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The electronic state and the structural properties of the helical magneto-electric material Cu 2 OSeO 3 is investigated through temperature-dependent synchrotron based x-ray diffraction and x-ray absorption spectroscopy. The x-ray absorption spectra on Cu and Se- K edges indicate that Cu and Se ions are in the 2＋ and 4＋ charge states respectively. The pre-edge corresponding to K -line of Cu in the x-ray absorption spectra cannot be fitted using a single Lorentzian function. At least two different Lorentzian lines are required to fit the pre-edge, which are separated by ∼ 0. 6 ± 0. 042 eV. This separation originates due to the difference in the crystallographic environment of Cu(1) and Cu(2) and the subsequent difference in the energy of the 3 d orbitals of two Cu sites. The obtained energy difference reconfirms the value reported using resonant inelastic x-ray scattering and maximally localized Wannier function calculation. The synchrotron based powder x-ray diffraction indicates significant anomaly in the Cu-O-Cu bond angle around the magnetic transition temperature ( T C ∼ 59 K). Interestingly, the sample show negative thermal expansion in the lattice parameter below T C. Such anomalies can be connected to the exchange-striction mechanism. • Anomalous structural variation in a helical magneto-electric material Cu 2 OSeO 3. • Presence of exchange striction at the magnetic transition. • X-ray absorption spectroscopy indicates ＋2 and ＋4 ionic states of Cu and Se, respectively. • Multiple peak structure of the pre edge of x-ray absorption spectroscopy data corroborating two inequivalent positions of Cu. [ABSTRACT FROM AUTHOR]

Hydrodechlorination reaction of 3-(benzo-1,3-dioxol-5-yl)-3-chloro-2-methylacrylaldehyde in the presence of different low metal content heterogeneous mono- or bimetallic catalysts was tested for the synthesis of the fragrance Helional® (3-[3,4-methylendioxyphenyl]-2-methyl-propionaldehyde). In particular, mono Pd/Al2O3, Rh/Al2O3 or bimetallic Pd-Cu/Al2O3, Rh-Cu/Al2O3 catalysts were tested in different reaction conditions from which it emerged that mono-Rh/Al2O3 was the best performing catalyst, allowing achievement of 100% substrate conversion and 99% selectivity towards Helional® in 24 h at 80 °C, p(H2) 1.0 MPa in the presence of a base. To establish correlations between atomic structure and catalytic activity, catalysts were characterized by Cu, Rh and Pd K-edge XANES, EXAFS analysis. These characterizations allowed verification that the formation of Pd-Cu alloys and the presence of Cu oxide/hydroxide species on the surface of the Al2O3 support are responsible for the very low catalytic efficiency of bimetallic species tested. [ABSTRACT FROM AUTHOR]

Martensitic transition temperature steadily decreases in Ni 2− x Fe x Mn 1.5 In 0.5 and is completely suppressed at x = 0.2. Despite suppression of martensitic transition, Ni 1.8 Fe 0.2 Mn 1.5 In 0.5 does not display the expected strain glassy phase. Instead, a ground state with dominant ferromagnetic interactions is observed. A study of structural and magnetic properties of x = 0.2 reveal that the alloy consists of a major Fe rich cubic phase and a minor Fe deficient monoclinic phase favoring a ferromagnetic ground state. This is exactly opposite of that observed in Ni 2 Mn 1− y Fe y In 0.5 wherein a strain glassy phase is observed for y = 0.1. The change in site symmetry of Fe when doped for Ni in contrast to Mn in the Heusler composition seems to support the growth of the ferromagnetic phase. • Ni 1.8 Fe 0.2 Mn 1.5 In 0.5 despite impurity doping does not display strain glassy phase. • Ni 1.8 Fe 0.2 Mn 1.5 In 0.5 phase separates into major cubic ferromagnetic phase and minor martensitic phase. • Ground state of Ni 1.8 Fe 0.2 Mn 1.5 In 0.5 is exact opposite of strain glassy Ni 2 Mn 1.4 Fe 0.1 In 0.5. • Site symmetry of the dopant atoms plays a role in driving structural and magnetic interactions. [ABSTRACT FROM AUTHOR]

The β phase of tungsten has attracted great interest for spintronic applications due to its higher spin Hall angle compared to other elemental solids and large spin–orbit torque, but the stability of this phase is yet to be well understood as many different results are there in the literature mainly based on the film thickness, temperature, and overall growth conditions. The growth of films by sputter deposition has emerged as a promising technique to achieve β-W owing to its compatibility with current spintronic technology. We demonstrate here the efficient ability of dc magnetron sputtering to grow stable β-W films up to a thickness of ∼180 nm at room temperature by varying a set of deposition parameters like pressure, power, and deposition time and discuss the various underlying mechanisms. From these results, the optimized set of deposition parameters for growing β-W films is given. A clear understanding of the influence of oxygen in the atomic structure of β-W is obtained by varying the thickness of the films. This is confirmed from the ab initio molecular dynamics (MD) simulations, where the atomic structure is influenced by the oxygen doping concentration. A stable polycrystalline β phase can be achieved by controlled doping of oxygen. Additionally, a phase transformation from α to β with the doping of oxygen is also evident by MD simulations. [ABSTRACT FROM AUTHOR]

Dispersion of metal nanoparticles on flat surfaces has attracted considerable interest in many technological applications. Numerous advantages of functionalized patterned nanostructures especially in medical physics, chemistry, biology, and semiconductor quantum dot applications have rapidly driven the growth of this field in the last two decades. In particular, for applications involving biomedical imaging, the nanoparticles have attracted perhaps the greatest attention as these materials provide a direct interface at the subcellular length scale. Reliable characterization methods are thus often needed to infer their detailed structural properties such as average particle size, particle shape, internal structure, surface morphology, distribution of particles, and their chemical composition. As a nondestructive probe, X-ray fluorescence measurements at grazing incidence provide sensitive information about the physical and chemical nature of the nanoparticles over the large surface area of a substrate. Herein, we demonstrate the potential capabilities of the X-ray fluorescence technique for reliable and precise determination of surface morphology of metal nanoparticles, dispersed on a flat surface. Our results show that X-ray standing wave assisted fluorescence measurements are markedly sensitive to the nature of dispersion of nanoparticles on a substrate surface. We have analyzed different types of nanostructured materials; e.g. a W thin film structure and Au nanoparticles deposited on a Si surface. The average size of the Au nanoparticles estimated, using X-ray standing wave fluorescence analysis, was found to closely agree with the atomic force microscopy measurements. The inherent features of the X-ray fluorescence technique permit us to analyze distribution of all kinds of metal and metalloid nanoparticles on a flat surface. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper is a continuation and extension of our earlier work ( X-ray Spectrom. 2010, 39, 127-134, DOI:10.1002/xrs.1215) on the development of a software platform CATGIXRF, as a solution to provide non-destructive evaluation of nanostructured materials. Here, we describe an interactive graphical user interface (GUI) for the CATGIXRF program. The newly developed GUI interface facilitates determination of microstructural parameters on angstrom length scale for the nanostructured thin layered materials using synchrotron as well as laboratory X-ray sources. It allows combined analysis capabilities for both the X-ray reflectivity and grazing incidence X-ray fluorescence (GIXRF) data simultaneously, thus enabling us a greater sensitivity for the determination of microstructural parameters such as thickness, interface mixing, and roughness of a thin film medium with improved accuracies. The utility and various newly added salient features of the GUI-CATGIXRF program are described by providing example calculations as well as by analyzing experimentally a few thin film structures with different surface-interface properties. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Long-term durability of a thin film device is strongly correlated with the nature of interface structure associated between different constituent layers. Synthetic periodic multilayer structures are primarily employed as artificial X-ray Bragg reflectors in many applications, and their reflection efficiency is predominantly dictated by the nature of the buried interfaces between the different layers. Herein, we demonstrate the applicability of the combined analysis approach of the X-ray reflectivity and grazing incidence X-ray fluorescence measurements for the reliable and precise determination of a buried interface structure inside periodic X-ray multilayer structures. X-ray standing wave field (XSW) generated under Bragg reflection condition is used to probe the different constituent layers of the W-B4C multilayer structure at 10 keV and 12 keV incident X-ray energies. Our results show that the XSW assisted fluorescence measurements are markedly sensitive to the location and interface morphology of a buried layer structure inside a periodic multilayer structure. The cross sectional transmission electron microscopy results obtained on the W-B4C multilayer structure provide a deeper look on the overall reliability and accuracy of the XSW method. The method described here would also be applicable for nondestructive characterization of a wide range of thin film based semiconductor and optical devices. [ABSTRACT FROM AUTHOR]

The effect of longitudinal (or temporal) coherence on total reflection assisted x-ray standing wave (TR-XSW) analysis of nanoscale materials is quantitatively demonstrated by showing how the XSW fringe visibility can be strongly damped by decreasing the spectral resolution of the incident x-ray beam. The correction for nonzero wavelength dispersion (δλ ≠ 0) of the incident x-ray wave field is accounted for in the model computations of TR-XSW assisted angle dependent fluorescence yields of the nanostructure coatings on x-ray mirror surfaces. Given examples include 90 nm diameter Au nanospheres deposited on a Si(100) surface and a 3 nm thick Zn layer trapped on top a 100 nm Langmuir-Blodgett film coating on a Au mirror surface. Present method opens up important applications, such as enabling XSW studies of large dimensioned nanostructures using conventional laboratory based partially coherent x-ray sources. [ABSTRACT FROM AUTHOR]

A new multipurpose x-ray reflectometer station has been developed and augmented at the microfocus beamline (BL-16) of Indus-2 synchrotron radiation source to facilitate synchronous measurements of specular x-ray reflectivity and grazing incidence x-ray fluorescence emission from thin layered structures. The design and various salient features of the x-ray reflectometer are discussed. The performance of the reflectometer has been evaluated by analyzing several thin layered structures having different surface interface properties. The results reveal in-depth information for precise determination of surface and interface properties of thin layered materials demonstrating the immense potential of the combined measurements of x-ray reflectivity and grazing incidence fluorescence on a single reflectometer. [ABSTRACT FROM AUTHOR]

Total reflection X-ray fluorescence (TXRF) spectroscopy has seen remarkable progress over the past years. Numerous applications in basic and applied sciences prove its importance. The large spectral background, which is a major detrimental factor in the conventional X-ray fluorescence technique, limits the element detection sensitivities of the technique to the µg g-1 (ppm) range. This spectral background is reduced to a great extent in the TXRF technique due to the low extinction depth of the primary incident X-ray beam. In synchrotron radiation (SR) based TXRF measurements the spectral background is reduced further because of the polarization of the synchrotron X-ray beam. Here, we show in detail the influence of synchrotron polarization on the spectral background in a fluorescence spectrum and its significance towards TXRF detection sensitivities. We have performed TXRF measurements on standard reference materials to show that one obtains approximately one order of magnitude enhancement in the spectral signal strength by utilizing the anisotropic nature of the scattered synchrotron radiation in the horizontal detection geometry. [ABSTRACT FROM AUTHOR]

In this work, sol–gel ZnO thin films were implanted with Al ions of various fluences to study their electrical transport properties as transparent conducting oxide (TCO) layers. Additionally, formation of structural defects and modifications of the optical emission properties due to implantation have been investigated extensively to correlate the resultant electrical properties. By varying the ion fluence over two orders of magnitude from 1 × 1013 to 6 × 1015 ions/cm2, interestingly the electrical transport properties have been seen to be degraded in an unexpected manner as soon as Al is implanted and beyond a certain fluence (5 × 1013 ions/cm2), the electrical properties begin to improve. For the highest fluence (6 × 1015 ions/cm2), the sheet resistance is found to be 156 Ω/sq with an average visible transmission of 82%. The figure of merit value of our Al implanted ZnO film for an Al fluence of 5 × 1015 ions/cm2 is the highest till date, which may be prospective as a TCO layer. Detailed investigation on the evolution of the electrical and photoluminescence properties with an increase in the Al ion fluence reveals that zinc vacancy type defects are formed in large number which on healing produces further higher conductivity in the films. Image 1 • Sol-gel ZnO thin films were implanted with Al ions followed by annealing at 450 °C. • Film with 156 Ω/sq sheet resistance and >80% visible transmittance is produced. • Maximum FOM value of 9.57 × 10 −4 Ω −1 has been achieved. • Zinc vacancy plays a vital role in controlling the observed electrical properties. • The study is useful for understanding implantation effect and utilization of films as TCO. [ABSTRACT FROM AUTHOR]

Nanocrystalline La0.15Ca0.85MnO3 samples of various grain sizes ranging from ∼17 to 42 nm have been prepared by sol-gel technique. Phase purity and composition were verified by room temperature x-ray diffraction and SEM-EDAX analysis. The bulk La0.15Ca0.85MnO3 is known to order antiferromagnetically around 170 K and to undergo a simultaneous crystal structural transition. DC magnetization measurements on 17 nm size La0.15Ca0.85MnO3 show a peak at ∼130 K (TN) in zero-field-cooled (ZFC) state. Field-cooled magnetization bifurcates from ZFC data around 200 K hinting a weak ferromagnetic component near room temperature due to surface moments of the nanoparticle sample. Low temperature powder neutron diffraction experiments reveal that the incomplete structural transition from room temperature orthorhombic to low temperature orthorhombic-monoclinic state also occurs in the nanoparticle sample as in the bulk. Magnetization in the ordered state decreases as particle size increases, thus indicating the reduction of the competing ferromagnetic surface moments. [ABSTRACT FROM AUTHOR]

Kirkendall effect has played an important role in developing the understanding of atomic diffusion and mass transport in solids. In thin films and multilayers, in which the microstructure may be far from thermal equilibrium, behavior of a system can be very different from that of the bulk. Therefore, there is a great need to understand the peculiarities of Kirkendall shift occurring at nanometer or sub-nanometer length scale in such systems. In the present work, Kirkendall shift in thin films has been measured with sub-nanometer accuracy, by making use of x-ray planar waveguide structures. Using this technique, we report an apparently counterintuitive result of Kirkendall shift associated with self-diffusion in nanocrystalline iron. The cavity of the waveguide consists of two layers of iron having different microstructures, separated by a thin marker layer of Ag. Thermal annealing results in shift of the Ag marker towards the Fe layer having a coarser grain structure. The effect is established unambiguously by studying two samples with the order of the two Fe layers reversed, and a third sample with the two Fe layers having the same microstructure. The result can be understood in terms of the difference in the microstructure of the two Fe layers; difference in the grain size and hence different concentration of the grain boundaries in the two layers results in a net mass transfer from one region to the other. [Display omitted] [ABSTRACT FROM AUTHOR]

We report results of simultaneous x-ray reflectivity and grazing incidence x-ray fluorescence measurements in combination with x-ray standing-wave-assisted depth-resolved near-edge x-ray absorption measurements to reveal new insights on chemical speciation of W in a W-B4C multilayer structure. Interestingly, our results show the existence of various unusual electronic states for the W atoms especially those near to the surface and interface boundary of a thin film medium as compared to those of the bulk. These observations are found to be consistent with the results obtained using first-principles calculations. Unlike the conventional x-ray absorption measurements the present approach has an advantage that it permits the determination of the depth-resolved chemical nature of an element in the thin-layered materials at atomic length scale resolution. [ABSTRACT FROM AUTHOR]

HoCrO3, a member of the rare-earth chromate family, is known to exhibit an orthorhombic structure with Pbnm space group in bulk at room temperature. We have employed the pressure driven powder consolidation technique, spark plasma sintering, for synthesizing HoCrO3 powder-compact, which exhibits a superior quality with fewer defects over that synthesized by conventional solid-state sintering (resulting in a large reduction of charge carrier mediated extrinsic dielectric contribution). The powder compact shows magneto-dielectric coupling but does not exhibit a detectable ferroelectric phase in the range of 50 K to 300 K. Low temperature Raman spectra show structural distortions below 250 cm−1, indicating Ho ion displacements. Temperature evolution of the crystal structure using synchrotron x-ray diffraction reveals a probable structural phase transition below 240 K. Pyrocurrent measurement, together with synchrotron x-ray diffraction analysis, further points to a magneto-structural transition at 100 K. [ABSTRACT FROM AUTHOR]

Total reflection X-ray fluorescence (TXRF)-based X-ray absorption near-edge spectroscopy has been used to determine the oxidation state of uranium in mixed-valent U3O8 and U3O7 uranium oxides. The TXRF spectra of the compounds were measured using variable X-ray energies in the vicinity of the U L3 edge in the TXRF excitation mode at the microfocus beamline of the Indus-2 synchrotron facility. The TXRF-based X-ray absorption near-edge spectroscopy (TXRF-XANES) spectra were deduced from the emission spectra measured using the energies below and above the U L3 edge in the XANES region. The data processing using TXRF-XANES spectra of U(IV), U(V), and U(VI) standard compounds revealed that U present in U3O8 is a mixture of U(V) and U(VI), whereas U in U3O7 is mixture of U(IV) and U(VI). The results obtained in this study are similar to that reported in literature using the U M edge. The present study has demonstrated the possibility of application of TXRF for the oxidation state determination and elemental speciation of radioactive substances in a nondestructive manner with very small amount of sample requirement. [ABSTRACT FROM AUTHOR]

Dopant-profile independent electron transport has been observed through a combined study of temperature dependent electrical resistivity and magnetoresistance measurements on a series of Ti incorporated ZnO thin films with varying degree of static-disorder. These films were grown by atomic layer deposition through in-situ vertical stacking of multiple sub-monolayers of TiOx in ZnO. Upon decreasing ZnO spacer layer thickness, electron transport smoothly evolved from a good metallic to an incipient non-metallic regime due to the intricate interplay of screening of spatial potential fluctuations and strength of static-disorder in the films. Temperature dependent phase-coherence length as extracted from the magnetotransport measurement revealed insignificant role of inter sub-monolayer scattering as an additional channel for electron dephasing, indicating that films were homogeneously disordered three-dimensional electronic systems irrespective of their dopant-profiles. Results of this study are worthy enough for both fundamental physics perspective and efficient applications of multi-stacked ZnO/TiOx structures in the emerging field of transparent oxide electronics. [ABSTRACT FROM AUTHOR]

Connection between topological surface states (TSS) and large linear magnetoresistance (LMR) is established in tetradymite Bi 2 Te 3 through tuning of native defects. Thorough analysis of temperature dependent synchrotron X-ray diffraction data quantifies 0-D, 1-D and 2-D defect concentrations. Plausible variation of antisite defects is explained via carrier concentration data. Resistivity data divulge contribution of mixed bulk and surface states in the synthesized samples. High Fermi velocity (∼106 ms−1) and low Fermi energy (∼14 meV) of carriers are obtained. Lower defect concentration sample emerges with high magnetoresistance (MR) and higher mobility. Weak antilocalization (WAL) effect, signature of TSS, is revealed from MR. Large (80%), non-saturating LMR along with ultrahigh mobility (∼1 m2V−1s−1) in Bi 2 Te 3 supports the presence of TSS. Magnetoconductance data are fitted with Hikami-Larkin-Nagaoka equation, obtaining further insight on WAL effect. In addition, extracted parameters like disorder correlation length and coherence length explicate the role of defect density on LMR. [ABSTRACT FROM AUTHOR]

FeGa3 is a well known intermetallic semiconductor with a band gap, which is induced by d-p hybridization. In this work, we present the results of experimental and theoretical studies on the effect of Al substitution in FeGa3, obtained by X-ray diffraction (XRD) study, temperature dependent resistivity measurement, room temperature Mössbauer measurement, and density functional theory based electronic structure calculations. It is observed that up to x=0.178 in Fe(AlxGa1-x)3, which is the maximum range studied in this work, Al substitution reduces the lattice parameters a and c, preserving the parent tetragonal P42/mnm crystal structure of FeGa3. Rietveld refinement of the XRD data shows that Al atoms replace Ga atoms located at the 8j sites in FeGa3. A comparison of the trends of the lattice parameters and energy band gap obtained from the calculations and experimental measurements also confirms that Al atoms primarily replace the Ga atoms in the 8j site. The band gap of Fe(AlxGa1-x)3 for x=0.178 is reduced by ≈24% as compared to FeGa3. The system thus has a lot of promise for applications in band gap engineering in infra-red devices. [ABSTRACT FROM AUTHOR]

This article reports on the Ar+ ion irradiation induced modifications of Co/Alq 3 /Si-substrate bilayer thin film. Irradiation was carried out with 10 keV Ar+ ions at a fluence of 1 × 1016 ions/cm2. To study structural and magnetic modifications, x-ray reflectivity (XRR) and magneto-optical Kerr effect (MOKE) techniques, respectively have been utilized. XRR analysis reveals a significant reduction of electron density of the Co layer and enhancement of intermixing of Co and Alq 3 at the Co/Alq 3 interface after ion irradiation. MOKE measurements affirm that saturation magnetization reduces by a factor of about 3 due to irradiation without any detectable changes in the coercivity. XRR analysis and Monte Carlo simulation demonstrate the ion irradiation induced defects formation due to Ar implantation and enhancement of interface mixing between Co and Alq 3 is the main cause of the reduction in saturation magnetization. [ABSTRACT FROM AUTHOR]

• MSWI-FA is tested as either inert or reactive component in MKPC. • In both conditions, dissolution reactions involving Ca, Mg, S, Al, Si and Zn occur. • The precipitated secondary products are mostly amorphous phosphates. • The heavy metals leaching is below the Italian legal limits. • A 60% compressive strength increase is observed for the reactive formulation. In this study, the behaviour and reactivity of Municipal Solid Waste Incineration Fly Ash (MSWI-FA), introduced in the formulation of magnesium potassium phosphate cement (MKPC), was investigated by considering the waste either as fully inert or reactive. MSWI-FA induced structural and compositional modifications in MKPC as a consequence of dissolution/precipitation processes which involved many MSWI-FA elements (e.g., Ca, Mg, Al, Si, Zn) and led to the formation of mostly amorphous phosphate secondary products. The reaction path has been described in terms of the early fast dissolution of MSWI-FA, with precipitation of very low solubility phases, and subsequent late precipitation due to pH changes and water subtraction during MKPC gelification. The increase in amorphous content peaked to 50 wt.% and it has been related to the improved behaviour with respect to the leaching of heavy metals (reduced by 70-99%), pointing to this cement as an excellent matrix for their chemical stabilization. The obtained MKPC microstructure exhibited better mechanical performance, with an improvement of up to 60% in compressive strength. All in all, the results indicated that the incorporation in MKPC is a viable recycling opportunity for MSWI-FA, although, for an effective cement formulation, its reactivity must be taken into account. [ABSTRACT FROM AUTHOR]

The compositional profile and local atomic structure in a Co 40 Fe 40 B 20 thin film sandwiched between two W layers, have been probed combining time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray absorption fine structure spectroscopy techniques in standing wave geometry (SW-XAFS). The data analysis demonstrated inhomogeneities in the composition profile as well as in the local atomic structure around transition metals, along the film thickness. Boron concentration shows a gradual increase from the bottom to the surface of the film The quantitative analysis of the Fe and Co K edges SW-XAFS spectra reveals distinct differences in the local coordination geometry along the film thickness and between the two metals. Specifically, the local structure around Fe appeared to be more disordered on average compared to Co and the bond lengths exhibited significant variation as a function of depth, • SW-XAFS, XRR and TOF-SIMS were used to investigate the local atomic structure in W/Co 40 Fe 40 B 20 /W thin films. • SW-XAFS data show significant differences around Fe and Co, particularly for the Fe-B distribution. • The data analysis describes significant differences in the local coordination of Fe and Co in the film center with respect to the borders. [ABSTRACT FROM AUTHOR]

• 10 keV Ar+ ion implantation induced modifications has been explored in Co 20 Fe 60 B 20 /SmCo 5 bilayers. • Magnetic Coercivity has been increased by more than ten times after implantation. • X-ray reflectivity study revealed ion implantation causes significant microstructural modifications. • Enhancement of coercivity attributed to mixing of elements at the interface and Ar implantation induced defects creation. 10 keV Ar+ ion implantation induced modifications of nanoscale Co 20 Fe 60 B 20 /SmCo 5 /Si-substrate heterostructures have been investigated. Magneto-optic Kerr effect study reveals that the coercivity enhances by more than ten times after implantation. Implantation gives rise to an increase in surface roughness and densely packed grains as evident from the Atomic Force Microscopy study. X-ray reflectivity analysis manifests ion beam induced intermixing between elements of two layers at the interface and significant changes in the internal structure. Monte Carlo simulation study corroborates the x-ray reflectivity results. Enhancement of coercivity attributed to interface mixing and implantation induced defect creation in the films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Anomalous magnetic behavior is observed in Fe/Alq 3 bilayer. • Fe diffuses into Alq 3 to form 50 Å thick alloy layer at the interface. • Unexpected large effective magnetic dead layer is found at the interface. • Antiferromagnetic coupling between metallic Fe and alloyed Fe. Growth behavior and evolution of magnetism as a function of Fe thin film thickness onto organic semiconductor tris(8-hydroxyquinoline)-aluminum, (Alq 3) thin film was investigated in-situ using electrical resistance and magneto-optic Kerr effect (MOKE) measurements, respectively. The variation of electrical resistance with Fe film thickness reveals the Volmer-Weber growth of Fe on Alq 3 film. Reflection high energy electron diffraction (RHEED) pattern resembles polycrystalline BCC structure of Fe. Ex-situ x-ray reflectivity (XRR) measurement from the Fe/Alq 3 /Si sample reveals that Fe diffuses into Alq 3 to form an alloy layer of 50 Å thickness with Fe volume fraction of 0.4. In-situ MOKE study affirms anomalous magnetic behavior at the initial stage of Fe growth. Initially hysteresis loop appears and develops in a particular direction, and then vanishes at certain thickness. With further growth of Fe hysteresis loop appears again and grows in the opposite direction. The observed unusual changes in magnetic behavior as a function of Fe thickness may be explained in terms of the contribution from the magnetic Fe-Alq 3 alloy present in the intermix layer, the metallic Fe on top of Alq 3 layer, and their antiferromagnetic coupling. [ABSTRACT FROM AUTHOR]

Violacein is a naturally found pigment that is used by some gram negative bacteria to defend themselves from various gram positive bacteria. As a result, this molecule has caught attention for its potential biomedical applications and has already shown promising outcomes as an antiviral, an antibacterial, and an anti-tumor agent. Understanding the interaction of this molecule with a cellular membrane is an essential step to extend its use in the pharmaceutical paradigm. Here, the interaction of violacein with a lipid monolayer formed at the air–water interface is found to depend on electrostatic nature of lipids. In presence of violacein, the two dimensional (2D) pressure–area isotherms of lipids have exhibited changes in their phase transition pressure and in-plane elasticity. To gain insights into the out-of-plane structural organization of lipids in a membrane, X-ray reflectivity (XRR) study on a solid supported lipid monolayer on a hydrophilic substrate has been performed. It has revealed that the increase in membrane thickness is more pronounced in the zwitterionic and positively charged lipids compared to the negatively charged one. Further, the lipid molecules are observed to decrease their tilt angle made with the normal of lipid membrane along with an alteration in their in-plane ordering. This has been quantified by grazing incidence X-ray diffraction (GIXD) experiments on the multilayer membrane formed in an environment with controlled humidity. The structural reorganization of lipid molecules in presence of violacein can be utilized to provide a detailed mechanism of the interaction of this molecule with cellular membrane. [Display omitted] • Interaction of violacein with cellular membrane may control its activities. • Violacein can condense the in-plane organization of lipids in a cellular membrane. • Tilt angle of lipids in membranes changes due to the condensing effect of violacein. • Lipid membrane thickness increases as violacein penetrates into the membrane. [ABSTRACT FROM AUTHOR]