity as a function of frequency and propagation distance is in good agreement with a model calculation.
TL;DR: An extension of the Landau-Lifshitz-Gilbert (LLG) equation is proposed by explicitly including the role of conduction electrons in magnetization dynamics of conducting ferromagnets by containing highly spatial dependence of damping term and thus micromagnetic simulations based on the standard LLG equation should be reexamined.
Abstract: We propose an extension of the Landau-Lifshitz-Gilbert (LLG) equation by explicitly including the role of conduction electrons in magnetization dynamics of conducting ferromagnets. The temporal and spatial dependent magnetization order parameter m(r,t) generates both electrical and spin currents that provide dissipation of the energy and angular momentum of the processing magnet. The resulting LLG equation contains highly spatial dependence of damping term and thus micromagnetic simulations based on the standard LLG equation should be reexamined for magnetization dynamics involving narrow domain walls and spin waves with short wavelengths.
TL;DR: In this paper, a robust magnonic-crystal waveguide structure for use as an efficient gigahertz-range spin-wave filter that passes only spin waves of chosen narrow band frequencies and filters out the other frequencies was found.
Abstract: We found a robust magnonic-crystal waveguide structure for use as an efficient gigahertz-range spin-wave filter that passes only spin waves of chosen narrow band frequencies and filters out the other frequencies. The structure consists of the serial combinations of various width modulations with different periodicities and motifs in planar-patterned thin-film nanostrips composed of a single soft magnetic material. The observed magnonic band gaps result from both the translation symmetry of the one-dimensional width modulation and the higher-quantized width-mode spin waves excited from scattering at the periodic edge-steps of the width modulation. This work brings us one step closer to practical implementations of spin waves in information transmission and processing devices.
TL;DR: In this article, the transmission of microwave spin waves through a microstructured magnonic crystal in the form of a permalloy waveguide of a periodically varying width was studied experimentally and theoretically.
Abstract: Transmission of microwave spin waves through a microstructured magnonic crystal in the form of a permalloy waveguide of a periodically varying width was studied experimentally and theoretically. The spin wave characteristics were measured by spatially-resolved Brillouin light scattering microscopy. A rejection frequency band was clearly observed. The band gap frequency was controlled by the applied magnetic field. The measured spin-wave intensity as a function of frequency and propagation distance is in good agreement with a model calculation.
TL;DR: In this paper, the spin accumulation and spin precession in single layer graphene are studied by nonlocal spin valve measurements at room temperature, and the dependence of the nonlocal magnetoresistance on electrode spacing is investigated and the results indicate a spin diffusion length of ∼ 1.6μm and a spin injection/detection efficiency of 0.013.
Abstract: Spin accumulation and spin precession in single layer graphene are studied by nonlocal spin valve measurements at room temperature. The dependence of the nonlocal magnetoresistance on electrode spacing is investigated and the results indicate a spin diffusion length of ∼1.6 μm and a spin injection/detection efficiency of 0.013. Electrical detection of the spin precession confirms that the nonlocal signal originates from spin injection and transport. Fitting of the Hanle spin precession data yields a spin relaxation time of ∼84 ps and a spin diffusion length of ∼1.5 μm, which is consistent with the value obtained through the spacing dependence.
TL;DR: In this article, the spin accumulation and spin precession in single-layer graphene are studied by non-local spin valve measurements at room temperature and the dependence of the nonlocal magnetoresistance on electrode spacing is investigated and the results indicate a spin diffusion length of ~1.6 microns and a spin injection/detection efficiency of 0.013.
Abstract: Spin accumulation and spin precession in single-layer graphene are studied by non-local spin valve measurements at room temperature. The dependence of the non-local magnetoresistance on electrode spacing is investigated and the results indicate a spin diffusion length of ~1.6 microns and a spin injection/detection efficiency of 0.013. Electrical detection of the spin precession confirms that the non-local signal originates from spin injection and transport. Fitting of the Hanle spin precession data yields a spin relaxation time of ~84 ps and a spin diffusion length of ~1.5 microns, which is consistent with the value obtained through the spacing dependence.
TL;DR: Neutron scattering measurements of the magnetic excitations in single crystals of antiferromagnetic CaFe2As2 reveal steeply dispersive and well-defined spin waves up to an energy of approximately 100 meV, suggesting that the high energy behavior is dominated by the damping of spin waves by particle-hole excitations.
Abstract: Neutron scattering measurements of the magnetic excitations in single crystals of antiferromagnetic CaFe2As2 reveal steeply dispersive and well-defined spin waves up to an energy of approximately 100 meV. Magnetic excitations above 100 meV and up to the maximum energy of 200 meV are however broader in energy and momentum than the experimental resolution. While the low energy modes can be fit to a Heisenberg model, the total spectrum cannot be described as arising from excitations of a local moment system. Ab initio calculations of the dynamic magnetic susceptibility suggest that the high energy behavior is dominated by the damping of spin waves by particle-hole excitations.
TL;DR: The possibility that the chiral degeneracy of the magnons in ultrathin films can be lifted due to the presence of Dzyaloshinskii-Moriya interactions is raised and the asymmetry of the spin-wave spectrum is revealed in the case of wave vectors parallel to the (001) direction.
Abstract: We raise the possibility that the chiral degeneracy of the magnons in ultrathin films can be lifted due to the presence of Dzyaloshinskii-Moriya interactions. By using simple symmetry arguments, we discuss under which conditions such a chiral asymmetry occurs. We then perform relativistic first principles calculations for an Fe monolayer on W(110) and explicitly reveal the asymmetry of the spin-wave spectrum in the case of wave vectors parallel to the (001) direction. Furthermore, we quantitatively interpret our results in terms of a simplified spin model by using calculated Dzyaloshinskii-Moriya vectors. Our theoretical prediction should inspire experiments to explore the asymmetry of spin waves, with a particular emphasis on the possibility to measure the Dzyaloshinskii-Moriya interactions in ultrathin films.
TL;DR: High-resolution neutron diffraction and inelastic neutron scattering experiments in the frustrated multiferroic hexagonal compounds RMnO_{3} (R = Ho,Yb,Sc,Y), which provide evidence of a strong magnetoelastic coupling in the whole family.
Abstract: We have performed high-resolution neutron diffraction and inelastic neutron scattering experiments in the frustrated multiferroic hexagonal compounds RMn0 3 (R = Ho, Yb, Sc, Y), which provide evidence of a strong magnetoelastic coupling in the whole family. We can correlate the atomic positions, the type of magnetic structure, and the nature of the spin waves whatever the R ion and temperature. The key parameter is the position of the Mn ions in the unit cell with respect to a critical threshold of 1/3, which determines the sign of the coupling between Mn triangular planes.
TL;DR: In this article, the authors review neutron scattering investigations of the crystal structures, magnetic structures, and spin dynamics of the iron-based RFe(As, P)(O, F) (R = La, Ce. Pr, Nd), (Ba,Sr, Ca)Fe2As2, and Fe1+x(Te-Se) systems.
Abstract: We review neutron scattering investigations of the crystal structures, magnetic structures, and spin dynamics of the iron-based RFe(As, P)(O, F) (R = La, Ce. Pr, Nd), (Ba,Sr,Ca)Fe2As2, and Fe1+x(Te-Se) systems. On cooling from room temperature all the undoped materials exhibit universal behavior, where a tetragonal-to-orthorhombic/monoclinic structural transition Occurs, below which the systems become antiferromagnets. For the first two classes of materials the magnetic structure within the a-b plane consists of chains of parallel Fe spins that are coupled antiferromagnetically in the orthogonal direction, with an ordered moment typically less than one Bohr magneton. Hence these are itinerant electron magnets, with a spin structure that is consistent with Fermi-surface nesting and a very energetic spin wave bandwidth similar to 0.2 eV. With doping, the structural and magnetic transitions are suppressed in favor of superconductivity, with Superconducting transition temperatures up to approximate to 55 K. Magnetic correlations are observed in the Superconducting regime, With a Magnetic resonance that follows the Superconducting order parameter just like the cuprates. The rare earth moments order antiferromagnetically at low T like 'conventional' Magnetic Superconductors, while the Cc crystal field linewidths are affected when superconductivity sets in. The application of pressure in CaFe2As2 transforms the system from a magnetically ordered orthorhombic material to a 'collapsed' non-magnetic tetragonal system. Tetragonal Fe1+xTe transforms to a low T monoclinic structure at small x that changes to orthorhombic at larger x, which is accompanied by a crossover from commensurate to incommensurate magnetic order. Se doping Suppresses the magnetic order, while incommensurate magnetic correlations are observed in the superconducting regime. (C) 2009 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the frequency resolved magneto-optic Kerr effect was used to probe the spin dynamics and mode structure in 50-200-nm-diameter nanomagnets ranging from 3 to 10 nm in thickness.
Abstract: We use frequency resolved magneto-optic Kerr effect to probe the spin dynamics and mode structure in 50--200-nm-diameter ${\text{Ni}}_{80}{\text{Fe}}_{20}$ nanomagnets ranging from 3 to 10 nm in thickness. We find that the intrinsic Gilbert damping parameter is largely unaffected by the nanopatterning process despite a large linewidth dependence on the size of the nanomagnets. In the larger nanomagnets, both end and center modes are observed. The linewidth of these two modes differ considerably, which is most likely the result of the sensitivity of the end mode to small variations and imperfection of the shape and edge materials. We show that this effect can be exploited as a means to separately characterize the magnetic properties of the nanomagnets as well as the size and shape variations within the array.
TL;DR: In this paper, the authors present a theory for the dynamics of the magnon gas driven by a microwave field far out of equilibrium that provides rigorous support for the formation of quasiequilibrium Bose-Einstein condensation (BEC) of magnons in a YIG film magnetized in the plane.
Abstract: Strong experimental evidences of the formation of quasiequilibrium Bose-Einstein condensation (BEC) of magnons at room temperature in a film of yttrium iron garnet (YIG) excited by microwave radiation have been recently reported. Here we present a theory for the dynamics of the magnon gas driven by a microwave field far out of equilibrium that provides rigorous support for the formation of a BEC of magnons in a YIG film magnetized in the plane. We show that if the microwave driving power exceeds a threshold value the nonlinear magnetic interactions create cooperative mechanisms for the onset of a phase transition leading to the spontaneous generation of quantum coherence and magnetic dynamic order in a macroscopic scale. The theoretical results agree with the experimental data for the intensity and the decay rate of the Brillouin light scattering from the BEC as a function of power and for the microwave emission from the uniform mode generated by the confluence of BEC magnon pairs.
TL;DR: In this article, the operational characteristics of a magnonic crystal fabricated as an array of shallow grooves on a surface of a magnetic film were compared for magnetostatic surface spin waves and backward volume spin waves, and the rejection frequency bands formation was studied as a function of the grooves depth.
Abstract: The operational characteristics of a magnonic crystal, which was fabricated as an array of shallow grooves on a surface of a magnetic film, were compared for magnetostatic surface spin waves and backward volume magnetostatic spin waves. The rejection frequency bands formation was studied as a function of the grooves depth. It has been found that the rejection of the volume wave is considerably larger than of the surface one. The influences of the nonreciprocity of the surface spin waves, as well as of the scattering of the lowest volume spin-wave mode into higher ones on the rejection efficiency are discussed.
TL;DR: In this article, the operational characteristics of a magnonic crystal, which was fabricated as an array of shallow grooves etched on a surface of a magnetic film, were compared for magnetostatic surface spin waves and backward volume spin waves, and the formation of rejection frequency bands was studied as a function of the grooves depth.
Abstract: The operational characteristics of a magnonic crystal, which was fabricated as an array of shallow grooves etched on a surface of a magnetic film, were compared for magnetostatic surface spin waves and backward volume magnetostatic spin waves. In both cases the formation of rejection frequency bands was studied as a function of the grooves depth. It has been found that the rejection of the volume wave is considerably larger than of the surface one. The influences of the nonreciprocity of the surface spin waves as well as of the scattering of the lowest volume spin-wave mode into higher thickness volume modes on the rejection efficiency are discussed.
TL;DR: The current-induced modification of the attenuation of a propagating spin wave in a magnetic nanowire is studied theoretically and numerically to estimate the nonadiabaticity of the spin-transfer torque.
Abstract: The current-induced modification of the attenuation of a propagating spin wave in a magnetic nanowire is studied theoretically and numerically. The attenuation length of spin wave can increase when the spin waves and electrons move in the same direction. It is directly affected by the nonadiabaticity of the spin-transfer torque and thus can be used to estimate the nonadiabaticity. When the nonadiabatic spin torque is sufficiently large, the attenuation length becomes negative, resulting in the amplification of spin waves.
TL;DR: In this paper, a detailed first-principles study of Fe-pnictides with particular emphasis on competing magnetic interactions, structural phase transition, giant magneto-elastic coupling and its effect on phonons is presented.
Abstract: We present a detailed first-principles study of Fe-pnictides with particular emphasis on competing magnetic interactions, structural phase transition, giant magneto–elastic coupling and its effect on phonons. The exchange interactions J i , j ( R ) are calculated up to ≈12 A from two different approaches based on direct spin-flip and infinitesimal spin-rotation. We find that J i , j ( R ) has an oscillatory character with an envelop decaying as 1/ R 3 along the stripe-direction while it is very short range along the diagonal direction and antiferromagnetic. A brief discussion of the neutron scattering determination of these exchange constants from a single crystal sample with orthorhombic-twinning is given. The lattice parameter dependence of the exchange constants, dJ i , j / da are calculated for a simple spin-Peierls like model to explain the fine details of the tetragonal–orthorhombic phase transition. We then discuss giant magneto–elastic effects in these systems. We show that when the Fe-spin is turned off the optimized c -values are shorter than experimental values by 1.4 A for CaFe 2 As 2 , by 0.4 A for BaFe 2 As 2 , and by 0.13 A for LaOFeAs. We explain this strange behavior by unraveling surprisingly strong interactions between arsenic ions, the strength of which is controlled by the Fe-spin state through Fe–As hybridization. Reducing the Fe-magnetic moment, weakens the Fe–As bonding, and in turn, increases As–As interactions, causing a giant reduction in the c -axis. These findings also explain why the Fe-moment is so tightly coupled to the As-z position. Finally, we show that Fe-spin is also required to obtain the right phonon energies, in particular As c-polarized and Fe–Fe in-plane modes that have been recently observed by inelastic X-ray and neutron scattering but cannot be explained based on non-magnetic phonon calculations. Since treating iron as magnetic ion always gives much better results than non-magnetic ones and since there is no large c -axis reduction during the normal to superconducting phase transition, the iron magnetic moment should be present in Fe-pnictides at all times. We discuss the implications of our results on the mechanism of superconductivity in these fascinating Fe-pnictide systems.
TL;DR: Neutron scattering measurements show the ferromagnetic XY pyrochlore Yb2Ti2O7 to display strong quasi-two-dimensional spin correlations at low temperature, which give way to long range order (LRO) under the application of modest magnetic fields.
Abstract: Neutron scattering measurements show the ferromagnetic XY pyrochlore Yb2Ti2O7 to display strong quasi-two-dimensional (2D) spin correlations at low temperature, which give way to long range order (LRO) under the application of modest magnetic fields. Rods of scattering along 111 directions due to these 2D spin correlations imply a magnetic decomposition of the cubic pyrochlore system into decoupled kagome planes. A magnetic field of approximately 0.5 T applied along the [110] direction induces a transition to a 3D LRO state characterized by long-lived, dispersive spin waves. Our measurements map out a complex low temperature-field phase diagram for this exotic pyrochlore magnet.
TL;DR: In this paper, the inverse spin-Hall effect (ISHE) was used to measure spin wave resonance in Ni81Fe19/Pt thin wire arrays, and the experimental results indicated that the amplitude of the electromotive force is proportional to the spin-wave resonance absorption intensity.
Abstract: Spin wave resonance in Ni81Fe19/Pt thin wire arrays has been investigated using the inverse spin-Hall effect (ISHE). The spin wave in the Ni81Fe19 layer drives spin pumping, generation of spin currents from magnetization precession, and the pumped spin current is converted into a charge current by ISHE in the Pt layer. We found an electromotive force transverse to the spatial and the spin-polarization directions of the spin current. The experimental results indicate that the amplitude of the electromotive force is proportional to the spin wave resonance absorption intensity, enabling the electric measurement of spin wave resonance in nanostructured magnetic systems.
TL;DR: This work describes a technique that generalizes the traditional Kerr rotation approach to enable us to measure the electron spin coherence directly without needing to manipulate the spin dynamics, which allows for a spin projection measurement on an arbitrary set of basis states.
Abstract: Many proposed quantum information processing schemes rely on electron spin as the basic (quantum) unit of information. For this approach, careful preparation and read-out of the electron spin state, which can be done optically, are essential operations. Since coherence of the spin state is a manifestation of its quantum nature, both the preparation and read-out should be spin coherent. The traditional technique to measure spin coherence, based on the magneto-optical Kerr effect, measures spin population by the rotation of the reflected light polarization, but it requires an extra step of spin manipulation to project a measurement onto a fixed basis which is defined by the direction of the probe light beam. Kosaka et al. have developed a more straightforward and general scheme still based on Kerr rotation but modified so that a spin projection measurement can be done on an arbitrary set of basis states. This allows them to perform a direct tomographic measurement of electron spin precession in a semiconductor structure. The authors propose that the developed scheme offers a universal tool for performing preparation and read-out of a spin quantum state in a solid. A more straightforward and general scheme to measure electron spin coherence based on Kerr rotation but modified so that a spin projection measurement can be done on an arbitrary set of basis states has been developed. This allows a direct tomographic measurement of electron spin precession in a semiconductor structure, and offers a universal tool for performing preparation and read-out of a spin quantum state in a solid. Spin is a fundamental property of electrons, with an important role in information storage1,2,3,4. For spin-based quantum information technology, preparation and read-out of the electron spin state are essential functions5,6,7,8,9,10,11,12,13. Coherence of the spin state is a manifestation of its quantum nature, so both the preparation and read-out should be spin-coherent. However, the traditional spin measurement technique based on Kerr rotation, which measures spin population using the rotation of the reflected light polarization that is due to the magneto-optical Kerr effect, requires an extra step of spin manipulation or precession to infer the spin coherence14,15,16,17,18,19,20. Here we describe a technique that generalizes the traditional Kerr rotation approach to enable us to measure the electron spin coherence directly without needing to manipulate the spin dynamics, which allows for a spin projection measurement on an arbitrary set of basis states. Because this technique enables spin state tomography, we call it tomographic Kerr rotation. We demonstrate that the polarization coherence of light is transferred to the spin coherence of electrons, and confirm this by applying the tomographic Kerr rotation method to semiconductor quantum wells with precessing and non-precessing electrons. Spin state transfer and tomography offers a tool for performing basis-independent preparation and read-out of a spin quantum state in a solid.
TL;DR: In this paper, the propagation of spin waves in microscopic transversally magnetized permalloy stripe waveguides with variable width was studied experimentally and it was shown that due to the variation in the internal demagnetizing fields caused by the width variation, an effective control of the spin-wave propagation can be achieved.
Abstract: We have studied experimentally the propagation of spin waves in microscopic transversally magnetized permalloy stripe waveguides with variable width. Spatially resolved measurement based on the microfocus Brillouin light-scattering spectroscopy allowed a direct observation of transformations of propagating transverse spin-wave modes in the region of the width transition. Our experiments show that due to the variation in the internal demagnetizing fields caused by the width variation, an effective control of the spin-wave propagation can be achieved. In particular, a splitting of a spin-wave beam into two independent beams or preferred excitation of certain transverse spin-wave modes can be realized.