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Spinel-type compounds of Fe–Ni–Sb–O system were synthesized as polycrystalline powders. The crystal and magnetic properties were investigated using X-ray and neutron powder diffraction, Mossbauer and X-ray absorption spectroscopy and magnetization measurements. The samples crystallize in the cubic system, space group Fd – 3 m. The distribution of cations between octahedral and tetrahedral sites was refined from the diffraction data sets using constraints imposed by the magnetic, Mossbauer and EDS results and the ionic radii. The cation distribution and the temperature dependence of the lattice parameter (a) and the oxygen positional parameter (u) were obtained. A chemical formula close to Fe0.8Ni1.8Sb0.4O4 was determined, with Sb5+ cations occupying octahedral sites, and Fe3+ and Ni2+ occupying both tetrahedral and octahedral sites. Fe3+ mainly (85/15 ratio) occupy tetrahedral sites, and conversely Ni2+ mainly reside on octahedral ones. The magnetic unit cell is the same as the crystallographic one, having identical symmetry relations. The results indicate that the compounds have a collinear ferrimagnetic structure with antiferromagnetic coupling between the tetrahedral (A) and octahedral (B) sites. Uniquely, the temperature dependence of the net magnetization of this rare earth free ferrimagnet exhibits a compensation point.

The effect of the presence of CeO2 in the source material on the properties of SiC crystals grown by Physical Vapor Transport (PVT) method is investigated. The doping efficiency and, indirectly, the presence of the cerium vapour in the growth atmosphere were examined by study of structural, electrical and optical properties of the crystals. X-ray photoelectron spectroscopy shows that Ce2O3 and CeO2 coexist on the SiC post-growth surfaces. A detectable Ce incorporation is observed only in the last grown part of the crystal.

A method for producing self-organised arrays of nanometric metallic dots is reported. It consists on developing first the nanodot pattern by ion erosion on a semiconductor cover film and transferri ...

The article presents, using Bi doped ZnO, an example of a heavy ion doped oxide semiconductor, highlighting a novel p-symmetry interaction of the electronic states to stabilize ferromagnetism. The study includes both ab initio theory and experiments, which yield clear evidence for above room temperature ferromagnetism. ZnBixO1−x thin films are grown using the pulsed laser deposition technique. The room temperature ferromagnetism finds its origin in the holes introduced by the Bi doping and the p-p coupling between Bi and the host atoms. A sizeable magnetic moment is measured by means of x-ray magnetic circular dichroism at the O K-edge, probing directly the spin polarization of the O(2p) states. This result is in agreement with the theoretical predictions and inductive magnetometry measurements. Ab initio calculations of the electronic and magnetic structure of ZnBixO1−x at various doping levels allow to trace the origin of the ferromagnetic character of this material. It appears, that the spin-orbit energy of the heavy ion Bi stabilizes the ferromagnetic phase. Thus, ZnBixO1−x doped with a heavy non-ferromagnetic element, such as Bi, is a credible example of a candidate material for a new class of compounds for spintronics applications, based on the spin polarization of the p states.

The temperature-driven spin-reorientation transition (SRT) has been investigated in a layer of 2.1 nm Co in Au/Co/Au. We studied the evolution and stability of the in-plane magnetization components in the temperature range from 300 to 90 K by means of polarized neutron reflectometry (PNR) and Co L-edge X-ray magnetic circular dichroism (XMCD) measurements. The PNR measurement provides evidence for the occurrence of a SRT in this temperature range. XMCD can be used as a vector magnetometer that yields both the in- and out-of-plane magnetization components per Co atom. Combining the results of both techniques (PNR and XMCD) allows separating the orbital and spin magnetic moments using magneto-optical sum rules. We observed that already above the SRT the in-plane orbital moment component changes significantly stronger than the spin component.

The presence of oscillatory structures in the atomic x-ray absorption background is reported for the first time for surface-EXAFS of cN/Cu(100) and N/Cu(110). Systematic analysis of this feature (AXAFS) and comparison to theory yields new information on the electronic structure of the adsorbate - substrate surface bond. Also, angle and temperature dependent analysis of the AXAFS peak provides qualitative information about interstitial charge density distribution.

A series of (Zn,Co)O layers with Co contents x up to 40% grown by atomic layer deposition have been investigated. All structures deposited at 160 degrees C show magnetic properties specific to II-V ...

We have performed x-ray absorption spectroscopy at the Fe, Ni, and Co L 2,3 edges of in situ grown thin magnetic films. We compare electron yield measurements performed at SSRL and BESSY-I. Differences in the L 2,3 white line intensities are found for all three elements, comparing data from the two facilities. We propose a correlation between spectral intensities and the degree of spatial coherence of the exciting radiation. The electron yield saturation effects are stronger for light with a higher degree of spatial coherence. Therefore the observed, coherence related, intensity variations are due to an increase in the absorption coefficient, and not to secondary channel related effects.

Ultra thin films of Fe deposited on the (100) surface of a Cu single crystal exhibit a net perpendicular magnetic anisotropy. The addition of very low coverages of Co results in the easy magnetic direction reorienting into the film plane. This behavior is in contrast to the addition of similar amounts of Fe, whereupon the ferromagnetic response vanishes. This result is discussed in terms of the anisotropy energies derived from the spectroscopic data.

We report on the characterization of the new I1011 beamline at the MAX-II storage ring, in the MAX-lab synchrotron radiation laboratory and give examples of first results. This beamline is using an Elliptically Polarizing Undulator source, producing soft x-rays of a variable polarization state. It delivers high flux and high brightness circularly polarized x-rays in the energy range 0.2 to 1.7 keV, covering the L-edges of the late 3d elements. The new beamline will operate with an octupole magnet endstation. It is specially engineered to solve the problem of the limited optical access typically associated with magnetic fields and synchrotron radiation endstations. Eight water-cooled magnets allow the application of the magnetic field of up to 1 T in any direction. X-ray absorption spectroscopy, X-ray resonant reflectivity and the corresponding magnetic variants, i.e., XMCD, XMLD and XRMS experiments are possible also under an applied magnetic field. The high flux allows working with dilute magnetic systems such as ultra-thin films and nano structures.

The structural and magnetic properties of MnSb layers grown on two differently oriented GaAs substrates are reported. The MnSb compounds grow nonhomogenously both on GaAs(111)B and on GaAs(100) substrates. In x-ray diffraction studies the formation of two epitaxial domains is observed depending on the crystallographic orientation of the substrate. The observed diffusion of Ga atoms from the substrate to the layers results in the formation of an additional Mn-rich cubic phase of GaMnSb. In the case of the (100) oriented substrate, the diffusion of Mn into the substrate was additionally found. Traces of other phases were also noticed. The complex morphology of the layers is found to influence their magnetic properties. Magnetic force microscopy images revealed an inhomogenous distribution of the magnetic force gradient on the surface and the formation of magnetic domains in the samples. X-ray absorption studies of the chemical bonding and local atomic structure around Mn atoms confirmed high structural and chemical disorder in the samples. The chemical bonding of the dominating fraction of Mn atoms is found, however, similar to that in the reference MnSb powder. The x-ray magnetic circular dichroism measurements reveal an enhanced orbital moment and a reduced spin moment, which is most likely caused by the presence of different phases and a Mn-rich surface in the investigated samples.

We have used the x-ray magnetic circular dichroism technique to characterize ultrathin Co films deposited on flat and vicinal Cu(111) single crystal surfaces. All films were prepared and characterized in situ, in ultrahigh vacuum. Similar to other investigators we report a 40% increase of the ratio m(l)/m(s) (orbital to spin moment) of ultrathin Co on both flat and vicinal Cu(111). In addition, an apparently correlated enhancement of both the orbital and spin moments is observed for Co on vicinal Cu(111). This finding is in contrast to what has earlier been reported for a similar system, Co on vicinal Cu(100). (C) 2002 American Institute of Physics.

The near edge X-ray absorption fine structure (NEXAFS) at the C K-edge of C2H2, C2H4, C2H6 on Cu(100) and Ag(100) surfaces is studied. The oriented character of the molecules on the surface combined to the dipole selection rules for photon absorption allows an experimental assignment of the nature of the various final states. A careful fitting of the NEXAFS spectra reveals final states of C–H character and shake-up satellites of the C(1 s) to π* (C–C) transition. The asymmetric line shape of the C(1 s) to σ* (C–C) transition is described in a scattering model of the photoelectron from the molecular potential.

We present torque experiments on CuMn alloys which illustrate the triad anisotropy of spin glasses. We also discuss the mechanisms giving rise to the triad anisotropy and we show how the anisotropy can be ‘‘shaped’’ at will.