This PDF file contains the front matter associated with SPIE Proceedings Volume 8461, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Spin noise spectroscopy can be an extraordinary efficient, all-optical and low-perturbing tool to study the equilibrium spin dynamics in semiconductors. However, great care is necessary for studying the spin dynamics in inhomogeneous quantum dot ensembles. First, we show measurements on the spin dynamics of localized holes in (InGa)As quantum dots ensembles. The experiments reveal a very slow longitudinal spin relaxation time T_l and a moderately slow transverse spin relaxation time T₂ * which results from the finite hyperfine interaction of the hole spins due to heavy-light hole mixing in (InGa)As quantum dots. The longitudinal spin relaxation rate shows a linear dependence on the probe intensity which suggests a linear extrapolation to zero intensity for the extraction of the intrinsic spin relaxation rate. However, calculations reveal that the intrinsic heavy-hole spin relaxation is easily shadowed in quantum dot ensembles by effects of finite absorption even if the majority of quantum dots is well out of resonance of the probe laser. For typical laser intensities and very long spin relaxation times, a linear extrapolation to zero intensity is therefore not allowed. What is more, the line shape of the spin noise spectra changes from Lorentzian to non-Lorentzian with increasing laser intensity which can be easily misinterpreted as an intrinsic non-exponential spin relaxation process.

We report Y₃Fe₅O₁₂ thickness dependence of spin pumping, spin current generation from magnetization dynamics, in magnetic insulator Y₃Fe₅O₁₂/metal Pt bilayer films. We prepared different thickness Y₃Fe₅O₁₂ films by the metal-organic decomposition method and measured the electromotive force due to the inverse spin Hall effect induced by the spin pumping in Y₃Fe₅O₁₂/Pt films. We found that spin-mixing conductance, or spin-pumping efficiency, Y₃Fe5O₁₂/Pt films constant for the different thickness is almost same in various Y₃Fe₅O12 thickness. This result is consistent with the prediction of the spin pumping; the spin-pumping efficiency is determined by the exchange interaction at the Y₃Fe₅O₁₂/Pt interface. Keywords: Spintronics, Spin pumping, Spin current, Inverse spin Hall effect

The field of semiconductor spintronics has pursued the development of novel device architectures exploiting the spin degree of freedom in addition to, or in place of, traditional charge based functionality. In particular, theoretical modeling has predicted that the addition of a magnetic base layer to a bipolar junction transistor has the potential to serve as an exceptionally efficient spin filter, add intrinsically non-volatile functionality and exhibit extremely fast switching. Here, we present the experimental implementation of this scheme via the inclusion of a digitally-doped (Ga,Mn)As layer into the p region of an n-p-n III-As heterojunction bipolar transistor. These proof of principle devices exhibit gain greater than one, concurrent with robust ferromagnetism, which demonstrates a critical step in the development of an active spin functional device architecture.

In order to understand some new spintronics experiments of spin-dependent voltage for which the electric conduction does not play a role, a model of two spin-conduction channel is proposed in which the ferromagnets (either electric conductors or insulators) are defined by an ensemble of non­ equilibrium heat carriers composed of a populations of heat carriers of spin up, and heat carriers of spin down. It is shown that a temperature gradient generates locally a spin-accumulation. The diffu­ sion equation of this thermal spin-accumulation is straightforwardly derived from the corresponding transport equations and conservation equations. The principle of the detection is described in terms of Spin-Nernst effect.

We describe the applications of first-principles calculations to the analysis of transport and magnetic properties of rare-earth materials. The first application is a detailed calculation of the spin-disorder resistivity of heavy rare-earth metals in the Gd-Tm series. The crystallographic anisotropy of the spin-disorder resistivity agrees well with experiment, but its magnitude is significantly underestimated. Possible origins of this discrepancy are discussed. In the second part we analyze the exchange interaction in Gd-doped EuO using a magnetostructural cluster expansion based on the ab initio total energies. The calculated Curie temperature has a broad maximum extending over 10-20% Gd concentration and reaching approximately 150 K.

An investigation of barrier breakdown in MgO based Magnetic Tunnel Junctions submitted to pulsed electrical stress is presented. By studying the effect of delay between successive pulses, we observed that a very pronounced optimum in endurance of MTJs is obtained for an intermediate value of the delay between pulses corresponding to the characteristic time for a trapped electron in the barrier to escape from its trap. A charge trapping-detrapping model was proposed which consistently explains our experimental data. The delay between successive pulses affects the density of electrons trapped in the barrier. The average value in time and the time-modulation of the density of trapped charge give rise to distinct breakdown mechanisms. Our model allows evaluating the MTJ probability of breakdown for different applied pulse conditions. An expected endurance of the MTJs is then derived depending on the characteristics of the electrical stress in terms of delay, amplitude, unipolarity versus bipolarity. In a second part, low-frequency (0–12 kHz) noise measurements were performed in order to correlate the electrical noise with the defect density in the barrier.

Studies of the spin filter properties of tunnel barriers consisting of the insulating ferromagnets, EuO and EuS have been conducted for many years, but detailed investigation and application of their properties has been restricted by difficulties associated with growth and stoichiometry. We have recently demonstrated a new insulating ferromagnetic material GdN and shown that GdN barriers are strongly spin-filtering and can be incorporated into superconducting tunnel junctions. S/Insulator/S tunnel junctions enable detailed investigation of the magnitude of non-tunnel (leakage) currents and the optimisation of the tunnel barrier. We show that our insulating ferromagnet devices have a very low zero-bias leakage, but that behaviour for higher bias voltages is strongly non-ideal. We will discuss the potential for such devices to be used as spin-sources for both conventional and superconducting spintronics.

We report the successful electrical creation of spin polarization in p-type Si at room temperature by using an epitaxial MgO(001) tunnel barrier and Fe(001) electrode. Reflection high-energy electron diffraction observations revealed that epitaxial Fe/MgO(001) tunnel contacts can be grown on a (2×1) reconstructed Si surface whereas tunnel contacts grown on the (1×1) Si surface were polycrystalline. Transmission electron microscopy images showed a more flat interface for the epitaxial Fe/MgO/Si compared to that of the polycrystalline structure. For the Fe/MgO/p-Si devices, the Hanle and inverted Hanle effects were clearly observed at 300 K by using a three-terminal configuration, proving that spin polarization can be induced in the Si at room temperature. Effective spin lifetimes deduced from the width of the Hanle curve were 95 ± 6 ps and 143 ± 10 ps for the samples with polycrystalline and epitaxial MgO tunnel contacts, respectively. The observed difference can be qualitatively explained by the local magnetic field induced by the larger roughness of the interface of the polycrystalline sample. The sample with epitaxial Fe/MgO tunnel contact showed higher magnitude of the spin accumulation with a nearly symmetric behavior with respect to the bias polarity whereas that of the polycrystalline MgO sample exhibited a quite asymmetric evolution. This might be attributed to the higher degree of spin polarization of the epitaxial Fe/MgO(001) tunnel contact, which acts as a spin filter. Our experimental results suggest that an epitaxial MgO barrier is beneficial for creating spins in Si.

The electronic band structure of graphene monolayer and bilayer in the presence of spin-orbit coupling and transverse electric field is analyzed emphasizing the roles of three complementary approaches: first-principles calculations, symmetry arguments and tight-binding approximation. In the case of graphene monolayer, the intrinsic spin-orbit coupling opens a gap of 24 µeV at the K(K´)-point. The dominant physical mechanism governing the intrinsic spin-orbit interaction originates from d and higher carbon orbitals. The transverse electric field induces an additional extrinsic (Bychkov-Rashba-type) splitting of typical value 10 µeV per V/nm. In the case of graphene bilayer; the intrinsic spin-orbit coupling splits the band structure near the K(K´)-point by 24 µeV. This splitting concerns the low-energy valence and conduction bands (two bands closest to the Fermi level). It is similar to graphene monolayer and is also attributed to d orbitals. An applied transverse electric field leaves the low-energy bands split by 24 µeV independently of the applied field, this is the interesting and peculiar feature of the bilayer graphene. The electric field, instead, opens a semiconducting band gap separating these low-energy bands. The remaining two high-energy bands are directly at K(K´)-point spin-split in proportion to the electric field; the proportionality coefficient is given by value 20 µeV. Effective tight-binding and spin-orbit hamiltonians describing graphene mono-and bi-layer near K point are derived from symmetry principles.

Understanding and controlling the spin dynamics in semiconductor heterostructures is a key requirement for the design of future spintronics devices. In GaAs-based heterostructures, electrons and holes have very different spin dynamics. Some control over the spin-orbit fields, which drive the electron spin dynamics, is possible by choosing the crystallographic growth axis. Here, (110)-grown structures are interesting, as the Dresselhaus spinorbit fields are oriented along the growth axis and therefore, the typically dominant Dyakonov-Perel mechanism is suppressed for spins oriented along this axis, leading to long spin depasing times. By contrast, hole spin dephasing is typically very rapid due to the strong spin-orbit interaction of the p-like valence band states. For localized holes, however, most spin dephasing mechanisms are suppressed, and long spin dephasing times may be observed. Here, we present a study of electron and hole spin dynamics in GaAs-AlGaAs-based quantum wells. We apply the resonant spin amplification (RSA) technique, which allows us to extract all relevant spin dynamics parameters, such as g factors and dephasing times with high accuracy. A comparison of the measured RSA traces with the developed theory reveals the anisotropy of the spin dephasing in the (110)-grown two-dimensional electron systems, as well as the complex interplay between electron and hole spin and carrier dynamics in the two-dimensional hole systems.

We studied spin properties of Ge heterostructures by optical orientation and Hanle measurements. The circular polarization of the direct gap photoluminescence is shown to exceed the theoretical bulk limit, yielding about 37% and 85% for transitions with heavy and light holes, respectively. The energetic proximity of Γ and L valleys and ultrafast scattering of electrons from Γ to L states allowed us to resolve the spin dynamics of holes and to observe the polarization of electrons after scattering to L valleys. The spin relaxation analysis indicates that the spin lifetime of electrons exceeds 5 ns below 150 K, whereas it is in the 500 ps range for holes.

Voltage-driven spin transfer torques in magnetic tunnel junctions provide an outstanding tool to design advanced spin-based devices for memory and reprogrammable logic applications. The non-linear voltage dependence of the torque has a direct impact on current-driven magnetization dynamics and on devices performances. After a brief overview of the progress made to date in the theoretical description of the spin torque in tunnel junctions, I present different ways to alter and control the bias dependence of both components of the spin torque. Engineering the junction (barrier and electrodes) structural asymmetries or controlling the spin accumulation profile in the free layer offer promising tools to design effcient spin devices.

We report on microwave oscillations induced by spin-transfer-torque in metallic spin-valves obtained by electrodeposition of Co-Cu-Co trilayer structures in nanoporous alumina templates. Using micromagnetic calculations performed on similar spin-valve structures it was possible to identify the magnetization dynamics associated with the experimentally determined microwave emission. Furthermore it appears that in our particular geometry the microwave emission is generated by the vortex gyrotropic motion which occurs in, at least, one of the two magnetic layers of our spin-valve structures. Microwave emission was obtained in the absence of any external magnetic field with the appropriate magnetization configuration.

The magnetic vortex is the simplest, non-trivial ground state configuration of micron and sub-micron sized soft magnetic thin film platelets and therefore an interesting subject for the study of micro magnetism. Essential progress in the understanding of nonlinear vortex dynamics was achieved when low-field core toggling was discovered by excitation of the gyrotropic eigenmode at sub-GHz frequencies. At frequencies more than an order of magnitude higher vortex state structures possess spin wave eigenmodes arising from the magneto-static interaction. We demonstrated, experimentally and by micromagnetic simulations, that the unidirectional vortex core reversal process also occurs when azimuthal spin wave modes are excited in the multi-GHz frequency range. This finding highlights the importance of spin wave – vortex interaction and boosts vortex core reversal to much higher frequencies, which may offer new routes for GHz spintronics applications.

As conventional Silicon-based transistors reach their scaling limits, novel devices for performing computations have emerged as alternatives to continue the improvements in information technology that have benefited society over the past 40 years. One candidate that has shown great promise recently is a device that performs logical computations using dipole coupled nanomagnets. In this paper, we discuss recent advances that have led to a greater understanding of signal propagation in nanomagnet arrays. In particular, we highlight recent experimental work towards the imaging of a propagating magnetic cascade.

Until now, spintronics devices have relied on polarized currents, which still generate relatively high dissipation, particularly for nanodevices based on DW motion. A novel solution to further reduce power consumption is emerging, based on electric field (E) gating to control the magnetic state. Here, we will describe the state of the art and our recent experiments on voltage induced changes in the magnetic properties of ferromagnetic metals. A thorough description of the advances in terms of control of intrinsic properties such as magnetic anisotropy and ferromagnetic transition temperature as well as in intrinsic properties like coercive field and domain wall motion will be presented. Additionally, a section will be dedicated to the summary of the key aspects concerning the fabrication and performance of magneto-electric field-effect devices.

We show how the different spin polarized edge states of the two-dimensional topological insulator mercury telluride can be selectively switched within an elongated constriction. To this end, we derive an effective onedimensional Hamiltonian incorporating the confinement induced gap between right- and left-moving edge states, as well as an energy dependent effective spin-orbit interaction. By means of a transfer matrix approach, we study the transport properties based on this model Hamiltonian and reveal switching characteristics that can serve as the building block for a three state spin- and charge transistor based on a locally gated topological insulator constriction.

Introduction: It is now well recognized that energy dissipation in microchips may ultimately restrict device scaling – the downsizing of physical dimensions that has fuelled the fantastic growth of microchip industry so far. However, energy dissipation in electronic devices has even bigger consequences. Use of electronic equipments in our daily life is increasing exponentially. As a result, energy dissipation in electronic devices is expected to play an increasingly significant role in terms of national energy needs [1-6]. But there is a fundamental limit to how much the dissipation can be reduced in transistors that is in the heart of almost all electronic devices. Conventional transistors are thermally activated. A barrier is created that blocks the current and then the barrier height is modulated to control the current flow. This modulation of the barrier changes the number of electrons exponentially following the Boltzmann factor exp(qV/kT). This in turn means that to change the current by one order of magnitude at least a voltage of 2.3kT/q (that translates into 60 mV at room temperature) is necessary. In practice, a voltage many times this limit of 60 mV has to be applied to obtain a good ON current to OFF current ratio. Because this comes from the Boltzmann factor that is a fundamental nature of how electrons are distributed in energy, it is not possible to reduce the supply voltage in conventional transistors below a certain point, while still maintaining a healthy ON/OFF ratio that is necessary for robust operation. On the other hand, continuous down scaling is putting even larger number of devices in the same area thus increasing the energy dissipation density beyond controllable and sustainable limits. This has been termed as the Boltzmann’s Tyranny [2] and it has been predicted that unless new principles are found based on fundamentally new physics, the transistors will die a thermal death [4].

Spin-symmetry breaking in nanoscale structures caused by spin-orbit interaction, leading to a new branch in optics – spinoptics is presented. Spin-dependent plasmonics based on the interference of topological defects in the near-field was observed. We utilize the surface plasmons' scattering dynamics from localized vortex sources to create spinoptical devices as an ensemble of isolated nanoantennas to observe a "giant" spin-dependent plasmonic vortex, and a spin-dependent plasmonic focusing lens. Moreover, an observation of optical Rashba effect from spinoptical metamaterials consisting of nanoantennas is presented. The observed spin split dispersion arises from the inversion symmetry violation in the lattice. The observed effects inspire one to propose a new generation of optical elements for nano-photonic applications.

By superposing two electric fields of light excited by s- and p-polarized light, respectively, it is possible to break the symmetry of the field intensity distribution in plasmonic crystals, which results in a DC voltage normal to the plane of incidence. Experimental results on 40 nm–thick Au film with square array of holes with diameter of 240 nm and period of 500 nm are compared with a numerical calculation based on the fast multipole boundary integral equation method. Dispersive behavior of transverse voltage around the surface plasmon resonance for circularly polarized light is elucidated in terms of the phase shift at the resonance.

The angular momentum of light can be split into spin and orbital components. Only recently several optical processes involving a conversion of angular momentum from one form to another were conceived and experimentally demonstrated. We will briefly review these processes, and then survey some applications we have demonstrated of these spin-orbit effects in classical and quantum optics. Finally, we will show that analogous spin-orbit effects can be conceived for electron beams, leading to a theoretical proposal for a high-efficiency electron spin filter. If it will prove to be practical, this device could lead to a spin-polarized electron microscopy.

Spin related effects have been intensively studied using electrical transport methods, by measuring the spin diffusing length in metals and semiconductors. In addition to electrical transport, the thermoelectric properties of magnetic materials are increasingly gathering more attention. There, thermal magnons are expecting to play an major role. However, despite intensive studies on the spin transport, the coupling between electrons and magnons in ferromagnetic metals remains poorly known. Here, we demonstrate a conceptually new device that enables us to gather information on magnon–electron scattering and magnon-drag effects. The device resembles a thermopile formed by a large number of pairs of ferromagnetic wires placed between a hot and a cold source and connected thermally in parallel and electrically in series. By controlling the relative orientation of the magnetization in pairs of wires, the magnon drag can be studied independently of the electron and phonon drag thermoelectric effects. Measurements as a function of temperature reveal the effect on magnon drag following a variation of magnon and phonon populations. These results demonstrate the feasibility of directly converting magnon dynamics of nanomagnets into an electrical signal and could pave the way to novel thermoelectric devices for energy harvesting.

We present a methodology to systematically and analytically treat phonon-induced spin relaxation of conduction electron in silicon. All leading order contribution from all phonon modes and scattering processes are considered and the results for spin-flip matrix elements and spin lifetime are summarized. We show the explicit dependence of matrix elements on the electron wavevectors, spin orientation and phonon polarization. These results are shown to be powerful especially under symmetry-breaking conditions when an averaging rough evaluation of the matrix elements is not sufficient. Corrections due to the special two-band degeneracy in the X point (near the conduction valley minima) are also discussed. Numerical calculation are used to confirm the analytical results.

In this invited paper, we review some of our latest works on plasmonic antennas and their interactions with photonic angular momentum. As receiving antennas, both theoretical and experimental results reveal that spiral plasmonic antenna responds differently to photons with left-hand circular polarization and right-hand circular polarization. This spin degeneracy removal finds many potential applications including extremely small circular polarization analyzer for polarimetric imaging, parallel near field probes for optical imaging and sensing, nano-lithography and high density heat assisted magnetic recording. On the transmitter side, through coupling quantum dot nano-emitters to spiral plasmonic antenna, nano-scale spin photon sources with high directivity and circular polarization extinction ratio is demonstrated. Numerical modeling and experimental evidences also indicate that the emitted photons can be imprinted with the photonic spin angular momentum and orbital angular momentum information simultaneously via the interactions between photonic angular momentum and plasmonic antennas. These findings not only are useful for the fundamental understanding of the interaction between plasmonic antennas and photonic angular momentum but also illustrate the versatility of plasmonic antennas as building blocks for practical spin optics and quantum optics devices and systems.

We present a theoretical and experimental investigation of the spin Hall e®ect (SHE) of light in graphene. When a light beam impinges onto graphene-prism interface near Brewster angle, an enhanced and switchable spin- dependent splitting can be detected via the signal enhancement technique known from weak measurements. Our preliminary experimental results show that the SHE of light can become an advantageous metrology tool for characterizing the refractive index of graphene. In addition, the SHE of light may have a potential of probing the spatial accumulations of spin electrons in the graphene, which builds a bridge between electronic SHE and photonic SHE.

We report on spin-photodiodes based on fully epitaxial Fe/MgO/Ge(001) heterostructures for room temperature integrated detection of light helicity at 1300 nm and 1550 nm wavelengths. The degree of circular polarization of light determines the spin direction of photo-carriers in Ge that are filtered by the Fe/MgO analyzer. Spin-detection experiments are performed by measuring the photocurrent while illuminating the spin-photodiodes with left or right circularly polarized light, under the application of a magnetic field parallel to the light direction which drives the Fe magnetization out of plane. We found that the spin-photodiodes spin filtering asymmetry is reduced by ∼40% in forward bias and by less than 15% in reverse bias, when increasing the photon wavelength from 1300 nm to 1550 nm. This result, apparently counterintuitive because of the larger spin polarization of the photo-carriers generated at 1550 nm with respect to that at 1300 nm, is explained in terms of the different spatial profile of carrier generation inside Ge. The larger penetration depth of light at 1550 nm leads to a smaller polarization of photocarriers when they reach the MgO tunneling barrier, due to the more efficient spin relaxation during transport.

Recently, there has been growing interest in the field of organic spintronics, where the research on organic semiconductors (OSCs) has extended from the complex aspects of charge carrier transport to the study of the spin transport properties of those anisotropic and partly localized systems.¹ Furthermore, solution-processed OSCs are not only interesting due to their technological applications, but it has recently been shown in 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) thin film transistors that they can exhibit a negative temperature coefficient of the mobility due to localized transport limited by thermal lattice fluctuations.² Here, spin injection and transport in solution-processed TIPS-pentacene are investigated exploiting vertical CoPt/TIPSpentacene/AlO_x/Co spin valve architectures.³ The antiparallel magnetization state of the relative orientation of CoPt and Co is achieved due to their different coercive fields. A spin valve effect is detected from T = 175 K up to room temperature, where the resistance of the device is lower for the antiparallel magnetization state. The first observation of the scaling of the magnetoresistance (MR) with the bulk mobility of the OSC as a function of temperature, together with the dependence of the MR on the interlayer thickness, clearly indicates spin injection and transport in TIPS-pentacene. From OSC-spacer thickness-dependent MR measurements, a spin relaxation length of TIPS-pentacene of (24±6) nm and a spin relaxation time of approximately 3.5 μs at room temperature are estimated, taking the measured bulk mobility of holes into account.

The understanding of spin transport in organics has been challenged by the discovery of large magnetic field effects on properties such as conductivity and electroluminescence in a wide array of organic systems. To explain the large organic magnetoresistance (OMAR) phenomenon, we present and solve a model for magnetoresistance in positionally disordered organic materials using percolation theory. The model describes the effects of singlettriplet spin transitions on hopping transport by considering the role of spin dynamics on an effective density of hopping sites. Faster spin transitions open up `spin-blocked' pathways to become viable conduction channels and hence produce magnetoresistance. We concentrate on spin transitions under the effects of the hyperfine (isotropic and anisotropic), exchange, and dipolar interactions. The magnetoresistance can be found analytically in several regimes and explains several experimental observations

In this work we investigate carrier dynamics of narrow gap ferromagnetic alloys grown by MOVPE. We determine the intraband and interband relaxation times in these material systems where the samples are excited with photon energies above the band gap of InMnAs and InMnSb films. Our results are important for understanding the electronic states and the relaxation mechanisms in these ferromagnetic materials.

We report on combined theoretical and experimental studies of spin-split bands in semiconductors in magnetic fields. We have studied a wide range of systems including: 1) electron and valence band splitting in dilute magnetically doped semiconductors (DMS) systems like InMnAs, 2) electron and valence band splitting in strained InSb/AlInSb heterostructures and 3) valence band splitting in GaAs. The systems have been studied with a variety of experimental techniques including: i) ultra-high magnetic field cyclotron resonance ii) magnetoabsorption and iii) optically pumped NMR (OPNMR). Calculations are based on the 8-band Pidgeon-Brown model generalized to include the effects of the quantum confinement potential as well as pseudomorphic strain at the interfaces and sp-d coupling between magnetic impurities and conduction band electrons and valence band holes. Optical properties are calculated within the golden rule approximation and compared with experiments. Detailed comparison to experiment allows one to accurately determine conduction and valence band parameters including effective masses and g-factors. Results for InMnAs show shifts in the cyclotron resonance peaks with Mn doping. For InSb, we find a sensitive dependence of the elecronic structure on the strain at the pseudomorphic interfaces. For GaAs, we show that OPNMR allows us to spin-resolve the valence bands and that structure in the OPNMR signal is dominated by the weaker light hole to conduction band Landau level transitions.

In the present study, we have investigated the effect of 50 MeV Ag-ions irradiation on structural, optical and magnetic properties of pure ZnO, Zn_0.95V_0.05O and Zn_0.90V_0.10O thin films. X-ray diffraction (XRD) analysis of the films before and after ion irradiation confirms that all the films are in (002) preferred orientation. Upon ion irradiation, the increase of full width at half maximum (FWHM) and decrease of XRD intensity of (002) diffraction peak are observed. Photoluminescence (PL) spectra of ion irradiated films exhibit strong defect related emission about ~2.45 eV. It might be attributed to the defects such as oxygen vacancies in the film. The formation of oxygen vacancies upon ion irradiation resulting increase in band gap of pure ZnO, Zn_0.95V_0.05O and Zn_0.90V_0.10O thin films. The ion irradiated Zn_0.95V_0.05O and Zn_0.90V_0.10O films exhibit strong room temperature ferromagnetism as evidenced from VSM measurements. It is conclude that the spin associated with V ions together with increasing concentration of oxygen vacancies favours enhanced ferromagnetic behaviour in irradiated V doped ZnO films.

In the present study, we have investigated the surface functionalization of dodecanethiol on ZnO film surface grown at three different oxygen partial pressure using pulsed laser deposition (PLD) technique. The thiol funcitonalized ZnO films have been examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and vibrating sample magnetometer (VSM) measurement. XRD pattern show slight decrease in intensity of diffraction peak upon surface functionalization. The chemical bonding of ZnO with thiol has been confirmed by XPS measurement. The presence of S 2p_3/2 peak centered about 163 eV suggests that proton has dissociated fromed thiol and form chemical bonding to the ZnO surface. PL measurements of thiol functionalized ZnO films show quenching of visible emission intensity relative to the unfunctionalized ZnO films. The quenching of visible emission suggests that thiol passivates surface defects via Zn-S bonding. Surface functionalization of ZnO films with thiol induces robust room temperature ferromagnetism as evidenced from VSM measurements.

_{Cu-doped TiO2 anatase nanorods are obtained by annealing the hydrothermally synthesized Cu-doped titanate nanotubes precursor at temperatures 500 °C in different atmosphere (oxygen, air and argon). TEM image of the nanorods confirmed that the nanorods are randomly oriented with an average length of 100 nm and a mean diameter of 15–25 nm. X-ray diffraction ruled out the formation of either metallic Cu or copper oxide cluster and confirmed the intrinsic ferromagnetic nature. The photoluminescence (PL) spectrum analysis revealed that the ferromagnetism is due to the defects. The ferromagnetic order of Cu-doped TiO2 anatase nanorods is found to be greater in argon atmosphere than air. In the case of oxygen annealed sample least ferromagnetic ordering is found due to quenching of oxygen vacancies defects. The observed sequence of reduction in ferromagnetism shows a close inter-relationship with the behavior of oxygen vacancies..}