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Random spin fluctuations in an equilibrium ensemble of paramagnetic spins are shown to contain valuable information about the system itself. We use off-resonant Faraday rotation to passively and sensitively "listen" to the random magnetization fluctuations (spin noise) in atomic alkali vapors. These random fluctuations generate spontaneous spin coherences which precess and decay with the same characteristic energy and time scales as the macroscopic magnetization of an intentionally polarized or driven ensemble. Correlation spectra of the measured spin noise reveals g-factors, nuclear spin, isotope abundance ratios, hyperfine splittings, nuclear moments, and spin coherence lifetimes -- without having to excite, optically pump, or otherwise drive the spin system away from thermal equilibrium. These noise signatures scale inversely with interaction volume, suggesting routes towards non-perturbative, sourceless magnetic resonance of small solid state spin systems.

A spin-polarized dc current can induce steady-state, microwave frequency magnetization dynamics in a nanoscale ferromagnet. The torque that drives these dynamics originates from the exchange of spin angular momentum between conduction electrons and the magnetization. We present measurements of current perpendicular to the plane (CPP) giant magnetoresistance (GMR) nanopillar devices in which this phenomenon occurs. We focus on devices that contain one reference ferromagnetic layer that has a fixed magnetization and one free ferromagnetic layer with a magnetization that responds to spin torque. The resulting spin transfer induced magnetization dynamics combined with GMR lead to resistance noise, which we measure in both the frequency- and time-domain. The appearance of these dynamical states is consistent with spin transfer in that dynamics are observed only for those combinations of current direction and magnetic configuration in which spin torque opposes the FL configuration set by the magnetic field. Furthermore, the amplitude of the resultant resistance noise increases rapidly with increasing current until saturating at a value that is a large fraction of the magnetoresistance between parallel and antiparallel states. This behaviour is contrasted with similar measurements of a current-in-plane (CIP) GMR device in which the magnetic resistance noise is thermally activated.

We studied the influence of the populations of neutral and positively charged excitons (trions) on optical absorption of modulation p-doped CdTe-based quantum wells. The density of 2D hole gas in the quantum well was controlled by an additional cw illumination in the range from 10 10 cm -2 to 10 11 cm -2 . Time-resolved absorption was measured following a picosecond, circularly polarized, resonant pump pulse, which created significant exciton population. A spectrally broad femtosecond probe pulse was used to detect the absorption over the excitonic region, including exciton, trion and biexciton transition energies. Besides, we used a small magnetic field (below 1T) to create a steady-state spin polarization of the hole gas. By exploiting polarization-dependent selection rules, we were able to identify exciton, trion and biexciton absorption lines without ambiguity. We studied the evolution of these absorption lines under influence of photo-created populations of excitons and trions. The results are interpreted in terms of spin-dependent exciton-exciton and exciton-carrier interaction, the latter being dominant, in contrast with results obtained on GaAs-based quantum wells. We propose a new explanation of the oscillator strength stealing phenomena observed in doped quantum wells, based on the screening of neutral excitons by charge carriers. We have also found that binding holes into charged excitons excludes them from the interaction with the rest of the system, so that oscillator strength stealing is partially blocked. Experimental evidence is presented for creation of a transient spin polarization in the system by a circularly polarized pump pulse.

We present a scheme to control the spin-polarization of photoelectrons/photoions using short laser pulses. It is based on the pump-probe method. By exciting fine structure manifolds of a system by the short pump pulse with a sufficient bandwidth, a superposition of fine structure states is created. After the pump pulse, the coherently superposed excited state evolves in time under the field-free condition with a period determined by the inverse of energy difference between them. In terms of the spin state, this suggests that the different spin state evolves differently in time, leading to the time-varying spin-polarization. Therefore, varying the time delay between the pump and probe pulses leads to the control of spin states upon photoionization. Specific theoretical results are presented for two-valence-electron atoms, in particular for Mg, which demonstrate that, under certain conditions, not only the degree of spin-polarization but also its polarity can be manipulated through time delay. Furthermore, we propose a new technique to accelerate the coupling time by the introduction of a dressing laser with a few ns duration. Since the underline physics is rather general and transparent, the presented scheme may be potentially applied to nanostructures such as quantum wells and quantum dots.

In this work, we investigate the effect of anti-site disorder on the half-metallic properties of a Mn2FeAl Heusler alloy thin film. The film was grown on TiN-buffered MgO 001 substrates via magnetron sputtering. A detailed structural characterization using x-ray diffraction (XRD) and anomalous XRD showed that the film crystallizes in the partially disordered L21 B structure with 33% disorder between the Mn(B) and Al(D) sites. We measure a positive anisotropic magnetoresistance in the film, which is an indication of non-half metallic behaviour. Our x-ray magnetic circular dichroism sum rules analysis shows that Mn carries the magnetic moment in the film, with a positive Fe moment. Experimentally determined moments correspond most closely with those found by density functional calculated for the L21 B structure with Mn(B) and Al(D) site disorder, matching the experimental structural analysis. We thus attribute the deviation from half-metallic behaviour to the formation of the L21 B structure. To realize a half-metallic Mn2FeAl film it is important that the inverse Heusler XA structure is stabilized with minimal anti-site atomic disorder.

Spin-reorientation magnetic transitions are studied in Mn-doped SmFeO3., Spin reorientation is a magnetic phase transition in which rotation of the magnetization vector with respect to the crystallographic axes occurs upon a change in the temperature or magnetic field. For example, SmFeO3 shows a magnetization rotation from the c axis above 480 K to the a axis below 450 K, known as the Γ4 → Γ2 transition. This work reports the successful synthesis of the new single-crystal perovskite SmFe0.75Mn0.25O3 and finds interesting spin reorientations above and below room temperature. In addition to the spin reorientation of the Γ4 → Γ2 magnetic phase transition observed at around T SR2 = 382 K, a new spin reorientation, Γ2 → Γ1, was seen at around T SR1 = 212 K due to Mn doping, which could not be observed in the parent rare earth perovskite compound. This unexpected spin configuration has complete antiferromagnetic order without any canting-induced weak ferromagnetic moment, resulting in zero magnetization in the low-temperature regime. M–T and M–H measurements have been made to study the temperature and magnetic-field dependence of the observed spin reorientation transitions.

Atomic and electronic structure of graphene/Ni(111), h-BN/Ni(111) and graphene/h-BN/Ni(111) nanocomposites with different numbers of graphene and h-BN layers and in different mutual arrangements of graphene/Ni and h-BN/Ni at the interfaces was studied using LDA/PBC/PW technique. Using the same technique corresponding graphene, h-BN and graphene/h-BN structures without the Ni plate were calculated for the sake of comparison. It was suggested that C-top:C-fcc and N-top:B-fcc configurations are energetically favorable for the graphene/Ni and h-BN/Ni interfaces, respectively. The Ni plate was found to induce a significant degree of spin polarization in graphene and h-BN through exchange interactions of the electronic states located on different fragments.

On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

I.V. Bryakin1, bivas2006@yandex.ru, I.V. Bochkarev2, elmech@mail.ru, V.R. Khramshin3, hvrmgn@gmail.com. 1 Institute of Automation and Information Technologies, National Academy of Sciences of the Kyrgyz Republic, Bishkek, Kyrgyz Republic, 2 Kyrgyz State Technical University named after I. Razzakov, Bishkek, Kyrgyz Republic, 3 Nosov Magnitogorsk State Technical University, Magnitogorsk, Russian Federation. Брякин Иван Васильевич, д-р техн. наук, профессор, директор, Институт автоматики и информационных технологий НАН КР, г. Бишкек, Кыргызская Республика; bivas2006@yandex.ru. Бочкарев Игорь Викторович, д-р техн. наук, профессор, профессор кафедры «Электромеханика», Кыргызский государственный технический университет им. И. Раззакова, г. Бишкек, Кыргызская Республика; elmech@mail.ru. Храмшин Вадим Рифхатович, д-р техн. наук, профессор, профессор кафедры «Электроснабжение промышленных предприятий», Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; hvrmgn@gmail.com. This paper proposes a novel nondestructive testing method for electrically conductive objects. It is based on applying a fundamentally new physical effect which has not been used before in nondestructive testing systems. The method utilizes spin polarization phenomena that occur when free electrons of conductive materials are exposed to an alternating electric field. Researchers experimented with wire and cable conductors. A tested cable was moving longitudinally and exposed to an alternating electric field, which excited a waveform process, i.e. the polarization of spin magnetic moments of free electrons. An induction sensor registered this process and generated a control signal: induction EMF. Its parameters were compared against that of a reference signal obtained in advance in the same way utilizing spin polarization phenomena. Parametric deviations were then used to detect and classify conductor defects. The paper describes how to generate a reference signal appropriate for the objectives of testing. The developed method enables nondestructive testing of objects made of any conductive para- and diamagnetic materials, while it accuracy and reliability are not affected by the magnitude or evenness of the object movement speed, nor by vibrations or transverse oscillations against the physical field source or the induction sensor. Предложен новый метод неразрушающего контроля электропроводящих объектов. Он основан на применении принципиально нового, не используемого ранее в системах неразрушающего контроля фи- зического эффекта. Для реализации этого метода используются спин-поляризационные явления, возни- кающие при воздействии переменного электрического поля на свободные электроны электропроводя- щих материалов. В качестве объекта контроля в статье рассмотрены электропроводящие элементы элек- трических проводов и кабелей. На продольно перемещающийся контролируемый кабель воздействуют направленным переменным электрическим полем, которым в электропроводящих элементах кабеля воз- буждают волновой физический процесс в виде поляризации спиновых магнитных моментов свободных электронов. Индукционным датчиком регистрируют этот процесс и формируют контрольный сигнал в виде ЭДС индукции. Параметры контрольного сигнала сравнивают с параметрами опорного сигнала, полученного заранее аналогичным образом с применением спин-поляризационных явлений. Наличие и вид дефекта электропроводящих элементов определяют по полученным отклонениям указанных пара- метров. Описан процесс формирования опорного сигнала в зависимости от поставленных целей контро- ля. Разработанный метод обеспечивает возможность проведения неразрушающего контроля объектов из любых электропроводящих пара- и диамагнитных материалов, причем точность и надежность контроля не зависит от величины и равномерности скорости перемещения объекта контроля, а также от вибрации и его поперечных колебаний относительно источника физического поля и индукционного датчика.

This paper is dealing with the rutile structure of TiO2 and the effect due to the vacancy of oxygen at a particular site by the first-principle calculation. The geometric places of oxygen site and the attribution of single and double sites were investigated in this study. The TiO2 with selected site vacancies of oxygen can be treated as TiO2−δ (the form of defects in rutile). The DFT calculations have been done for the spin polarization. The Boltzmann transportation theory was applied to investigate the transport properties for temperature from 80 to 1000 K. Great variations have been observed in parameters (thermal and electric conductivities, Seebeck coefficient and Hall coefficient) in terms of the functions of temperature. The paper described how the particular site vacancy of oxygen plays a significant role.

Cofunctionality---the coexistence of different (possibly even contraindicated) properties in the same compound---is an exciting prospect that never fails to deliver interesting surprises, as in transparent while electrically conducting compounds, topological insulators having Rashba spin split bands, or electrically conducting while thermally insulating (thermoelectric) compounds. Here we study a cofunctionality of ferroelectricity and Rashba effect that combines the directional helical spin-polarization characteristic of the energy bands of bulk Rashba compounds with the existence of two opposite electric polarization states, characteristic of atomic displacements in displacive ferroelectrics. Flipping of the ferroelectric polarization (e.g., via an applied electric field) would result in the reversal of the Rashba spin polarization. However, thus far, only very few (essentially one) compounds have been found to be ferroelectric Rashba semiconductors (FERSCs), e.g., GeTe ($R3m$). In this paper, we propose a general strategy for the identification of compounds that possess cofunctionalities and apply it to perform an inverse design, finding compounds that simultaneously have ferroelectricity and Rashba spin splitting. The inverse design combining functionality ${f}_{1}$ with ${f}_{2}$ involves definition and utilization of causal factors that enable the said functionalities, and involves three steps: (1) screening materials that satisfy the enabling DPs common to the two functionalities ${f}_{1}$ and ${f}_{2}$; (2) filtering the materials according to DPs that are unique to each of the individual functionalities ${f}_{1}$ and ${f}_{2}$; and (3) by using the ensuing two compound lists of compounds $C({f}_{1})$ and $C({f}_{2})$ identifying the intersection between them, i.e., compounds $C({f}_{1},{f}_{2})$ possessing simultaneous ${f}_{1}$ and ${f}_{2}$. Based on this process, we design 52 atomic combinations not suspected to be FERSCs that were previously synthesized. Of these 52 compounds, we find 24 FERSCs that are thermodynamically stable (i.e., reside on the convex hull) and, at the same time, feature larger spin splitting (large than 25 meV). These include ${\mathrm{BrF}}_{5}(Cmc{2}_{1})$, $\mathrm{TlI}{\mathrm{O}}_{3}(R3m)$, $\mathrm{Zn}{\mathrm{I}}_{2}{\mathrm{O}}_{6}(P{2}_{1})$, $\mathrm{LaTa}{\mathrm{O}}_{4}(Cmc{2}_{1})$, ${\mathrm{Tl}}_{3}{\mathrm{S}}_{3}\mathrm{Sb}(R3m)$, ${\mathrm{Sn}}_{2}{\mathrm{P}}_{2}{\mathrm{Se}}_{6}$ (Pc), and ${\mathrm{Bi}}_{2}\mathrm{Si}{\mathrm{O}}_{5}(Cmc{2}_{1})$ that have Rashba spin splitting of 31, 57, 111, 40, 90, 67, and 76 meV, respectively. Density functional theory calculations illustrate the reversal of the spin texture when the electric polarization is flipped. This paper validates a general approach for the search of other cofunctionalities based on causal enabling design principles rather than uncovering machine correlations.

A paper has recently been published which describes the technique of so-called ‘spin tune mapping’ to measure the ‘stable spin axis’ (spin closed orbit) of a spin polarized beam circulating in a storage ring. This paper presents an independent analysis of the technique, and significantly different findings are reported below. In particular, it is derived that there are several unquantified systematic errors which are not treated in the previous analysis.

Spin waves are a promising prospect for the development of microwave information processing devices. A major obstacle in the study of spin waves is the large intrinsic spin-wave damping in most known magnetic materials. Viable spin-wave amplification techniques are thus required to make further progress in the development of spin-wave-based logic devices. In this paper, we investigate a novel technique of parametric modulation of spin waves using bulk acoustic waves. Although it is not a conclusive proof of parametric amplification, we show that bulk acoustic waves at twice the frequency of the propagating spin waves on coupling into an yttrium iron garnet film can modulate the amplitude of the spin wave. This paper provides insight into magnon-phonon interactions, and suggests a new mechanism to compensate for inherent losses in spin-wave propagation in spin-wave-based logic devices.

The paper critically overviews the recent developments of the theory of spatially dispersive spin fluctuations (SF) in itinerant electron magnetism with particular emphasis on spin-fluctuation coupling or spin anharmonicity. It is argued that the conventional self-consistent renormalized (SCR) theory of spin fluctuations is usually used aside of the range of its applicability actually defined by the constraint of weak spin anharmonicity based on the random phase approximation (RPA) arguments. An essential step in understanding SF in itinerant magnets beyond RPA-like arguments was made recently within the soft-mode theory of SF accounting for strong spin anharmonicity caused by zero-point SF. In the present paper we generalize it to apply for a wider range of temperatures and regimes of SF and show it to lead to qualitatively new results caused by zero-point effects.

This paper describes the physics of collective excitations that are caused by spin-transfer torques in CFAS magnetic multilayer. When the magnetizations of the pinned and free layers are not collinear with each other, the spin-polarized currents transfer angular momentum to the magnetizations near the interfaces, giving rise to spin-transfer torques. The currents in magnetic multilayer are spin polarised and can carry enough angular momentum. When an electron spin carried by the current interacts with a magnetic layer, the exchange interaction leads to torque between the spin and the magnetization vector of the free layer. This is Spin Transfer Torque (STT) and it excites the magnetization when it is large enough. The Spin Transfer Torque induced collective excitations for the CFAS spin valve pillar have been extensively studied in this paper.

In this paper, we elucidate the changes of magnetoelectric coupling mechanism in different zones of the rich magnetic field-temperature $(B\text{\ensuremath{-}}T)$ phase diagram of the molecular multiferroic ${(\mathrm{N}{\mathrm{H}}_{4})}_{2}[\mathrm{FeC}{\mathrm{l}}_{5}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{H}}_{2}\mathrm{O}]$, which represents one of the rare cases where improper ferroelectricity has been observed in a hybrid material. We have recently proposed a mechanism of multiferroicity in zero magnetic field in the deuterated form of this material from a detailed determination of its crystal and magnetic structures. The proposed magnetic structure at zero magnetic field corresponds to a cycloidal spin arrangement that gives rise to a ferroelectric polarization through the spin current mechanism induced via the inverse Dzyaloshinskii-Moriya interaction. In this paper, we present a single-crystal neutron diffraction study under external magnetic field, aimed at elucidating the evolution of the magnetic structure under applied magnetic field, and determine the mechanism of magnetoelectric coupling, which allows us to describe an unprecedented change from spin current to spin-dependent $p\text{\ensuremath{-}}d$ hybridization mechanism.

In a recent paper, Gohler et al. [1] report that a high efficiency electron spin filter can be constructed from an adsorbed monolayer of double-stranded DNA (dsDNA). Understanding the mechanisms responsible for spin filtering under these conditions has proven to be a challenge, as classical analysis fails to account for the high degree of polarization observed. In this paper we show that these observations can be understood since conduction electrons in the DNA molecule are characterized by specific helical states having a magnetic moment opposite to the direction of the electron wavevector. These helical states are fundamental to the quantum-mechanical properties of periodic structures with helical symmetry. Free electrons passing through the DNA monolayer interact with these helical states, but the strength of this interaction depends on the relative orientation of the electron spin and the magnetic moment associated with the possible helical states. One of these configurations leads to a negligible interaction resulting in high spin polarization in the transmitted electron beam. The overall effect is that the free electron flux component with a magnetic moment in an opposite direction to the magnetic moment of the helical states can pass through the dsDNA monolayer without absorption, while the other spin component is highly absorbed by dsDNA. This is consistent with the finding that a monolayer of single-stranded DNA does not exhibit similar spin filtering properties.

The paper reviews the interplay of Rashba/Dresselhaus spin splittings in various two-dimensional systems made of zinc-blende III–V, wurtzite, and SiGe semiconductors. We discuss the symmetry aspects of the linear and cubic in electron wavevector spin splitting in heterostructures prepared on (001)-, (110)-, (111)-, (113)-, (112)-, and (013)- oriented substrates and address the requirements for suppression of spin relaxation and realization of the persistent spin helix state. In experimental part of the paper, we overview experimental results on the interplay of Rashba/Dresselhaus spin splittings probed by photogalvanic spectroscopy: The method based on the phenomenological equivalence of the linear-in-wavevector spin splitting and several photogalvanic phenomena.

Half-metallic Co-based full Heusler alloys have been qualified as promising functional materials in spintronic devices due to their high spin polarization. The lack of perpendicular magnetic anisotropy (PMA) is one of the biggest obstacles restricting their application in next generation ultrahigh density storage such as magnetic random access memory (MARM). How to induce the PMA in Co-based full Heusler alloy thin films has attracted much research interest of scientists. This paper presents an overview of recent progress in this research area. We hope that this paper would provide some guidance and ideas to develop highly spin-polarized Co-based Heusler alloy thin films with PMA.

This paper investigates the structure of a spin electromagnetic (EM) field and its various physical properties. A spin EM field is an intrinsic mode of free space, which satisfies the spin equations derived from Maxwell equations. A spin mode has two basic properties: the spin along its axis and the localization of electromagnetic field. The source and EM structure of this electric and magnetic mode are described in detail in this paper. The distributed charge and current of a spin mode can be integrated to obtain the electric and magnetic moment, and they can be treated as the electromagnetic dipole. A spin mode possesses both wave and particle properties: a wave number, angular frequency and characteristic speed are its wave parameters; an intrinsic radius, energy and angular momentum are its dynamic parameters. The former is analogous to an EM resonant mode; the latter is similar to the behavior of a particle with intrinsic spin. There are two kinds of electric modes present, one can be expressed through a pair of charges, and the other can be expressed by a magnetic current. They both have the same electric moment, but have different divergence properties.

The mesoscopic transport physics of spin Hall effect and quantized spin Hall effect is briefly reviewed. This paper concentrates on the universal spin Hall conductance fluctuations discovered in both effects. We present various model Hamiltonians corresponding to different physical problems arising recently in condensed matter physics, ranging from two-dimensional electron gas to topological insulators. Green's function formalism within a tight-binding model and the random matrix theory are introduced to study the same electron transport mechanism. The calculated spin Hall conductance results are discussed and some excellent agreement has been found from different approaches. A short summary and our perspectives are provided at the end of paper.

Spin angular momentum transfer, or spin-transfer, describes the transfer of spin angular momentum between a spin-polarized current and a ferromagnetic conductor. The angular momentum transfer exerts a torque (spin-current induced torque, or spin-torque) on the ferromagnetic conductor. When its dimensions are reduced to less than 100 nm, the spin-torque can become comparable to the magnetic damping torque at a spin-polarized current of high current density (above 106 A/cm2), giving rise to a new set of current-induced dynamic excitation and magnetic switching phenomena. This has now been definitively observed in sub-100-nm current-perpendicular spin-valves and magnetic tunnel junctions, and appears promising as a basis for direct write-address of a nanomagnetic bit when the lateral bit size is reduced to well below 100 nm. An overview is presented in this paper of spin-transfer phenomena. The first part of the paper contains a brief introduction to spin-transfer, especially the characteristic dynamics associated with spin-torque. In the second part, several representative experiments are described. In the third part, a set of basic phenomenological models are introduced that describe experimental observations. The models also serve as a bridge for quantitative comparison between experiments and first-principles spin-polarized transport theory. In the last part of the paper, some device concepts based on spin-transfer-induced magnetic excitation and magnetic reversal are described.

Spin-based electronics promises a radical alternative to charge-based electronics, namely the possibility of logic operations with much lower power consumption than equivalent charge-based logic operations. In this paper we review three potential means of dissipationless spin transport in semiconductors with and without spin-orbit coupling: the use of spin currents, propagating modes, and orbital currents. Spin and orbital currents induced by electric fields obey a fundamentally different law than charge transport, which is dissipative. Dissipationless spin currents occur in materials with strong spin-orbit coupling, such as GaAs, while orbital currents occur in materials with weak spin-orbit coupling, such as Si, but with degenerate bands characterized by an atomic orbital index. Spin currents have recently been observed experimentally. Propagating modes are the coupled spin-charge movement that occurs in semiconductors with spin-orbit coupling. In contrast to normal charge transport, which is diffusive, the spin-charge mode can exhibit propagating transport, with low energy loss over relatively large distances (>100 µm), by funneling energy between the spin and the charge component through the spin-orbit coupling channel. This opens the possibility for spin-based transport without either spin injection or spin detection. The schemes discussed in this paper are analyzed in comparison with schemes based on molecular electronics phenomena, dilute magnetic semiconductors, etc.

Half-Heusler alloys are prominent material for spintronics devices as these materials usually exhibit high spin polarization. But this spin polarization is severely affected by various disorders and distortions which ultimately hinders their practical applications. This paper examines the effect of the uniaxial strain as well as the tetragonal strain on the electronic and magnetic properties of half-Heusler FeCrAs alloy. This work is carried out by using the first-principles density functional theory calculations using the Wein2k software. The results of our study show that FeCrAs alloy exhibiting AFM and FM characteristics in u- strain while showing only FM characteristics in t- strain. The Half metallicity of the FeCrAs is sensitive in negative u-strain while it is quite robust in positive u-strain and t-strain the FeCrAs. The maximum value of band gap at 0% tetragonal-strain is about 1.04 eV. The FeCrAs Heusler alloy preserve the 100% spin polarization for whole studied range of tetragonal-strain (−10% to 10%). This property may make this system a promising candidate for spin transfer torque application.

The paper discusses the magnetization dynamics of spin-torque oscillator with negative K u under alternative head field for microwave assisted magnetic recording. Magnetization switching of spin-injection layer (SIL) is essential to have the same precession mode of the field generation layer before and after the head field change directions. The SIL needs to be properly chosen in order to have short switching time. The layer stack and material selection of spin torque oscillator (STO) is also discussed in terms of stability against the stray field. The results discussed in this paper helps to understand the design fundamentals of STO for microwave assisted magnetic recording.

In a recent paper we have demonstrated how a simple modification to the standard rotational echo double resonance pulse sequence, where the flip angle of the pulse applied to the S spin is varied, can be used to separate the measurement of the magnitude of I–S dipole–dipole couplings from that of their relative orientation. An equivalent result can be achieved via phase modulation which labels and differentiates between different evolving coherences in the density matrix based on the number of S spins participating—exactly as is done in multiple quantum spectroscopy. As phase modulation can be effected on modern instruments with much higher precision, in this paper we explore the experimental implementation of this method in the IS2 spin system glycine–13C2–15N, and discuss generalizations of this technique to larger spin systems.

The spin-polarized self-consistent-charge extended Huckel tight-binding (SP-SCC-XHTB) method has been developed by authors to study the electronic structures of rutile-type transition metal dioxides, MO2, with both the nonmagnetic and magnetic phases. This method has been used to successfully predict the electronic structures of nonmagnetic (n) MO2’s with M =Ti, V, Nb, Ta, Cr and ferromagnetic (f) CrO2, but is inadequate to predict the value of the energy gap of a semiconductive n-MnO2. The SP-SCC-XHTB band structure calculation, which includes all the relativistic effects in a first principal manner, has only one empirical parameter on the evaluation of the matrix elements of the non-relativistic Hamiltonian H0. In this paper, the SP-SCC-XHTB method is improved so as to evaluate the matrix elements of the H0 in a more appropriate manner. The band structure calculations are carried out for the n-MO2’s with M =Ti, V, Nb, Ta, Cr and Mn, the f-CrO2 and the af-MnO2. With the improvement it is shown that the SP-SCC-IXHTB band structure calculations give reasonable results for the electronic structures of all the MO2’s considered in the present paper.

In this paper, we investigate the structural, the electronic and the magnetic properties of the equiatomic quaternary Heusler alloy CoRuMnGe using the first-principle calculations. In fact, we appl...

In this paper, we present the results obtained from our study on the heat current across double quantum dots in serial coupled to ferromagnetic leads (FM-DQDs-FM), when the leads magnetic moments are in antiparallel configuration. This study was done by using nonequilibrium Green's function method in the linear response regime. Our results are calculated in weak interdot coupling regime by taking all the parameters that affect the system such as intradot Coulomb correlation energy, spin–spin exchange interaction, and spin polarization on the leads. These results are accomplished as a function of temperature gradient as well as quantum dots energy levels. According to our results, it is noticed that the values of intradot Coulomb correlation energy and the spin–spin exchange interaction have significant impact on increasing the heat current that flows through our system. It is concluded that increasing or decreasing the magnitude of heat current in negative or positive thermal bias is ideal for designing high-efficiency heat diode.

In this paper we develop a theoretical framework for studying spin polarization of one or both of the two electrons emitted in the one-photon, one-step, double ionization of an atom. The expressions derived herein are in the form of an incoherent sum over the angular momentum ${j}_{t}$ exchanged between the unobserved initial and final angular momenta. It then naturally facilitates an analysis of spin-resolved double-photoionization processes in terms of the parity-favored and -unfavored transitions. Several photon-propagation and electron-detection configurations are considered in which it becomes simpler to study the angular-spin or spin-spin correlation between two photoelectrons. The approach suggested in this paper has been used to analyze spin-resolved double photoionization in the ${6s}^{2}$ subshell of atomic ytterbium.

Background . This work is devoted to the application of geometrical optics formalism to describe the behavior of spin waves, which is propagating in a ferromagnetic medium with non-uniform distribution of magnetic parameters. Use of this approach allows to describe the process of refraction of spin waves to determine the focal length of spin lenses or mirrors and to operate it by changing the frequency of the spin wave with a given magnetic parameters of a medium. Objective. The objective is to calculate the index of refraction, reflection coefficient and focal length of spin lens as function of frequency of spin waves, the external magnetic field and magnetic parameters of the medium. Methods. In this paper, to find the refractive index and the focal length was used the geometrical optics approach. To describe the dynamics of the magnetization vector the formalism was used of the parameter of order of spin density that also gives an opportunity to use the methods of quantum mechanics to calculate the spin wave reflection coefficient. Results. In the paper the refractive index and focal length of a bulk spin lens have been found. By considering the generalized boundary conditions the expression has been found for the reflection coefficient of spin lens. In addition, results of investigation says that strong dependence exists of transparency of spin lens on the frequency of spin waves that is characterized by corresponding magnetic parameters of structure. Conclusions. It is shown the possibility to change “optical” spin lens parameters in a wide range of values by changing only the frequency of spin waves and keeping constant the values of the external magnetic field and magnetic structure parameters. In addition, the results of studies prove that exists a strong dependence of the spin lens transparency on the quality of its borders, which is characterized by appropriate parameters of interface.

In previous papers we generalized the ether waves associated to photons, to waves generally denoted , associated to Par(m,e)s, (particles of mass m and electric charge e), and demonstrated that a Par(m,e)s is a superposition of such waves that forms a small globule moving with the velocity of this . That, at a point near to a moving , the ether velocity , i.e., the magnetic field H, is of the same form as that of a point of a rotating solid. This is the spin of the Par(m,e)s, in particular, of the electron. Then, we considered the case where e=0 and showed that the perturbation caused by the motion of a Par(m,e)s is also propagated in the ether, and is a propagating gravitational field such that the Newton approximation (NA) is a tensor Guobtained by applying the Lorenz transformation for Vm,o on the NA of the static gravitational potential of forces Gu,s. It appeared that Gu is also of the form of a Lienard-Wiechert potential tensor Au created by an electric charge.In the present paper, we generalized the above results regarding the spin by showing that the ether elasticity theory implies also that like the electron, the massive neutral particle possesses a spin but much smaller than that of the electron, and that the photon can possess also a spin, when for example it is circularly polarized. In fact, we show that the spin associated to a particle is a vortex in ether which in closed trajectories will take only quantized values.

Half-metallic Co-based full Heusler alloys have been qualified as promising functional materials in spintronic devices due to their high spin polarization. The lack of perpendicular magnetic anisotropy (PMA) is one of the biggest obstacles restricting their application in next generation ultrahigh density storage such as magnetic random access memory (MARM). How to induce the PMA in Co-based full Heusler alloy thin films has attracted much research interest of scientists. This paper presents an overview of recent progress in this research area. We hope that this paper would provide some guidance and ideas to develop highly spin-polarized Co-based Heusler alloy thin films with PMA.

In this paper the dominant effect of electron inertia on the dynamics of localized density excitations is studied in a quantum plasma in the presence of electron spin effects. Using the quantum magnetohydrodynamics (QMHD) model including electron tunneling and spin polarization phenomena, it is revealed that the quantum effects such as plasma paramagnetism and diamagnetism play inevitable role on soliton existence criteria in quantum plasmas. Furthermore, it is shown that the magnetosonic localized density-excitation stability depends strongly on the quantum system dimensionality. Two distinct region of soliton stability is shown to exist depending on the value of the electron effective mass, where, the soliton amplitude variation with respect to the external magnetic field strength is quite opposite in these regions. Current findings can be important in the study of dynamical nonlinear wave features in dense laboratory or inertial-confined plasmas., Comment: Paper accepted in journal IEEE Trans. Plasma Sci

This paper develops theoretical expressions to study angular distribution and spin polarization of those Auger electrons which are emitted in the decay of a vacancy created by the absorption of a photon in a rotating linear molecule. Identical expressions except, of course, for different decay amplitudes, in both the Hund’s coupling schemes (a) and (b), are obtained for the differential Auger current emitted in the transition J→Jf measured by an electron spectrometer sensitive to spin detection. The structure of these angular distributions is exactly the same as that of the spin‐resolved photoelectrons from unoriented atoms and molecules. The present paper thus puts the angle‐ and spin‐resolved Auger and photoelectron spectroscopies on the same footing wherein identical geometrical and kinematical analysis is applicable. The four parameters needed to completely characterize such distributions depend, in the present case, on rotational orientation and/or alignment of the photoexcited molecule, in addition ...

In this paper, an ab initio study of the electronic and magnetic properties of CdS doped by the transition metal elements has been investigated. Based on the KKR-CPA method within the Generalized Gradient Approximation (GGA), we have calculated the total energy to determine the most stable state in the system and found it to be the ferromagnetic state for Ti, V and Cr-doped CdS, while it is the stabilization in spin glass states for Mn and Co cases. On the other hand, we have investigated and plotted the density of states (DOSs) which reveals that the doped compounds exhibit a half-metallic character. The spin polarization at Fermi level is estimated and found to be around 100%. Furthermore, we have identified the type of mechanism of exchange interactions being double exchange for all components except Mn case where we find that the responsible mechanism is the p-d exchange. The evaluation of the Curie temperature variation TC for the three components stable in the ferromagnetic phase revealed values greater than 300 K for most cases. The effect of the crystal field and the exchange splitting as a function of the concentrations values has been also investigated. Half-metallic substances are very interesting for spin-dependent electronics devices as they boost their magnetoresistance capacity.

Magnetic sensing based on nitrogen-vacancy (NV) centers in diamond have been considered by scientists to be a promising candidate for highly sensitive, integrated solid-state quantum sensors. In this paper, a displacement detection system is presented relying on the quantum magnetic effect of NV ensemble under a microwave (MW), which consists of a fluorescence microscope system and a bundle of movable current-carrying coils. The fluorescence microscope system is responsible for efficient fluorescence excitation and collection to identify the energy level splitting of electron spin. Moreover, the current-carrying coils are responsible for creating a gradient magnetic field with high linearity. Measurement by experiment, the theory sensitivity limit of the proposed device can up to 2.713 nm/Hz1/2, and the noise sensitivity is $51.93~\mu \text{m}$ /Hz1/2 when the coils carry the current 0.1 A. The response of fluorescence intensity (PL) to displacement can be up to 0.493%/mm for $\vert + 1\rangle $ sublevel with a measurement range of 12.57 mm and 0.419%/mm for $\vert - 1\rangle $ sublevel with a measurement range of 13 mm. Through experimental verification, the sensitivity and response can increase proportionally with the current, while the measurement range is inversely reduced. In view of this, the proposed displacement detection system can be used in displacement detection applications of different precision.

This paper presents a theoretical study of angular distribution of spin-resolved electrons ejected by interaction of light in the nonrelativistic, electric dipole approximation with nonlinear molecules oriented in space. A theory, formulated in an earlier paper [N. Chandra, Phys. Rev. A 40, 752 (1989)] by taking full account of the group-theoretical transformation properties of a molecular target, is used to develop explicit expressions for the four parameters [namely, the spin-unresolved differential cross section ${\mathit{d}}^{2}$\ensuremath{\sigma}(${\mathit{m}}_{\mathit{r}}$)/dk^d\ensuremath{\omega} for photoionization and the three polarization parameters \ensuremath{\chi}(${\mathit{m}}_{\mathit{r}}$,k,\ensuremath{\omega}), \ensuremath{\kappa}(${\mathit{m}}_{\mathit{r}}$,k,\ensuremath{\omega}), and \ensuremath{\zeta}(${\mathit{m}}_{\mathit{r}}$,k,\ensuremath{\omega}) that depend upon the state of polarization ${\mathit{m}}_{\mathit{r}}$ for the ionizing radiation, propagation vector k, and the orientation of the molecule in space] needed to describe the angularly distributed, spin-polarized photocurrent from linear as well as nonlinear molecules of any symmetry corresponding to one of the 32 point groups, oriented in space in their gaseous phase or on liquid (solid) surfaces.These formulas have been applied to angle- and spin-resolved photoelectron spectroscopy of the ${\mathit{a}}_{1}$ orbital in those molecules that transform like the ${\mathit{T}}_{\mathit{d}}$ point symmetry group. The spin polarization of photoelectrons in this case is due directly to the spin-orbit interaction in the molecular continua. Detailed expressions for the four parameters with the electric vector in the radiation beam both parallel and perpendicular to the fixed axis of the oriented molecule are derived, probably in their simplest possible form, using the concepts of the extended (or spin-double) group. The properties of these parameters, which are influenced, inter alia, also by the spin-orbit interaction, are analyzed. Such angle- and spin-resolved studies of photoionization in oriented molecules will therefore provide more stringent tests for theoretical models, probes into the effects of target orientation on photoionization dynamics, and a measure of the influence of the spin-orbit interaction on the continuum part of the spectrum.The procedure adopted and the formulation presented herein set a methodology and a framework for the analysis of the measurements and calculations of angle- and spin-resolved photoelectron spectra of those polyatomics in general, and ${\mathit{T}}_{\mathit{d}}$ molecules, in particular, which have a fixed orientation in space. The specific examples considered in this paper are photoionization in 4${\mathit{a}}_{1}^{2}$, 6${\mathit{a}}_{1}^{2}$, and 7${\mathit{a}}_{1}^{2}$ orbitals of oriented ${\mathrm{CF}}_{4}$, ${\mathrm{CCl}}_{4}$, and ${\mathrm{SiCl}}_{4}$, respectively. Without performing any dynamical calculations, the variations of various parameters with respect to the energy of the incident radiation and to the phases involved have semiempirically been studied in detail for two different orientations of the axis of the fixed molecule. This study has helped also in predicting the values of the polarization parameters in the energy range of the Cooper minimum for angle- and spin-resolved ${\mathrm{CCl}}_{4}$(6${\mathit{a}}_{1}^{2}$${)}^{\mathrm{\ensuremath{-}}1}$ and ${\mathrm{SiCl}}_{4}$(7${\mathit{a}}_{1}^{2}$${)}^{\mathrm{\ensuremath{-}}1}$ photoelectron spectra in oriented molecular targets.

Magnetoresistive Random Access Memory (MRAM) is a promising device for high-density (over Gbits scale), high-speed (equal to DRAM or better) non-volatile RAM, and much research has been done over several years with a view to overcoming the problems regarding practical use. Spin Torque Transfer switching MRAM (STT-MRAM) is considered to be the most promising candidate and there already are some papers on this new device. MgO is expected to be the best material for magnetic tunnel junction (MTJ) of STT-MRAM, because MgO-MTJ is known to show large Magnetoresistance (MR) and enhance spin polarization by the coherent tunneling effect, resulting in decrease of writing current of MTJ. MgO-MTJ has been shown to be an excellent barrier with little resistance drift compared with MTJ using alumina. Notwithstanding its excellent potential, the degradation mechanism of MgO-MTJ has not been well understood. In this paper, we will demonstrate for the first time the degradation of coherent tunneling and trapping phenomena of MgO-MTJ and discuss its mechanism.

This thesis work aims at a better understanding of magneto-optical properties of dilute nitrides and II-VI diluted magnetic semiconductor quantum structures. The thesis is divided into two parts. The first part gives an introduction of the research fields, together with a brief summary of the scientific results included in the thesis. The second part consists of seven scientific articles that present the main findings of the thesis work. Below is a short summary of the thesis. Dilute nitrides have been of great scientific interest since their development in the early 1990s, because of their unusual fundamental physical properties as well as their potential for device applications. Incorporation of a small amount of N in conventional Ga(In)As or Ga(In)P semiconductors leads to dramatic modifications in both electronic and optical properties of the materials. This makes the dilute nitrides ideally suited for novel optoelectronic devices such as light emitting devices for fiber-optic communications, highly efficient visible light emitting devices, multi-junction solar cells, etc. In addition, diluted nitrides open a window for combining Si-based electronics with III-V compounds-based optoelectronics on Si wafers, promising for novel optoelectronic integrated circuits. Full exploration and optimization of this new material system in device applications requires a detailed understanding of their physical properties. Papers I and II report detailed studies of effects of post-growth rapid thermal annealing (RTA) and growth conditions (i.e. presence of N ions, N2 flow, growth temperature and In alloying) on the formation of grown-in defects in Ga(In)NP. High N2 flow and bombardment of impinging N ions on grown sample surface is found to facilitate formation of defects, such as Ga interstitial (Gai) related defects, revealed by optically detected magnetic resonance (ODMR). These defects act as competing carrier recombination centers, which efficiently decrease photoluminescence (PL) intensity. Incorporation of a small amount of In (e.g. 5.1%) in GaNP seems to play a minor role in the formation of the defects. In GaInNP with 45% of In, on the other hand, the defects were found to be abundant. Effect of RTA on the defects is found to depend on initial configurations of Gai related defects formed during the growth. In Paper III, the first identification of an interfacial defect at a heterojunction between two semiconductors (i.e. GaP/GaNP) is presented. The interface nature of the defect is clearly manifested by the observation of ODMR lines originating from only two out of four equivalent orientations. Based on its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I=1/2), the defect is concluded to involve a P atom at its core with a defect/impurity partner along a direction. Defect formation is shown to be facilitated by N ion bombardment. In Paper IV, the effects of post-growth hydrogenation on the efficiency of the nonradiative (NR) recombination centers in GaNP are studied. Based on the ODMR results, incorporation of H is found to increase the efficiency of the NR recombination via defects such as Ga interstitials. In Paper V, we report on our results from a systematic study of layered structures containing an InGaNAs/GaAs quantum well, by the optically detected cyclotron resonance (ODCR) technique. By monitoring PL emissions from various layers, the predominant ODCR peak is shown to be related to electrons in GaAs/AlAs superlattices. This demonstrates the role of the SL as an escape route for the carriers confined within the InGaNAs/GaAs single quantum well. The last two papers are within a relatively new field of spintronics which utilizes not only the charge (as in conventional electronics) but also the quantum mechanical property of spin of the electron. Spintronics offers a pathway towards integration of information storage, processing and communications into a single technology. Spintronics also promises advantages over conventional charge-based electronics since spin can be manipulated on a much shorter time scale and at lower cost of energy. Success of semiconductor-based spintronics relies on our ability to inject spin polarized electrons or holes into semiconductors, spin transport with minimum loss and reliable spin detection. In Papers VI and VII, we study the efficiency and mechanism for carrier/exciton and spin injection from a diluted magnetic semiconductor (DMS) ZnMnSe quantum well into nonmagnetic CdSe quantum dots (QD’s) by means of spin-polarized magneto PL combined with tunable laser spectroscopy. By means of a detailed rate equation analysis presented in Paper VI, the injected spin polarization is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin injection process. In Paper VII, we present evidence that energy transfer is the dominant mechanism for carrier/exciton injection from the DMS to the QD’s. This is based on the fact that carrier/exciton injection efficiency is independent of the width of the ZnSe tunneling barrier inserted between the DMS and QD’s. In sharp contrast, spin injection efficiency is found to be largely suppressed in the structures with wide barriers, pointing towards increasing spin loss.

In this paper, we study and discuss the ab initio method and Monte Carlo simulations of the Fe2MnSn full Heusler alloy for the both structures: XA and L21. In fact, we have computed the structural, the electronic, the magnetic and the critical magnetic behavior of this alloy. Firstly, we have performed the ab initio calculations using the GGA approximations. The results of the electronic structures show that the full Heusler Fe2MnSn alloy shows a half-metallic character and a 100% spin polarization, only for the XA phase, at the Fermi level. This half-metallic behavior is confirmed by the integral value of the computed total magnetic moment value (6.00 μB). For non-null temperature values, we illustrate the magnetization behavior by using the Monte Carlo simulations (MCS) under the Metropolis algorithm. The magnetizations are illustrated and discussed as a function of the temperature and the exchange coupling interactions. To complete this study, we present and discuss the Monte Carlo results and compared them with the existing experimental values in the literature.

This paper theoretically examines the spin-dependent transport of electrons through InAs/GaAs symmetric triple barriers by solving the spin-dependent Schrodinger equation. The Transfer Matrix Method (TMM) was used to investigate the impact of the hydrostatic pressure, temperature, and magnetic field on the transmission coefficient and spin polarization of electrons while taking into account the Rashba and Dresselhaus spin orbit interactions. The results indicate that when both the hydrostatic pressure and temperature increase, the two resonant states of spin-up and down electrons move toward lower energies (blue shift). In addition, when the magnitude of the applied magnetic field increases, the resonant states of spin-up electrons shift toward lower energies, whereas the spin-down ones shift toward higher energies, which leads to perfect spin separation. This important spin-separation behavior could be very useful in the design of spin filters, which are strongly required in spintronics applications.

Electrides, with interstitial electrons loosely trapped in lattice voids behaving as anions, are favorable for achieving band inversions required for topological phases. In this paper, we predict that the quantum anomalous Hall effect (QAHE) with either in-plane or out-of-plane magnetization can be realized in gadolinium monohalides GdX (X = F, Cl, Br, and I), a new class of two-dimensional electrides. The spin polarization of interstitial electrons contributes to the ferromagnetism and stabilizes the crystal structure. Our calculations demonstrate that monolayer GdX are intrinsic QAHE insulators with in-plane magnetization and have band gaps up to 48.6 meV. Furthermore, we show that an external magnetic field can be used to realize the QAHE with out-of-plane magnetization, such as in monolayer GdI with the largest band gap of 84.3 meV among all halides considered in this work. The estimated Curie temperatures of GdX are about 510–650 K, which is above room temperature. Our studies reveal that the GdX electrides provide an attractive platform for exploring tunable, large-gap QAHE and open up opportunities to design new high-temperature quantum devices.

A mechanism is proposed for manipulating the magnetic state of a helical spin density wave using a current. In this paper, we show that a current through a bulk system with a helical spin density wave induces a spin transfer torque, giving rise to a rotation of the order parameter.The use of spin transfer torque to manipulate the magnetization in bulk systems does not suffer from the obstacles seen for magnetization reversal using interface spin transfer torque in multilayered systems. We demonstrate the effect by a quantitative calculation of the current induced magnetization dynamics of Erbium. Finally we propose a setup for experimental verification., Comment: In the previous version of this paper was a small numerical mistake made when evaluating equation 3 and 9. The number of digits given in the calculation of the torque current tensor is reduced to better represent the accuracy of the calculation. A slightly modified paper have been published in Phys. Rev. Lett. 96, 256601 (2006) 4 pages 3 figures

In this paper, two ferromagnetic insulating oxides, BiMnO/sub 3/(BMO) and NiFe/sub 2/O/sub 4/(NFO) were discussed. NFO presented the advantage that its electronic and magnetic properties can be tuned by controlling growth conditions. BMO epitaxial thin films were prepared by pulsed laser deposition while NFO spinel films were grown by rf sputtering. Magnetization, tunneling magnetoresistance and spin polarization were measured for both materials.

To a particle physicist a muon is a member of the lepton family, a heavy electron possessing a mass of about 1/9 that of a proton and a spin of 1/2, which interacts with surrounding atoms and molecules electromagnetically. Since its discovery in 1937, the muon has been put to many uses, from tests of special relativity to deep inelastic scattering, from studies of nuclei to tests of weak interactions and quantum electrodynamics, and most recently, as a radiographic tool to see inside heavy objects and volcanoes. In 1957 Richard Garwin and collaborators, while conducting experiments at the Columbia University cyclotron to search for parity violation, discovered that spin-polarized muons injected into materials might be useful to probe internal magnetic fields. This eventually gave birth to the modern field of μSR, which stands for muon spin rotation, relaxation or resonance, and is the subject of this special issue of Journal of Physics: Condensed Matter. Muons are produced in accelerators when high energy protons (generally >500 MeV) strike a target like graphite, producing pions which subsequently decay into muons. Most experiments carried out today use relatively low-energy (~4 MeV), positively-charged muons coming from pions decaying at rest in the skin of the production target. These muons have 100% spin polarization, a range in typical materials of about 180 mg cm-2, and are ideal for experiments in condensed matter physics and chemistry. Negatively-charged muons are also occasionally used to study such things as muonic atoms and muon-catalysed fusion. The μSR technique provides a local probe of internal magnetic fields and is highly complementary to inelastic neutron scattering and nuclear magnetic resonance, for example. There are four primary μSR facilities in the world today: ISIS (Didcot, UK), KEK (Tsukuba, Japan), PSI (Villigen, Switzerland) and TRIUMF (Vancouver, Canada), serving about 500 researchers world-wide. A new facility, JPARC (Tokai, Japan), is currently being built to replace the current Japanese μSR capability at KEK. These μSR institutions provide scientists a variety of sample environments, including a range of temperatures, magnetic fields and applied pressure. In addition, very low-energy muon beams (< 1 keV) have been developed for studies of thin films and nano-materials. In 2002 this world-wide community founded the International Society of μSR Spectroscopy (http://musr.org/~isms/) in order to promote the health of this growing field of research. The 20 papers presented in this volume are intended to highlight some of the current μSR research activities of interest to condensed matter physicists. It is not an exhaustive review. In particular, the active and exciting area of muonium chemistry is left to a future volume. The group of papers in section I addresses the physics of strongly correlated electrons in solids, one of the most active fields of condensed matter research today. Strong electron correlations arise from (Coulomb) interactions which render Landau's theory of electron transport for weakly interacting systems invalid. Included in this category are unconventional heavy-fermion superconductors, high-temperature copper-oxide superconductors, non-Fermi liquid (NFL) systems and systems with strong electron-lattice-spin coupling, such as the colossal magnetoresistance manganites. Two key properties often make the muon a unique probe of these materials: (1) the muon's large magnetic moment (~3 μp) renders it extremely sensitive to the tiny magnetic fields (~1 Gauss) found, for example, in many NFL systems and in superconductors possessing time-reversal-violating order parameters, and (2) the muon's spin 1/2 creates a simple μSR lineshape (no quadrupolar coupling), ideal for measuring spin-lattice-relaxation, local susceptibilities and magnetic-field distributions in ordered magnets and superconductors. Section II contains studies which exploit the unique sensitivities of μSR just noted to elucidate new and hidden properties of novel magnetic materials, including the use of very low energy muons to study thin films. Sections I and II are concerned with the bare positive muon as a probe of internal magnetic fields in metals. The papers in section III describe studies which exploit the fact that in semiconductors the muon appears as a light isotope of the hydrogen atom, called muonium. These studies provide important new information regarding the electronic structure and motion of light, dilute hydrogen-like impurities in semiconductors, which is useful for both semiconductor fundamentals and applications. Finally, in section IV experiments which probe electron transfer in large molecular systems are presented, including future prospects for investigating some materials of biological interest. These latter experiments exploit the sensitivity of muonium to the motion of electrons inside molecular systems, the so-called `labeled-electron' method. It is our hope that even this limited perspective shows the extraordinary degree to which the μSR technique is contributing deeply to our understanding of condensed matter physics. Richard Garwin's early experiments have indeed borne unexpected fruit! The editor is very grateful to all the invited authors for their timely contributions to this special section of Journal of Physics: Condensed Matter.

A recent paper [R. H. Silsbee, Phys. Rev. B 63, 155305 (2001)] presented a phenomenological theory for experiments of Hammar et al. [Appl. Phys. Lett. 79, 2591 (2001)] probing the non-equilibrium spin polarization in a two-dimensional electron gas induced by an electric current. This paper develops a relation between the "potentiometric signal" and the "diode signal" in those experiments.

Summary form only given. A single spin will not reverse its magnetic moment under a magnetic field without energy dissipation. However, a group of coupled spins could in certain situations by transforming the magnetic potential energy to exchange energy and magnetostatic energy via spin wave generation. In this paper, we present a systematic micromagnetic study on magnetization reversal dynamics in patterned thin film elements as well as thin film write heads. The properties of the generated spin waves and time dependent mode dispersion will be discussed.

Summary form only given. Bragg diffraction of light from magnetostatic waves in yttrium iron garnet (YIG) film has been investigated in recent years as potential candidates for applications to high speed light deflectors and switches. On the other hand, Bragg diffraction of infrared laser light from spin waves has been studied for three decades and found to be a useful tool in research on magnetoelastic propagation. This paper presents experiments of the optical interaction with spin waves (magnetostatic, magnetoelastic, and /spl omega//2 spin waves) in longitudinally magnetized YIG single crystal slabs and thick films, based on the principle of the turning point in nonuniform internal magnetic field due to the effect of demagnetization.

We report on time-resolved optical investigations on the polarization and the spin dynamics in non-magnetic and magnetic self-assembled II VI semiconductor quantum dots. In case of CdSe/ZnSe quantum dots, no transient loss of polarization is found within the time scale of exciton recombination, if one excites the excitons strictly resonant in the quantum dot ground state with a laser pulse linearly polarized along the [110] or [1-10] crystal axes. This indicates a high temporal stability of the exciton state, which is a coherent superposition of spin-up and spin-down exciton states. Even after replacing some Cd atoms in the crystal matrix by magnetic ions Mn2+, the polarization is being conserved as long as the average Mn2+ concentration is about (formula available in paper)or less, despite the pronounced exchange interaction between the manganese ion spins and the carrier spins. In case of magnetic semiconductor quantum dots with a large concentration of (formula available in paper)ions, the spin spin interaction between charge carriers and manganese ions results in the formation of a quasi-zero dimensional ferromagnetically aligned spin complex, the exciton magnetic polaron. For (formula available in paper)Se quantum dots this transient spin alignment is directly evidence by a transient shift of the emission energy. We deduce a typical time constant of 125 ps at T = 2 K for the dynamical response of the magnetic ion spins.