A5084803392- Magnetic properties of thin films
- Magnetic and transport properties of perovskites and related materials
- Quantum and electron transport phenomena
- Semiconductor materials and devices
- Electronic and Structural Properties of Oxides
- Atomic and Subatomic Physics Research
- Semiconductor materials and interfaces
- Rare-earth and actinide compounds
- Advanced NMR Techniques and Applications
- Physics of Superconductivity and Magnetism
- Solid-state spectroscopy and crystallography
- Semiconductor Quantum Structures and Devices
- Electron and X-Ray Spectroscopy Techniques
- Advanced Condensed Matter Physics
- Cardiovascular Syncope and Autonomic Disorders
- Classical Philosophy and Thought
- Advanced Memory and Neural Computing
- Theoretical and Computational Physics
- Perovskite Materials and Applications
- Magnetic Properties of Alloys
- Magnetic Field Sensors Techniques
- ZnO doping and properties
- Magneto-Optical Properties and Applications
- Electron Spin Resonance Studies
- Multiferroics and related materials
École Polytechnique Fédérale de Lausanne
2014-2018
Forschungszentrum Jülich
2011-2016
Indian Institute of Technology Delhi
2016
Jülich Aachen Research Alliance
2011-2013
Düsseldorf University Hospital
2013
Heinrich Heine University Düsseldorf
2013
University of Cologne
2012
We present a detailed study of the electronic structure and chemical state high-quality stoichiometric EuO O-rich ${\mathrm{Eu}}_{1}{\mathrm{O}}_{1+x}$ thin films grown directly on silicon without any buffer layer using hard x-ray photoemission spectroscopy (HAXPES). determine oxidation from consistent quantitative peak analysis $4f$ valence band $3d$ core-level spectra. The results prove that nearly ideal, stoichiometric, homogeneous can be silicon, with uniform depth distribution divalent...
Abstract Integrating epitaxial and ferromagnetic Europium Oxide (EuO) directly on silicon is a perfect route to enrich nanotechnology with spin filter functionality. To date, the inherent chemical reactivity between EuO Si has prevented heteroepitaxial integration without significant contaminations of interface Eu silicides oxides. We present solution this long-standing problem by applying two complementary passivation techniques for reactive EuO/Si interface: (i) an in situ hydrogen-Si...
Abstract We present an electronic structure study of a magnetic oxide/ semiconductor model system, EuO on silicon, which is dedicated for efficient spin injection and detection in silicon‐based spintronics devices. A combined analysis Eu core levels valence bands using hard X‐ray photoemission spectroscopy was performed to quantify the nearly ideal stoichiometry “spin filter” tunnel barriers directly absence silicon oxide at EuO/Si interface. These results provide evidence successful...
We present the chemical and structural optimization of ultrathin magnetic oxide EuO films on silicon. By applying a controlled in situ passivation Si(001) surface with SiOx monolayer regime, metallic silicide contaminations at interface can be effectively reduced down to sub-monolayer coverage, as was carefully quantified by interface-sensitive hard x-ray photoemission spectroscopy. Heteroepitaxial growth is sustained for this SiOx-passivation, bulk-near properties are observed 4 nm-thin...
Nuclear hyperpolarization in the liquid state by dynamic nuclear polarization (DNP) has been of great interest because its potential use NMR spectroscopy small samples biological and chemical compounds aqueous media. Liquid DNP generally requires microwave resonators order to generate an alternating magnetic field strong enough saturate electron spins solution. As a consequence, sample size is limited dimensions wavelength, this restricts volume less than 100 nL for at 9 T (∼260 GHz). We...
Detection of sub-THz spin cycloid resonances (SCRs) stoichiometric BiFeO3 (BFO) was demonstrated using a vector network analyzer. Continuous wave absorption spectroscopy is possible, thanks to heterodyning and electronic sweep control frequency extenders for frequencies from 480 760 GHz. High resolution reveals SCR peaks with precision in the ppm regime. Three distinct features BFO were observed identified as Ψ1 Φ2 modes, which are out-of-plane in-plane modes cycloid, respectively. A...
The origin of the Curie temperature enhancement EuO upon Gd doping is studied by using soft x-ray absorption spectroscopy on epitaxial pure and Gd-doped thin films. Temperature- doping-dependent changes in oxygen K edge spectra provide information about correlation magnetism lattice. Band-structure calculations reveal that these spectral as well increase to 125 for cannot be explained electron alone. compression crystal lattice due incorporation smaller Gd${}^{3+}$ ions plays also an important role.
We demonstrate the high-quality heteroepitaxy of ultrathin EuO films with bulklike ferromagnetism directly on MgO (001), an important step towards combining spin-filter tunnel effect in magnetic insulators and symmetry-filter tunneling through single-crystalline barriers. Despite a large compressive lattice mismatch, grows fully relaxed (001) adopts its bulk parameter from first monolayer on. This initial heteroepitaxial growth mode is discussed terms different electrostatic atomic...
260-GHz radiation is used for a quasi-optical electron spin resonance (ESR) spectrometer which features both field and frequency modulation. Free space propagation to implement Martin-Puplett interferometry with isolation, mirror beam focusing, electronic polarization control. Computer-aided design pathway simulation lead the of compact interferometer, featuring lateral dimensions less than foot high mechanical stability, all components rated power levels several Watts suitable gyrotron...
We demonstrate opto-spintronics using Fe-doped Indium Phosphide (InP). The method is based on optical orientation of InP conduction electron spins which are electrically detected in planar InP/oxide/Ni tunnel spin filters. separate the excitation from electrical detection, avoiding thus additional interactions photons with ferromagnet. Interface engineering provides a surface iron accumulation and semiconducting Fe:In2O3 oxide barrier. filtering effect switches to positive or negative...
We report an in situ thermochemical treatment that significantly increases the macroscopic electrical conductivity of insulating yttria-stabilized zirconia (YSZ) (001) single-crystalline substrates. demonstrate high-quality surface crystalline structure resulting “conductive” cYSZ by low- and high-energy electron diffraction. Soft- hard X-ray photoemission spectroscopy measurements reveal a sizable reduction Zr cations to metallic state their homogeneous distribution within cYSZ. discuss...
The existence of a heat-driven spin torque is demonstrated using Co/Cu/Co valves embedded in metallic nanowires. Heat currents flowing one direction or its opposite were obtained by heating optically end the other associated with current pushes magnetization out equilibrium, resulting change magnetoresistance, which detected charge small enough not to cause induced fields any significance. giant magnetoresistance response this peaks magnetic susceptibility, whereas spurious signal coming...
The electrical detection of surface spin polarization in Indium Phosphide (InP) is demonstrated. Using a planar four-terminal architecture on top semi-insulating Fe:InP (001) wafers, optical orientation separated from detection. Spin filter tunnel contacts consisting InP/oxide/Co reveal significant asymmetries the differential resistance upon helicity change pumping. iron-rich oxide provides main selection mechanism. A reproducible helicity-dependent asymmetry as high 18% could be observed...
We have investigated a method for substituting oxygen with nitrogen in EuO thin films, which is based on molecular beam epitaxy distillation NO gas as the oxidizer. By varying pressure, we produce crystalline, epitaxial EuO1-xNx films good control over films’ concentration. In situ x-ray photoemission spectroscopy reveals that substitution connected to formation Eu3+4f6 and corresponding decrease number of Eu2+4f7, indicating being incorporated its 3− oxidation state. While small amounts...
Dynamic nuclear polarization (DNP) enhances magnetic resonance (NMR) signals by transferring electron spin to nuclei. As DNP requires microwave fields B1 strong enough saturate spins, resonators are generally used achieve a sufficient B1, at the expense of restricting sample size. Higher improve NMR sensitivity and resolution. However, 9 T for example can only hold nano-liters (nL). Larger volumes possible avoiding resonators, but higher power needed reach is likely evaporate sample. Here,...