X-ray Magnetic Circular Dichroism (x-ray + magnetic_circular_dichroism)

Distribution by Scientific Domains


Selected Abstracts


Magnetic Materials: X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for Nanodevices (Adv. Mater.

ADVANCED MATERIALS, Issue 2 2009
2/2009)
The surface sensitivity of X-ray magnetic circular dichroism in extreme conditions has been exploited to investigate the first layers of bulk single-molecule magnets (SMMs), as reported by Roberta Sessoli and co-workers on p. 167. Striking differences have emerged between two classes of SMM having different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices. [source]


X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for Nanodevices

ADVANCED MATERIALS, Issue 2 2009
Matteo Mannini
The surface sensitivity of X-ray Magnetic Circular Dichroism in extreme conditions is exploited to investigate the first layers of bulk single-molecule magnets (SMM). Striking differences emerge between two classes of SMM with different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices [source]


Magnetic and Structural Investigation of ZnSe Semiconductor Nanoparticles Doped With Isolated and Core-Concentrated Mn2+ Ions

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2009
Christina Graf
X-Ray magnetic circular dichroism (XMCD) experiments on diluted magnetic semiconductor nanocrystals (2,7,nm) are reported in order to study their local electronic structure and magnetic properties. ZnSe nanoparticles containing either single manganese ions (Mn2+) distributed in the lattice of the entire particle or a MnSe core in the center are prepared using high temperature approaches. The Mn2+ concentration is varied between less than one to several tens of manganese ions per nanocrystal. For all samples it is shown that the Mn2+ is exclusively present in the bulk of ZnSe nanoparticles with no evidence for oxidation to higher Mn-oxidation states. The magnetic ions are highly polarized inside the nanocrystals reaching about 80% of the theoretical value of a pure d5 state under identical conditions for the case of isolated manganese ions. Nanocrystals with a MnSe core ZnSe shell structure reach <50% of this value. Thus, their polarization is significantly more hindered, which is due to the significantly enhanced Mn,Mn interactions and a more distorted crystalline lattice. In contrast, no coupling between the manganese centers is observed in the nanoparticles doped samples with low concentrations of Mn2+, indicating that these ions are isolated in the bulk of the nanoparticles. [source]


X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for Nanodevices

ADVANCED MATERIALS, Issue 2 2009
Matteo Mannini
The surface sensitivity of X-ray Magnetic Circular Dichroism in extreme conditions is exploited to investigate the first layers of bulk single-molecule magnets (SMM). Striking differences emerge between two classes of SMM with different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices [source]


Application of Synchrotron Radiation Techniques for Model Validation of Advanced Structural Materials,

ADVANCED ENGINEERING MATERIALS, Issue 6 2009
Annick Froideval
Abstract Synchrotron radiation techniques represent powerful tools to characterize materials down to the nanometer level. This paper presents a survey of the state-of-the-art synchrotron-based techniques which are particularly well-suited for investigating materials properties. Complementary X-ray absorption techniques such as extended X-ray absorption fine structure (EXAFS), X-ray magnetic circular dichroism (XMCD), photoemission electron microscopy (PEEM) are used to address the individual local atomic structure and magnetic moments in Fe,Cr model systems. The formation of atomic clusters/precipitates in such systems is also investigated by means of scanning transmission X-ray microscopy (STXM). Such advanced analytical techniques can not only offer valuable structural and magnetic information on such systems, they can also serve for validating computational calculations performed at different time and length scales which can help improve materials lifetime predictions. [source]


The Quest for Nanoscale Magnets: The example of [Mn12] Single Molecule Magnets

ADVANCED MATERIALS, Issue 43 2009
Guillaume Rogez
Abstract Recent advances on the organization and characterization of [Mn12] single molecule magnets (SMMs) on a surface or in 3D are reviewed. By using nonconventional techniques such as X-ray magnetic circular dichroism (XMCD) and scanning tunneling microscopy (STM), it is shown that [Mn12]-based SMMs deposited on a surface lose their SMM behavior, even though the molecules seem to be structurally undamaged. A new approach is reported to get high-density information-storage devices, based on the 3D assembling of SMMs in a liquid crystalline phase. The 3D nanostructure exhibits the anisotropic character of the SMMs, thus opening the way to address micrometric volumes by two photon absorption using the pump-probe technique. We present recent developments such as µ-SQUID, magneto-optical Kerr effect (MOKE), or magneto-optical circular dichroism (MOCD), which enable the characterization of SMM nanostructures with exceptional sensitivity. Further, the spin-polarized version of the STM under ultrahigh vacuum is shown to be the key tool for addressing not only single molecule magnets, but also magnetic nano-objects. [source]


Magnetic Materials: X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for Nanodevices (Adv. Mater.

ADVANCED MATERIALS, Issue 2 2009
2/2009)
The surface sensitivity of X-ray magnetic circular dichroism in extreme conditions has been exploited to investigate the first layers of bulk single-molecule magnets (SMMs), as reported by Roberta Sessoli and co-workers on p. 167. Striking differences have emerged between two classes of SMM having different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices. [source]


X-ray magnetic circular dichroism measurements using an X-ray phase retarder on the BM25 A-SpLine beamline at the ESRF

JOURNAL OF SYNCHROTRON RADIATION, Issue 3 2010
Roberto Boada
Circularly polarized X-rays produced by a diamond X-ray phase retarder of thickness 0.5,mm in the Laue transmission configuration have been used for recording X-ray magnetic circular dichroism (XMCD) on the bending-magnet beamline BM25A (SpLine) at the ESRF. Field reversal and helicity reversal techniques have been used to carry out the measurements. The performance of the experimental set-up has been demonstrated by recording XMCD in the energy range from 7 to 11,keV. [source]


Origin of the X-ray magnetic circular dichroism at the L -edges of the rare-earths in RxR1,x,Al2 systems

JOURNAL OF SYNCHROTRON RADIATION, Issue 3 2009
Jesús Chaboy
An X-ray magnetic circular dichroism (XMCD) study performed at the rare-earth L2,3 -edges in the RxR1,x,Al2 compounds is presented. It is shown that both R and R, atoms contribute to the XMCD recorded at the L -edges of the selected rare-earth, either R or R,. The amplitude of the XMCD signal is not directly correlated to the magnetization or to the value of the individual (R, R,) magnetic moments, but it is related to the molecular field acting on the rare-earth tuned in the photoabsorption process. This result closes a longstanding study of the origin of the XMCD at the L -edge of the rare-earths in multi-component systems, allowing a full understanding of the exact nature of these signals. [source]


XAS and XMCD under high magnetic field and low temperature on the energy-dispersive beamline of the ESRF

JOURNAL OF SYNCHROTRON RADIATION, Issue 5 2007
O. Mathon
The present paper demonstrates the feasibility of X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) under high magnetic fields up to 26,T and low temperatures down to 5,K on the ID24 energy-dispersive XAS beamline of the ESRF. The pulsed magnetic field set-up, entirely developed at the ESRF, is described as well as the beamline set-up, the synchronization and the measurement procedure. It allows field strengths up to 30,T. Finally, as an example, we report a recent XMCD study at the Re L2 and L3 absorption edges of the double perovskite Sr2CrReO6. [source]


Magnetic X-ray absorption fine structure for Ni,Mn alloys

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2003
T. Miyanaga
Magnetic X-ray absorption fine-structure (XAFS) spectra have been measured for Ni,Mn alloys. The magnetic XAFS in the near-edge region (X-ray absorption near-edge structure, XANES) and X-ray magnetic circular dichroism (XMCD) of the Mn and Ni K -edge for Ni1,xMnx (x = 0.25, 0.24 and 0.20) show that (i) the local magnetic structure around the Mn atom is quite different from that around the Ni atom, and (ii) the peak intensity in the magnetic XANES of the Mn K -edge depends on the magnetization of the sample in contrast to the Ni K -edge. The Mn K -edge magnetic EXAFS (extended XAFS) for Ni0.76Mn0.24 is also measured. The second and fourth peaks in the Fourier transform are observed to be enhanced in comparison with the non-magnetic EXAFS, indicating that the second- and fourth-shell Ni atoms are replaced by Mn atoms due to heat treatment (atomic ordering). Semi-relativistic theoretical calculation explains the observed magnetic EXAFS. [source]


X-ray magnetic circular dichroism imaging with hard X-rays

JOURNAL OF SYNCHROTRON RADIATION, Issue 3 2001
K. Sato
X-ray polarization-contrast images resulting from X-ray magnetic circular dichroism (XMCD) in the hard X-ray region have been successfully recorded for the first time. The apparatus used consisted of an X-ray polarizer, double X-ray phase retarders, and a high-spatial-resolution X-ray charge-coupled-device detector. The sample used was a hexagonal-close-packed cobalt polycrystal foil having a thickness of about 4,µm. The X-ray polarization-contrast image resulting from XMCD was observed at a photon energy of 10,eV above the cobalt K -absorption edge (7709,eV). The observed contrast in the image was reversed by inversion of the magnetic field. Furthermore, the contrast was reversed again at a photon energy of 32,eV above the cobalt K -absorption edge. [source]


Anisotropic features in XMCD spectra

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001
Shin-ichi Nagamatsu
The angular dependent K -edge X-ray magnetic circular dichroism (XMCD) spectra based on the semi-relativistic full multiple scattering theory are discussed, where 2-spinor formalism is used to describe spin-orbit coupling. So far most of theoretical approaches have been limited to the simplest case where the circularly polarized X-ray propagation coincides with the direction of the magnetic field. Here we discuss more general cases, using the above theoretical approaches. We separately discuss atomic, single and full multiple scattering XMCD spectra; in particular anisotropic features of them are studied in detail. [source]


Electronic states in Cu2MnX (X = Al, In and Sn) Heusler alloy studied by XMCD and multiple scattering calculations

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001
Shigeaki Uemura
X-ray magnetic circular dichroism (XMCD) has been measured at Mn and Cu K-edge in Cu2MnX (X = Al, In, and Sn) Heusler alloy. The Mn K -edge spectrum shows a dispersion-type profile and the Cu K -edge resembles the Mn spectrum, which suggests that polarization of the p unoccupied bands originates commonly in Mn 3d states. To reproduce the observed spectrum by full multiple scattering calculations, Madelung potential has been taken into account. Charge redistribution is an important factor for the electronic structure in Cu2MnX Heusler alloy. [source]


Experimental and theoretical study of the magnetic properties and XMCD spectra of Ru clusters deposited on Fe/Cu(001)

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2010
J. Minár
Abstract We present results of an experimental study of magnetic properties of small Ru clusters deposited on a thin Fe film grown on Cu(001) surface. X-ray magnetic circular dichroism (XMCD) measurements show finite spin and orbital moments of Ru dimers and trimers, however a magnetic moment for a Ru monomer has been not observed. A corresponding theoretical study based on the fully relativistic multiple scattering KKR method is presented. Detailed theoretical analysis has been performed to explain the experimental findings. In particular a direct comparison of the calculated XMCD with the experiments suggests diffusion into the surface as a possible reason for the apparent quenching of the spin magnetic moment for Ru monomers. [source]