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QUOKKA is a 40 m pinhole small-angle neutron scattering instrument in routine user operation at the OPAL research reactor at the Australian Nuclear Science and Technology Organisation. Operating with a neutron velocity selector enabling variable wavelength, QUOKKA has an adjustable collimation system providing source–sample distances of up to 20 m. Following the large-area sample position, a two-dimensional 1 m2 position-sensitive detector measures neutrons scattered from the sample over a secondary flight path of up to 20 m. Also offering incident beam polarization and analysis capability as well as lens focusing optics, QUOKKA has been designed as a general purpose SANS instrument to conduct research across a broad range of scientific disciplines, from structural biology to magnetism. As it has recently generated its first 100 publications through serving the needs of the domestic and international user communities, it is timely to detail a description of its as-built design, performance and operation as well as its scientific highlights. Scientific examples presented here reflect the Australian context, as do the industrial applications, many combined with innovative and unique sample environments.

The nature of providing sample environment equipment and support is constantly evolving, as new technologies and experimental techniques are developed. To remain at the cutting edge of neutron scat...

A system for positioning powder samples in top-loading cryofurnaces during neutron scattering experiments, while facilitating the successive delivery of gas doses at set temperatures to the sample, has been designed and tested. The positioning system is compatible with a Hiden Isochema IMI instrument as a gas-dosing platform, enabling gases to be delivered to the sample through a centrally located and thermally stabilized capillary line and valve. The positioning system separates into an upper and a lower section, with the lower section enabling the sample to be isolated and inserted into a glove box. This work describes the system using example neutron powder diffraction results obtained with this system in closed-cycle cryofurnaces.

The low-energy magnetic excitation from the highly Ca-doped quasi-one-dimensional magnet $\mathrm{SrC}{\mathrm{a}}_{13}\mathrm{C}{\mathrm{u}}_{24}{\mathrm{O}}_{41}$ was studied in the magnetic ordered state by using inelastic neutron scattering. We observed the gapless spin-wave excitation, dispersive along the $a$ and $c$ axes but nondispersive along the $b$ axis. Such excitations are attributed to the spin wave from the spin-chain sublattice. Model fitting to the experimental data gives the nearest-neighbor interaction ${J}_{c}$ as 5.4 meV and the interchain interaction ${J}_{a}=4.4\phantom{\rule{0.16em}{0ex}}\mathrm{meV}$. ${J}_{c}$ is antiferromagnetic and its value is close to the nearest-neighbor interactions of the similar edge-sharing spin-chain systems such as $\mathrm{CuGe}{\mathrm{O}}_{3}$. Comparing with the hole-doped spin chains in $\mathrm{S}{\mathrm{r}}_{14}\mathrm{C}{\mathrm{u}}_{24}{\mathrm{O}}_{41}$, which shows a spin gap due to spin dimers formed around Zhang-Rice singlets, the chains in $\mathrm{SrC}{\mathrm{a}}_{13}\mathrm{C}{\mathrm{u}}_{24}{\mathrm{O}}_{41}$ show a gapless excitation in this paper. We ascribe such a change from gapped to gapless excitations to holes transferring away from the chain sublattice into the ladder sublattice upon Ca doping.

Neutron powder diffraction experiments reveal that $\mathrm{C}{\mathrm{o}}_{4}\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{9}$ forms a noncollinear in-plane magnetic structure with $\mathrm{C}{\mathrm{o}}^{2+}$ moments lying in the $ab$ plane. The spin-wave excitations of this magnet were measured by using inelastic neutron scattering and soundly simulated by a dynamic model involving nearest- and next-nearest-neighbor exchange interactions, in-plane anisotropy, and the Dzyaloshinskii-Moriya interaction. The in-plane magnetic structure of $\mathrm{C}{\mathrm{o}}_{4}\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{9}$ is attributed to the large in-plane anisotropy, while the noncollinearity of the spin configuration is attributed to the Dzyaloshinskii-Moriya interaction. The high magnetoelectric coupling effect of $\mathrm{C}{\mathrm{o}}_{4}\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{9}$ in fields can be explained by its special in-plane magnetic structure.

A combined solution is presented for minimizing the safety hazards associated with closed cycle cryostats described by Swainson & Cranswick [J. Appl. Cryst.(2010),43, 206–210]. The initial solution is to install a vent tube with one open end deep inside the sample space and a pressure relief valve at the top. This solution works for either a cryogen or a cryogen-free (closed cycle) system. The second approach, which can be combined with the first and is applicable to cryogen-free cryostats, involves electrically interlocking the closed cycle refrigerator compressor to the sample space, so that the system cannot be cooled in the presence of a leak path to air.

Variability in the abrasive wear of PCD coatings on cemented WC substrates has been investigated. Six samples of PCD coated carbides were tested in a wear testing rig. The PCD coated element was used to turn an industry standard vitrified bonded corundum grinding wheel. The wear rate was measured as the weight loss of the cutting element per cubic metre of grinding wheel machined during the test. Two grades of cutting elements were observed. One grade had wear rates between 6 and 7.3 g/m³ but of the three poor quality samples, only one valid test was made realising wear rate of ~7,800 g/m³. The microstructures of the samples were studied using SEM, X-ray imaging, neutron diffraction and XRD. SEM images revealed differences in the volume percentage of diamonds in the two grades and the XRD scans highlighted the variable distribution of the diamond phase in the coating. Estimates of the residual stresses in a good and poor quality samples indicated significantly higher compressive stresses in the good quality versus poor quality coating. These results have revealed two extremes in the wear rates of these PCD coated carbides. It is suggested that the difference in diamond content between the two grades is not sufficient to account for the 3 orders-of-magnitude difference in the observed wear rates. However, the presence of intrusive veins of carbide material in the coatings, especially around the curved cutting tip, suggested that the macroscopic defects observed in the x-ray and SEM images were the major cause of the high wear rates in the poor quality sample.

Template synthesis of metal oxides can create materials with highly controlled and reproducible pore structures that can be optimized for particular applications. Zirconium titanium oxides (25:75 mol %) with three different pore structures were synthesized in order to relate polymer loading capacity to macropore architecture. Sol-gel chemistry was used to prepare the materials in conjunction with (i) agarose gel templating, (ii) no template, and (iii) stearic acid templating. The three materials possessed high surface areas (212-316 m(2) g(-1)). Surface modification was performed postsynthetically using propionic acid (a monomer), glutaric acid (a dimer), and three molecular weights of poly(acrylic acid) (2000, 100,000, and 250,000 g mol(-1)). Higher loading (mg g(-1)) was observed for the polymers than for the small molecules. Following surface modification, a perceptible decrease in surface area and mesopore volume was noted, but both mesoporosity and macroporosity were retained. The pore architecture had a strong bearing on the quantity and rate of polymer incorporation into metal oxides. The templated pellet with hierarchical porosity outperformed the nontemplated powder and the mesoporous monolith (in both loading capacity and surface coverage). The materials were subjected to irradiation with (60)Co gamma-rays to determine the radiolytic stability of the inorganic support and the hybrid material containing the monomer, dimer, and polymer. The polymer and the metal oxide substrate demonstrated notable radiolytic stability.

Diamond composite materials are classified as superhard and exhibit exceptional abrasive resistance. Cemented tungsten carbide tools with a thick coating of diamond composite material (PCD) are finding increased usage in materials cutting operations in manufacturing, mining, minerals, gas and petroleum exploration and civil construction industries. Two major advantages derived from these coated tools are: (a) increased wear resistance and hence increased life-span of these tools and (b) their proven ability to handle “difficult-to-machine” materials as well as high-strength, extremely abrasive materials such as quartz-rich rocks, granites and basalts. In this research, the variability of the wear resistance of PCD coated tungsten carbide is correlated with microstructural variations. A detailed study of the microstructure and distribution of phases was performed using SEM, cathodoluminescence (CL) imaging, direct x-ray imaging, Raman spectroscopy as well as residual stress measurements using neutron diffraction.

Atomic force microscopy (AFM), X-ray magnetic circular dichroism (XMCD), magnetic force microscopy (MFM) and vibrating sample magnetometry (VSM) have been used to measure the magnetic and geometrical characteristics of triangular-shaped Co structures of lateral size 730 nm and thickness 32 nm, prepared by nanosphere lithography (NSL). Evidence of in-plane six-fold magnetic anisotropy induced by the symmetry of the structure has been found. By means of XMCD measurements, performed at remanence after applying a pulsed field, a structure rotation angle-dependent oscillation of about 15% with a periodicity of 60° has been observed for both the orbital and spin moments. Furthermore, the system exhibits the angular hysteresis effect. The magnetic measurements performed by MFM show a reduction of the magnetic configurations to only two states, one quasi-single domain Y state and second, a combination of vortex and Y state.

An almost linear relation between the Pt amount and the orbital to spin moment ratio (μl/μs) has been found in Cox Pt100–x nanoparticles prepared by vapour deposition and possessing a well defined chemically disordered crystallographic structure. X-ray magnetic circular dichroism (XMCD) measurements done at the L2,3Co edges show that a 4.0 nm, x = 100 Co reference sample has a ratio μl/μs = 0.097, comparable to values found for Co thin layers. An increase of the amount of Pt increases the μl/μs value: μl/μs = 0.11 for x = 78, μl/μs = 0.12 when x = 74 and finally, for x = 38 it becomes μl/μs = 0.140. Nanoparticles prepared by chemical synthesis with size proportional to changes of the stoichiometric ratio, from Co25Pt75 to Co50Pt50, show values of the orbital to spin moment ratio compatible with the trend found for the former ones. The samples prepared by chemical synthesis in a diameter range from 4 nm to 8 nm are characterized by a sharp size distribution of 10%. In contrast to the in situ prepared nanoparticles that are oxide free, however, they show a varying degree of surface oxidation depending on the ambient conditions they are exposed to. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Mass-filtered cobalt clusters with a size of 8 nm have been deposited in-situ under soft-landing conditions onto Au(111). The spin and orbital moments of the Co nanoparticles on a Au (111) single crystal have been investigated as a function of the temperature using the element-specific method of X-ray magnetic circular dichroism in photoabsorption. The results hint at an temperature-dependent spin-reorientation transition which is discussed with respect to different contribution to the magnetic anisotropy. Furthermore, by means of an in-situ oxidation experiment, the influence of an exposure to oxygen on the properties of the cobalt clusters has been investigated.

An extensive series of tetranuclear CuII2LnIII2 complexes [CuIILLnIII(hfac)2]2 (with LnIII being all lanthanide(III) ions except for the radioactive PmIII) has been prepared in order to investigate the nature of the CuII-LnIII magnetic interactions and to try to answer the following question: What makes the CuII2TbIII2 and CuII2DyIII2 complexes single molecule magnets while the other complexes are not? All the complexes within this series possess a similar cyclic tetranuclear structure, in which the CuII and LnIII ions are arrayed alternately via bridges of ligand complex (CuIIL). Regular SQUID magnetometry measurements have been performed on the series. The temperature-dependent magnetic susceptibilities from 2 to 300 K and the field-dependent magnetizations from 0 to 5 T at 2 K have been measured for the CuII2LnIII2 and NiII2LnIII2 complexes, with the NiII2LnIII2 complex containing diamagnetic NiII ions being used as a reference for the evaluation of the CuII-LnIII magnetic interactions. These measurements have revealed that the interactions between CuII and LnIII ions are very weakly antiferromagnetic if Ln=Ce, Nd, Sm, Yb, ferromagnetic if Ln=Gd, Tb, Dy, Ho, Er, Tm, and negligible if Ln=La, Eu, Pr, Lu. With the same goal of better understanding the evolution of the intramolecular magnetic interactions, X-ray magnetic circular dichroism (XMCD) has also been measured on CuII2TbIII2, CuII2DyIII2, and NiII2TbIII2 complexes, either at the L- and M-edges of the metal ions or at the K-edge of the N and O atoms. Last, the CuII2TbIII2 complex exhibiting SMM behavior has received a closer examination of its low temperature magnetic properties down to 0.1 K. These particular measurements have revealed the unusual very slow setting-up of a 3D order below 0.6 K.

Magnetization reversal of thin Fe, Co and Ni layers deposited on single-crystalline layers of V2O3 is shown to be governed by various contributions to the magnetic anisotropy of the ferromagnetic layers, which reflect the sensitivity of the systems to the crystallographic and magnetic moment orientation or the structural morphology of the interfaces. The complex behaviour observed is related to the rich phase diagram of the oxide, which undergoes a transition from a paramagnetic metallic to an insulating antiferromagnetic phase as the temperature is decreased to below ∼150 K. Focussing on the anisotropy contributions that result from the exchange interaction across the interface with antiferromagnetic V2O3, we have found a remarkable behaviour of the Fe overlayers which grow in a textured BCC(1 1 0) structure. The exchange anisotropy, probed as a bias of the ferromagnetic hysteresis loops for field-cooled samples, is absent for the interface with the ( 1 1 2 ¯ 0 ) surface of antiferromagnetic V2O3, but exists for the interface with the V2O3 (0 0 0 1) surface. This points to a very different electronic interaction at the two interfaces. The behaviour is at variance with what is observed for the Co and Ni overlayers which show an exchange anisotropy for both surfaces of the oxide. Measurements of X-ray magnetic circular dichroism reveal the presence of a magnetically dead layer in Fe at the interface with V2O3 ( 1 1 2 ¯ 0 ) . It is likely to disrupt the exchange coupling, and thus may be at the origin of the missing exchange anisotropy of Fe on this surface. The different evolution of the spin magnetic moment of Fe with the overlayer thickness suggests a different growth morphology on the two surfaces of the oxide. As a result of the interaction with Fe, the V2O3 layers acquire a small magnetic polarization at the interface at room temperature for both orientations.

The magnetization of ultrathin Fe deposited in situ onto a V(1 1 0) single crystal has been studied by means of X-ray magnetic circular dichroism measurements at the L 2,3 absorption edges of Fe and V as a function of the Fe coverage. The Fe magnetization sets on at an Fe thickness of 2 ML in accordance with an earlier Polarized Neutron Reflectometry investigation. It increases rapidly with Fe thickness and asymptotically reaches the bulk magnetization at 5 ML. In the critical Fe thickness regime between 2 and 5 ML it significantly increases by cooling from room temperature to 110 K due to the reduced Curie temperature of the ultrathin Fe film. In contrast, the onset of the Fe magnetization at 2 ML is barely influenced by cooling which may be due to the coalescence of the Fe islands observed earlier with low-energy electron diffraction. Residual O contamination on the V surface reduces the Fe magnetization due to the formation of Fe oxide.

The properties of the interface between a thin layer of native SiO 2 and a low molecular compound were studied by means of ultraviolet photoelectron spectroscopy (UPS). The investigated material, an amphiphilic derivative of 2,5-diphenyl-1,3,4-oxadiazole (NADPO), was prepared by using the Langmuir–Blodgett (LB) technique. It is of interest since its electronic properties do not depend on the preparation conditions and it is also being candidate for use in optoelectronic devices. The UPS measurements were performed at the beam line Seya F2.2 at HASYLAB (Hamburg, Germany). This beamline is of a 1 m Seya–Namioka monochromator type, equipped with two gratings, which cover the photon energy range from 4 to 40 eV. The photoelectrons were collected with a Vacuum Generators ADES 400 angle resolving spectrometer system at room temperature. The base pressure during the experiment was 1×10 −10 mbar. We investigated the interface properties depending on the number of monolayers (2, 4, 6 and 8) of well oriented LB films, monitoring the highest occupied molecular orbital (HOMO) energy position.

Electronic structure at the interface between gold and aromatic 1,3,4-oxadiazoles was studied by means of ultraviolet photoelectron spectroscopy (UPS). Thin films of 1,3,4-oxadiazoles were prepared in situ by evaporation from pinhole sources on freshly prepared gold on a Si substrate. We determine the frontier orbitals positions at the interface oxadiazoles/Au finding evidence for the presence of a dipole layer. Furthermore, the complete valence electronic band structure has been determined from the UPS spectra. The spectral features corresponding to the top of the valence band and dominating the electronic properties of this material were assigned to the different molecular eigenstates by comparison with simulated spectra from quantum chemical calculations.

Thermally stimulated luminescence (TSL), and ultraviolet photoelectron spectroscopy (UPS) measurements have been carried out on Langmuir–Blodgett films of a substituted 1,3,4-oxadiazole. UPS provided the experimental electronic band structure of the investigated material and also parameters like ionisation potential, 7.9 eV, and electron affinity, 4.8 eV. These high values indicate that it can be used as hole blocking/electron transporting layer in emitting devices. Thermally stimulated processes on oxadiazoles thin films have been studied in order to get information about their electronic properties. The fractional glow technique, applied on the thermal stimulated luminescence curves, highlights different peaks. They originate from carrier relaxation processes. We focused our attention on the complex structure between 120 and 160 K. By the analysis of the curves performed both with the initial rise method and with a fitting procedure, we estimated the activation energy, between 3.5 (initial rise method) and 4 meV (numerical simulation), the frequency factors, 104 s−1, and a Gaussian trap distribution shape.

The family of substituted 1,3,4-oxadiazole can be used in organic light-emitting diodes (OLEDs) acting both as hole blocking and as improved emissive layers. Thin films of aromatic 1,3,4-oxadiazoles, prepared in situ by evaporation from pinhole sources onto fresh deposited gold films on flat silicon wafers, were studied by means of ultraviolet photoelectron spectroscopy (UPS) in order to get detailed information about valence electronic band structure. The UPS measurements were performed at the beam line TGM-2 at BESSY (Berlin) in the energy range between 8 and 80 eV. Furthermore, we determined the vacuum level shift at the organic/metal interface. We used semi-empirical quantum-chemical calculations to evaluate the valence electronic structure of the isolated molecules. This was also the starting point used as input to simulate the UPS spectra obtained from the films. The good agreement between experimental and theoretical curves allows us to assign the different peaks to different molecular eigenstates and it also provides a more quantitative description of the experimental findings.

The dynamical phase transition mechanism of $({\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}){\mathrm{TiO}}_{3}$ (NBT) was studied using inelastic neutron scattering. Softening was observed of multiple phonon modes in the phase transition sequence of NBT. As usual, the softening of the zone center transverse optical modes ${\ensuremath{\Delta}}_{5}$ and ${\ensuremath{\Sigma}}_{3}$ was observed in the (200) and (220) zones, showing the Ti vibration instabilities in ${\mathrm{TiO}}_{6}$ octahedra for both cubic-tetragonal (C-T) and tetragonal-rhombohedral (T-R) phase transitions. In these two phase transitions, however, ${\mathrm{Ti}}^{4+}$ has different preferential displacement directions. Surprisingly, the longitudinal optic mode also softens significantly toward the zone center in the range of the transition temperature, indicating the ${\mathrm{Na}}^{+}/{\mathrm{Bi}}^{3+}$ vibration instability against ${\mathrm{TiO}}_{6}$ octahedra during the T-R phase transition. Strong inelastic diffuse scattering shows up near $M$(1.5, 0.5, 0) and $R$(1.5, 1.5, 0.5) in the tetragonal and rhombohedral phases, respectively, indicating the condensations of the ${M}_{3}$ and ${R}_{25}$ optic modes for the corresponding transitions. This reveals the different rotation instabilities of ${\mathrm{TiO}}_{6}$ in the corresponding transition temperature range. Bottleneck or waterfall features were observed in the dispersion curves at certain temperatures but did not show close correlations to the formation of polar nanoregions. Additional instabilities could be the origin of the complexity of phase transitions and crystallographic structures in NBT.

Spectroellipsometry represents a powerful technique in non-destructive and contactless material characterization. In this paper, using the above mentioned spectroellipsometric technique, we measure the refractive index profile of wet thermal SiO2 films on single-crystal silicon substrate under various thermal oxidation conditions. The optimum conditions for an accurate evaluation of the thin films parameters – refractive index and thickness – are determined. The effect of different oxidation conditions upon these parameters are further investigated.

The electronic structure of thin films of new heterocyclic compounds was studied by means of ultraviolet photoelectron spectroscopy (UPS) and near edge X-ray absorption fine structure (NEXAFS). The complete one-dimensional valence electronic band structure has been determined from the UPS spectra. The spectral features that correspond to the top of the valence band and that dominate the electronic properties of this material were assigned to the different molecular eigenstates by comparison with simulated spectra from quantum chemical calculations. NEXAFS measurements were carried out on the same films.

In 1998, prompted by the pioneering efforts of Prof Michael Meiβner, sample environment teams from different facilities started a series of biennial international workshops with the aim to discuss ...

Electronic band structure of three heterocyclic model compounds: 5,12-dihydro-quinoxalino-2,3-b-phenazine; 7,18-dihydro-5,7,11,16,18,20,22-octa-aza-nonacene; and 1,3,5-Tris[(3-phenyl-6-tri-fluoro-methyl)-quinoxaline-2-yl]benzene was studied by ultraviolet photoelectron spectroscopy. We also determined their ionisation potential, between 5.3 and 6.0 eV, suggesting that these materials can efficiently act as electron transporting layer in organic light emitting devices (OLEDs).

We studied ultraviolet photoelectron spectroscopy (UPS) and thermally stimulated processes in two types of phenylquinoxalines, and one type of starburst trisphenylquinoxaline in order to characterize the valence band structure and the localized states. An ionization potential of about 6.0 eV was determined for each material using UPS. Thermally stimulated discharge currents (TSDC) gave evidence of dipolar and/or charge transport mechanisms. We assigned each TSDC peak to the different elementary processes using in addition dielectric spectroscopy (DES), and from thermally stimulated luminescence (TSL) curves, performed for the first time on these materials, we estimated the mean trap depths.

Monodisperse mesoporous anatase titania beads with high surface areas and tunable pore size and grain diameter have been prepared through a combined sol-gel and solvothermal process in the presence of hexadecylamine (HDA) as a structure-directing agent. The monodispersity of the resultant titania beads, along with the spherical shape, can be controlled by varying the amount of structure-directing agent involved in the sol-gel process. The diameter of the titania beads is tunable from approximately 320 to 1150 nm by altering the hydrolysis and condensation rates of the titanium alkoxide. The crystallite size, specific surface area (from 89 to 120 m(2)/g), and pore size distribution (from 14 to 23 nm) of the resultant materials can be varied through a mild solvothermal treatment in the presence of varied amounts of ammonia. On the basis of the results of small-angle XRD, high-resolution SEM/TEM, and gas sorption characterization, a mechanism for the formation of the monodisperse precursor beads has been proposed to illustrate the role of HDA in determining the morphology and monodispersity during the sol-gel synthesis. The approach presented in this study demonstrates that simultaneous control of the physical properties, including specific surface area, mesoporosity, crystallinity, morphology, and monodispersity, of the titania materials can be achieved by a facile sol-gel synthesis and solvothermal process.

Using the spectroscopies based on x-ray absorption, we have studied the structural and magnetic properties of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}\mathrm{O}$ films ($x=0.1$ and 0.25) produced by reactive magnetron sputtering. These films show ferromagnetism with a Curie temperature ${T}_{C}$ above room temperature in bulk magnetization measurements. Our results show that the Co atoms are in a divalent state and in tetrahedral coordination, thus substituting Zn in the wurtzite-type structure of ZnO. However, x-ray magnetic circular dichroism at the $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}{L}_{2,3}$ edges reveals that the $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}3d$ sublattice is paramagnetic at all temperatures down to $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, both at the surface and in the bulk of the films. The $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}3d$ magnetic moment at room temperature is considerably smaller than that inferred from bulk magnetization measurements, suggesting that the $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}3d$ electrons are not directly at the origin of the observed ferromagnetism.

Co–Pt and Co nanoparticles (∼2 nm diameter) of different composition and crystal structure have been studied by X-ray magnetic circular dichroism (XMCD) at the Co L 2,3 edges. The magnetic properties of the samples, covered with a thin protecting layer of Al 2 O 3 , depend upon the composition, order and presence of Co oxide contamination. Pure Co nanoparticles reveal an orbital-to-spin moment ratio, μ l / μ s =0.13 at room temperature (RT) and μ l / μ s =0.11 at 3.4 K, Co/Pt mixed nanoparticles show a temperature independent μ l / μ s ratio: 0.13 both at RT and at 3.4 K. In contrast, Pt-shell Co-core samples have a ratio μ l / μ s =0.14 at RT and a strongly enhanced ratio μ l / μ s =0.20 at 3.4 K. The same samples with a small CoO contamination show an enhanced μ l / μ ss =0.25 at RT and μ l / μ ss =0.28 at 3.4 K. In the reversed configuration (Pt-core and a Co-shell), where the CoO is probably not at the Co–Pt interface but at the Co surface, the enhancement of μ l / μ s caused by the simultaneous increases of the orbital moment and decreases of the spin moment reaches a record value of μ l / μ ss =0.33 at 3.4 K and μ l / μ ss =0.21 at RT.

Extended X ray absorption fine structure EXAFS data and magnetic EXAFS MEXAFS data were measured at two temperatures 180 K and 296 K in the energy region of the overlapping L edges of bcc Fe grown on a V 110 crystal surface. In combination with a Bayes Turchin data analysis procedure these measurements enable the exploration of local crystallographic and magnetic structures. The analysis determined the atomic like background together with the EXAFS parameters which consisted of 10 shell radii, the Debye Waller parameters, separated into structural and vibrational components, and the third cumulant of the first scattering path. The vibrational components for 97 different scattering paths were determined by a two parameter force field model using a priori values adjusted to Born von Karman parameters of inelastic neutron scattering data. The investigations of the system Fe V 110 demonstrate that the simultaneous fitting of atomic background parameters and EXAFS parameters can be performed reliably. Using the L2 and L3 components extracted from the EXAFS analysis and the rigid band model, the MEXAFS oscillations can only be described when the sign of the exchange energy is changed compared to the predictions of the Hedin Lundquist exchange and correlation functional

The ex situ preparation of chemically synthesized cobalt nanoparticles leads unavoidably to particles coated with organic surfactants and a thin CoO shell. Argon ion $({\mathrm{Ar}}^{+})$ etching is a method often used to remove the surfactant and the oxide shell. Ex situ prepared nanoparticles of $9.7\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ diameters were investigated as a function of the sputtering time, by means of soft x-ray absorption spectroscopy at the C and O K edges and at the Co ${\mathrm{L}}_{2,3}$ edges. Low-energy $(500\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ ${\mathrm{Ar}}^{+}$ ion etching was effective in removing the organic coating layer of the nanoparticles, while much higher energy and longer sputtering times were required to affect the CoO shell. On the other hand, only a short time using low-energy hydrogen ion $({\mathrm{H}}^{+})$ etching was necessary to completely reduce the oxide shell. Magnetic circular dichroism of soft x-rays was used to measure the magnetic properties of the etched samples. We found that the orbital to spin magnetic moment ratio, ${\ensuremath{\mu}}_{l}∕\ensuremath{\mu}_{s}{}^{\mathrm{eff}}$, increases as a function of the ${\mathrm{Ar}}^{+}$ etching time. Such an increase may be ascribed to the incomplete removal of the CoO shell as well as to surface strain, increased roughness, and an effective reduction of the particle size induced by the high-energy ion etching. A much smaller effect was observed for the low-energy $(500\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ and short time ${\mathrm{H}}^{+}$ etched samples, where the magnetic moment ratio after the reducing procedure ${\ensuremath{\mu}}_{l}∕\ensuremath{\mu}_{s}{}^{\mathrm{eff}}=0.12$ is comparable to values obtained for bulk cobalt.

The properties of the interface Si /SiO 2 /low molecular compound were studied by means of ultraviolet photoelectron spectroscopy (UPS). The investigated material, an amphiphilic derivative of 2,5-diphenyl-1,3,4-oxadiazole (NADPO), is also of interest in photonics, because it can be used as active material in opto-electronic or electro-optic devices. The UPS measurements were performed at the beam line Seya F2.2 in HASYLAB (Hamburg, Germany). The photoelectrons were collected with a Vacuum Generators ADES 400 angle resolving spectrometer system at room temperature. The photoelectron spectra were measured with an angle of incidence of 45 degrees in normal emission for various incident energies and for an incident photon energy, E inc , of 24 eV in off normal emission. We investigated the interface properties depending on the number of monolayers (2, 4, 6, 8) of well oriented Langmuir-Blodgett films, monitoring the frontier orbital position, with particular regard to the highest occupied molecular orbital energy position. The obtained results give evidence that the band structure is depending on the thickness of the organic layer at the interface Si /SiO 2 /NADPO. We also monitored the development of the energetic position of the highest occupied molecular orbital (HOMO) from that of the monolayer towards the "true" HOMO energy position of the thin film, where the word "true" is related to the actual interface properties of the films and not to a single monolayer (ML) or a double layer. As a matter of fact the 2 ML spectra show a different behaviour than those of thicker films since the 2 ML system is strongly influenced by the substrate while the spectra of thicker films are de-coupled from the electronic structure of the substrate.

Quinoxaline model compounds are interesting materials for Organic Light Emitting Devices (OLEDs) because of their thermal stability and their higher ionization potential in comparison to other electron transporting/hole blocking materials. In this work we studied a starburst trisphenylquinoxaline by means of Ultraviolet Photoelectron Spectroscopy (UPS) and Thermally Stimulated Luminescence (TSL). UPS provided not only the characterization of the valence band structure but also parameters like ionization potential, 6 eV, and, combined with absorption spectroscopy, electron affinity, that are of crucial importance in designing optimized OLED configurations. On the other hand, a wide distribution of localized states occurs in organic layers due to several factors and TSL can investigate these states. The combination of the used techniques together with semi-empirical quantum chemical calculation, gave a detailed description not only of the valence and conduction band of the studied materials, i.e. the energy position of HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), but also of the trap distributions localized in the band gap: a shallow one at 0.06 eV and a deeper state centered at 0.24 eV. The full spectroscopic and electrical characterization of the material formed the background for understanding its behavior in heterolayer devices.

Electronic structure of ordered films obtained from an amphiphilic substituted 2,5-diphenyl- 1,3,4-oxadiazole (NADPO-11) by Langmuir-Blodgett (LB) technique were studied, for the first time, by means of ultraviolet photoelectron spectroscopy (UPS). The complete one- dimensional valence band structure has been determined from the UPS spectra. The spectral features that correspond to the top of the valence band and that dominate the electronic properties of this material were assigned to the different molecular eigenstates by comparison with simulated spectra from quantum chemical calculations. Good agreement between simulated and experimental curves allowed to assign UPS peaks to certain groups of molecular orbitals (MOs) and to understand the electronic bonding state (σ- or π- type) of the involved MOs. Furthermore, we performed UPS measurements on in-situ evaporated amorphous films of the same substance, comparing their valence band features to the previous ones. The correlation between ionisation potential and electron affinity, determined by combined ultraviolet photoelectron spectroscopy/optical spectroscopy, and carrier-transport and light emitting properties of these material are also discussed.

One approach to increase the overall performance of organic light emitting devices is to separate the light-emitting volume from the ones which are assigned to charge injection or transport. We realized such polymer hetero-layer structures by combination of hole transporting materials like polyparaphenylenevinylene (PPV) with new electron transporting materials, i.e. heterocyclic polymers and heterocyclic low molecular compounds, especially phenyl quinoxalines (PQs). The electronic properties of these heterocyclic compounds have been investigated by various methods including ultraviolet photoelectron spectroscopy. PQs show electron affinities near 3.5 eV and ionization potentials below 6 eV. Measurements of thermally stimulated depolarization currents (TSDC) were carried out in order to study both dipolar relaxation and charge transport processes in single layer devices. The TSDC spectra revealed the prominence of both dipolar relaxation and of charge transport processes. The dipolar processes show activation energies between 0.4 eV and 1 eV which are typical values for small relaxing entities like polymer side groups. Current-voltage and current-luminance characteristics were used to study the prepared heterolayer devices. Double layers made of PPV and polyphenylquinoxaline (PPQ) are characterized by low onset voltages near 2 V and high luminous efficiency of more than 0.8 cd/A. The experimental findings show that PPQs are promising materials in the field of organic electroluminescence.

Thermally stimulated processes on films of polyphenylquinoxalines (PPQs) and trisphenylquinoxalines (TPQs), materials suitable for electron transport/hole blocking layers on organic light-emitting devices (OLEDs), have been studied in order to get information about their electronic properties. By using thermally stimulated luminescence (TSL) curves, we estimated the mean trap depths.

Thin films of oxadiazoles and quinoxalines model compounds have been investigated by means of Ultraviolet Photoelectron Spectroscopy (UPS) in order to get a detailed description of the valence electronic band structure. Furthermore, we used semi-empirical quantum-chemical calculations to evaluate the valence electronic structure of the isolated molecules. UPS spectra have been calculated by use of molecular eigenvalues and we assigned the different peaks to the different molecular eigenstates.

One approach to increase the overall performance of organic light emitting devices is to separate the light-emitting volume from the ones which are assigned to charge injection or transport. The electronic properties of model heterocyclic compounds, namely low molecular phenylquinoxalines and related derivatives, for electron transport layers have been investigated by Ultraviolet Photoelectron Spectroscopy. The ionization potentials of these materials have been determined.