A5075674719- Magnetic properties of thin films
- Advanced Condensed Matter Physics
- Iron oxide chemistry and applications
- Physics of Superconductivity and Magnetism
- Multiferroics and related materials
- Magnetic Properties and Synthesis of Ferrites
- Characterization and Applications of Magnetic Nanoparticles
- Magnetic and transport properties of perovskites and related materials
- Magnetic Properties and Applications
- Chemical Thermodynamics and Molecular Structure
- Solid-state spectroscopy and crystallography
- Plasmonic and Surface Plasmon Research
- ZnO doping and properties
- Electron and X-Ray Spectroscopy Techniques
- Electronic and Structural Properties of Oxides
- Ferroelectric and Piezoelectric Materials
- Crystallography and molecular interactions
- Topological Materials and Phenomena
- Anodic Oxide Films and Nanostructures
- Graphene research and applications
- Thermodynamic properties of mixtures
- Photonic Crystals and Applications
- Gold and Silver Nanoparticles Synthesis and Applications
- Diamond and Carbon-based Materials Research
- Magneto-Optical Properties and Applications
Institut de Nanociència i Nanotecnologia de la Universitat de Barcelona
2011-2024
Universitat de Barcelona
2015-2024
FC Barcelona
2016-2021
Paul Scherrer Institute
2006-2012
Trinity College
2012
Swiss Light Source
2007-2011
Uppsala University
2003-2009
University of Konstanz
2008
University of the Basque Country
1999-2005
We report the near-edge x-ray absorption fine-structure (NEXAFS) spectrum of a single layer graphite (graphene) obtained by micromechanical cleavage highly ordered pyrolytic on SiO2 substrate. utilized photoemission electron microscope to separately study single-, double-, and few-layers graphene samples. In single-layer we observe splitting pi resonance clear signature predicted interlayer state. The NEXAFS data illustrate rapid evolution electronic structure with increased number layers.
Measurements of the $^{23}\mathrm{Na}$ nuclear-relaxation time ${T}_{1}$ are reported for two types Na $\ensuremath{\beta}$-alumina specimen, i.e., flux-grown crystals from our laboratory and melt-grown Union Carbide Corp. A phenomenological calculation due to activated hopping motion, taking account local variations in energy-barrier heights, is presented. This theory used interpret own data, plus data on literature specimens prepared by a third method, terms barrier-height distributions....
Arrays of dipolar coupled ferromagnetic islands arranged in specific geometries provide ideal systems to directly study frustration. We have examined with photoemission electron microscopy the magnetic configurations three basic building blocks an artificial kagome spin ice consisting one, two, and rings. The arrangement is particularly interesting because it highly frustrated interactions at a vertex are equivalent. Employing energy calculations, we able make full characterization states...
The Surface/Interface: Microscopy beamline of the Swiss Light Source started operation in 2001. In 2007 has been significantly upgraded with a second refocusing section and blazed grating optimized for high photon flux. Two Apple II type undulators plane monochromator using collimated light scheme deliver photons an energy from 90eV to about 2keV variable polarization photoemission electron microscope (PEEM) as primary user station. We measured focus (45×60) μm(ν×h) flux > 1012 photon/s all...
Artificial multiferroic systems, in which novel properties can emerge from elastic coupling between piezoelectric and magnetostrictive phases, are a promising route to obtain significant room-temperature magnetoelectric at the nanoscale. In this work, we have used element-specific soft x-ray photoemission electron microscopy spatially resolve effects of ferroelectric BaTiO${}_{3}$ on magnetic ferromagnetic layers CoFe${}_{2}$O${}_{4}$ NiFe${}_{2}$O${}_{4}$. Resulting large magnetoelastic...
The unidirectional motion of information carriers such as domain walls in magnetic nanostrips is a key feature for many future spintronic applications based on shift registers. This ratchet effect has so far been achieved limited number complex nanomagnetic structures, example, by lithographically engineered pinning sites. Here we report simple remagnetization originated the asymmetric potential from designed increasing lengths magnetostatically coupled ferromagnetic segments FeCo/Cu...
The effective superparamagnetic behaviour in IONF is caused by the near demagnetized state driven high vorticity of core moment texture at low magnetic fields.
We investigated the influence of interface orientation on magnetic coupling for (110), (001), and (111) interfaces epitaxial NiO thin films single-crystal ${\text{Fe}}_{3}{\text{O}}_{4}$. In our analysis, we combine x-ray spectroscopies with circularly linearly polarized light, i.e., circular linear dichroism (XMCD XMLD). A full treatment anisotropic XMLD in single-crystalline materials backed by theoretical support allows a reliable vectorial magnetometry. Both (110) produce collinear...
By direct imaging we determine spin structure changes in Permalloy wires and disks due to transfer torque as well the critical current densities for different domain wall types. Periodic transformations from transverse vortex walls vice versa are observed, transformation mechanism occurs by core displacement perpendicular wire. The results imply that nonadiabaticity parameter beta does not equal damping alpha, agreement with recent theoretical predictions. motion is further studied revealing...
The surface sensitivity of X-ray Magnetic Circular Dichroism in extreme conditions is exploited to investigate the first layers bulk single-molecule magnets (SMM). Striking differences emerge between two classes SMM with different structural constraints, thus highlighting importance molecular design realization spintronic devices
The electrical transport and resistance switching mechanism in amorphous carbon (a-C) is investigated at the nanoscale. conduction a-C thin films shown to be captured well by a Poole–Frenkel model that involves nonisolated traps. Moreover, high electric fields field-induced threshold phenomenon observed. following change attributed Joule heating subsequent localized thermal annealing. We demonstrate mostly due clustering of existing sp2 sites within sp3 matrix. behaviour,...
The surface and the internal magnetic structure of bamboo-like cylindrical nanowires with tailored diameter modulations have been determined by XMCD/PEEM MFM.
X-ray photoemission electron microscopy combined with x-ray magnetic circular dichroism is used to study the properties of individual iron nanoparticles sizes ranging from 20 down 8 nm. While magnetocrystalline anisotropy bulk suggests superparamagnetic behavior in this size range, ferromagnetically blocked particles are also found at all sizes. Spontaneous transitions state observed single and suggest that enhanced energy barriers ferromagnetic due metastable, structurally excited states...
Using photoemission electron microscopy, we study the magnetization orientation in single 5-25 nm iron particles coupled to a ferromagnetic cobalt support. We find noncollinear alignment between particle and substrate above size of approximately 6 parallel for smaller sizes. Numerical calculations reveal transition from an exchange-dominated anisotropy-dominated regime on increasing height: are single-domain collinear state while larger exhibit spin-spiral magnetic structure determined by...
Artificial spin-ice systems consisting of nanolithographic arrays isolated nanomagnets are model for the study frustration-induced phenomena. We have recently demonstrated that monopoles and Dirac strings can be directly observed via synchrotron-based photoemission electron microscopy, where magnetic state individual nanoislands imaged in real space. These experimental results string formation excellent agreement with Monte Carlo simulations hysteresis an array dipoles situated on a kagome...
Arrays of monodisperse colloidal 11.4-nm Co nanoparticles were investigated by multifrequency ferromagnetic resonance and x-ray magnetic circular dichroism (XMCD). The ratio orbital-to-spin moment ${\ensuremath{\mu}}_{L}/{\ensuremath{\mu}}_{S}^{\mathrm{eff}}=0.24\ifmmode\pm\else\textpm\fi{}0.06$ determined XMCD is 300% enhanced in comparison to the obtained from a $g$-factor analysis which yields $g=2.150\ifmmode\pm\else\textpm\fi{}0.015$ corresponding...
We present experimental evidence of transverse magnetic domains, previously observed only in nanostrips, CoNi cylindrical nanowires with designed crystal symmetry and tailored anisotropy. The domains are found together more conventional vortex along the same nanowire, denoting a bistable system similar energies. surface inner magnetization distribution both types analyzed by photoemission electron microscopy x-ray circular dichroism contrast, hysteresis loop individual measured...
We present a systematic investigation of the optical response to circularly polarized illumination in twisted stacked plasmonic nanostructures. The system consissts two identical, parallel gold triskelia centrally aligned and rotated at central angle relative each other. Sample fabrication was acomplished through double electron beam lithograpy process. This stack holds modes multipolar character near-infrared range, showing strong dependence their excitation intensities on handedness...
The reduction in symmetry associated with the onset of ferroelectric order ${\text{PbZr}}_{0.2}{\text{Ti}}_{0.8}{\text{O}}_{3}$ (PZT) thin films leads to a pronounced difference at $\text{Ti}\text{ }{L}_{3,2}$ absorption edges between spectra measured x-ray linear polarization perpendicular and parallel polarization. We introduce general method analyze observed using atomic multiplet calculations. Moreover, we find experimental evidence for structural changes PZT induced by reversal