A5049837152- Magnetic properties of thin films
- Magnetic Properties and Applications
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Electronic and Structural Properties of Oxides
- Magnetic Properties of Alloys
- Electron and X-Ray Spectroscopy Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Iron oxide chemistry and applications
- Characterization and Applications of Magnetic Nanoparticles
- Magnetic Properties and Synthesis of Ferrites
- Rare-earth and actinide compounds
- Theoretical and Computational Physics
- Surface and Thin Film Phenomena
- Advancements in Solid Oxide Fuel Cells
- Advanced Chemical Physics Studies
- ZnO doping and properties
- Advanced Electron Microscopy Techniques and Applications
- Semiconductor materials and devices
- X-ray Diffraction in Crystallography
- Multiferroics and related materials
- Iron-based superconductors research
- Heusler alloys: electronic and magnetic properties
- Quantum and electron transport phenomena
Montana State University
2012-2023
Lawrence Berkeley National Laboratory
2008-2018
Massachusetts Institute of Technology
2012
National Institute of Standards and Technology
2012
Montana Technological University
2012
National Chemical Laboratory
2008
University of California, Davis
2008
University of Maryland, College Park
2008
United States Naval Research Laboratory
1992-2001
FZI Research Center for Information Technology
1996-2000
High precision, $L$${}_{2,3}$-edge photoabsorption and magnetic circular dichroism spectra of iron cobalt were measured in transmission with situ grown thin films, eliminating experimental artifacts encountered by the indirect methods used all previous measurements. The moments determined from integrals these are found to be excellent agreement (within 3%) for orbital spin moment ratios, good 7%) individual moments, those obtained Einstein--de Haas gyromagnetic ratio measurements,...
Saturation effects are determined in x-ray magnetic circular dichroism spectra, acquired by electron yield techniques. It is shown that sum-rule extraction of the number d holes, orbital moment, and spin moment affected for Fe, Co, Ni. In particular, errors extracted values due to saturation can be excess 100% even wrong sign films as thin 50 \AA{}. They significant film thicknesses a few monolayers. Errors derived holes considerably smaller but may order 10--20 %. Correction factors given...
The Landau-Lifshitz equation reliably describes magnetization dynamics using a phenomenological treatment of damping. This Letter presents first-principles calculations the damping parameters for Fe, Co, and Ni that quantitatively agree with existing ferromagnetic resonance measurements. agreement establishes dominant mechanism these systems takes significant step toward predicting tailoring constants new materials.
We have investigated the electronic structure associated with ferromagnetic transition of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ and ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Pb}}_{x}{\mathrm{MnO}}_{3}$ using high resolution photoemission, Mn 2p resonant O 1s x-ray absorption spectroscopies. The data clearly show that band gap collapses below Curie temperature $({T}_{C})$ density states at Fermi level increases cooling, providing a conclusive microscopic...
A large exchange splitting of the conduction band in ultrathin films ferromagnetic semiconductor EuO was determined quantitatively, by using as a tunnel barrier and fitting current-voltage characteristics temperature dependence to tunneling theory. This leads different heights for spin-up spin-down electrons is enough produce near-fully spin-polarized current. Moreover, magnetic properties these (<6 nm) show reduction Curie with decreasing thickness, agreement theoretical calculation [R....
Dichroic interference effects were observed in circularly polarized soft-x-ray reflectivity at the Co ${\mathit{L}}_{2,3}$ edges of a magnetic multilayer. The data show maximum asymmetry ratio 80%, greater than degree circular polarization incident light, changeover dichroic characteristics with increasing grazing angle, and an inverted pattern angular dependence ratio. These observations are explained successfully by classical electromagnetic model calculation which includes complete state...
Using polarization-dependent $\mathrm{O}1s$ and $\mathrm{Cu}2p$ near-edge x-ray absorption spectroscopy on detwinned ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}$ single crystals, the unoccupied electronic structure of ${\mathrm{CuO}}_{2}$ planes ${\mathrm{CuO}}_{3}$ chains has been studied. Unlike conventional picture where superconductivity is related predominantly to number planar holes, we find clear evidence for a...
We report element-specific magnetic hysteresis measurements on heteromagnetic materials. Dramatically different Fe and Co curves of Fe/Cu/Co trilayers were obtained by recording the circular dichroism at their respective ${\mathit{L}}_{3}$ white lines as a function applied field. The data resolve complicated curves, observed conventional magnetometry, determine individual moments for layers. Fine features, imperceptible in also observed, demonstrating new powerful means studying multilayer systems.
The unoccupied electronic structure for the ${\mathrm{Sr}}_{14}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ family of two-leg ladder compounds was investigated different partial substitutions ${\mathrm{Sr}}^{2+}$ by ${\mathrm{Ca}}^{2+},$ leaving nominal hole count constant, and ${\mathrm{Y}}^{3+}$ or ${\mathrm{La}}^{3+},$ reducing from its full value 6 per formula unit. Using polarization-dependent x-ray absorption spectroscopy on single crystals, states both chain sites could be studied. While...
This work focuses on the synthetic control of magnetic properties mixed oxide nanoparticles general formula Fe3-xCoxO4 (x ≤ 0.33) in protein cage ferritin. In this biomimetic approach, variations chemical synthesis result formation single-phase alloys or intimately binary phase Fe/Co oxides, modifying structure and behavior these particles, as characterized by static dynamic magnetization measurements X-ray absorption spectroscopy.
Substituting Y in orthorhombic (Y,R)${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ by any rare-earth element R has generally little effect on the superconducting properties. For R=Pr, however, superconductivity is completely suppressed. To understand this we have studied unoccupied electronic structure of ${\mathrm{Pr}}_{\mathrm{x}}$${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{y}}$...
From magnetic circular dichroism measurements of the Heusler alloy NiMnSb, in combination with other techniques, we show that a dramatic increase Mn and Ni moments occurs below ``crossover'' transition temperature about 80--100 K. This phase is well Curie NiMnSb (\ensuremath{\sim}730 K). While spin polarization near Fermi level, from spin-polarized inverse photoemission, remains very high for ${k}_{\ensuremath{\parallel}}=0,$ it unlikely half-metallic ferromagnet room temperature.
Temperature-dependent magnetic measurements are reported for 4.34 nm antiferromagnetic Co3O4 nanoparticles mineralized in the Listeria innocua Dps protein cage. ac show a superparamagnetic blocking temperature of roughly 5.4 K and give an extracted anisotropy energy density (7.6±0.4)×104J∕m3. The Néel nanoparticles, determined with dc magnetometry, was to be 15±2K.
We provide a simple explanation, based on an effective field, for the precession damping rate due to spin-orbit interaction. Previous field treatments of include only variations state energies with respect magnetization direction, effect referred as breathing Fermi surface. Treating interaction rotating spins orbits perturbation, we also changes in populations field. In order investigate quantitative differences between rates iron, cobalt, and nickel, compute dependence density states...
Abstract This work demonstrates the critical role of orbital hybridizations in FeO 6 octahedral distortion, composition‐driven phase transition, and bonding covalency multiferroic (Bi 1− x Sm )FeO 3 ( = 0.10‐0.20) ceramics vicinity morphotropic boundary (MPB). Sequential transitions from polar rhombohedral R c to antipolar orthorhombic Pbam then Pnma phases were revealed as system crosses MPB with increasing Sm. A coexistence ferroelectric (FE) antiferroelectric (AFE) PbZrO ‐like symmetries...
The angular dependence of the magnetic linear dichroism in Fe and Co $3p$ photoemission is investigated. has same symmetry behavior as free atom, vanishes when integrated over all angles. However, shows pronounced deviations from $\mathrm{sin}2\ensuremath{\theta}$ atom. qualitative features can be understood terms a photoelectron diffraction picture, taking into account details final state wave functions with respect to momentum quantum numbers.
Energy and helicity-dependent absolute photoabsorption cross sections at the Fe ${L}_{2,3}$ edge, measured in transmission from a supported ultrathin film, are presented. These semiempirical total-electron-yield (TEY) equations used to show that effects of saturation/self-absorption TEY spectra, as reflected quantitative evaluation magnetic moments, can be quite severe. conclusions confirmed by directly comparing data obtained simultaneously transmission.
Soft X-ray magnetic circular dichroism is the difference in total absorption cross-section of positive and negative helicity circularly-polarized soft X-rays at magnetically interesting L2 L3 edges 3d transition metals or M4 M5 rare earths. The can be measured using a variety techniques including transmission, partial electron yield, fluorescence sample current, reflection. different measurement schemes represent probing depths, allowing depth dependent studies, are complementary to each...
The epitaxial growth of fcc iron films on the (001) face diamond has been achieved. were studied by reflection high-energy electron diffraction and angle-resolved Auger diffraction. studies show that 4–5 atomic layers Fe C(100) form a continuous film. as deposited at room temperature are disordered, after high-temperature anneal have structure temperature.