Search results for "RILL"
showing 10 items of 1272 documents
Heisenberg Exchange and Dzyaloshinskii–Moriya Interaction in Ultrathin Pt(W)/CoFeB Single and Multilayers
2021
We present results of the analysis of Brillouin light-scattering (BLS) measurements of spin waves performed on ultrathin single and multirepeat CoFeB layers with adjacent heavy metal layers. From a detailed study of the spin-wave dispersion relation, we independently extract the Heisenberg exchange interaction (also referred to as symmetric exchange interaction), the Dzyaloshinskii–Moriya interaction (DMI, also referred to as antisymmetric exchange interaction), and the anisotropy field. We find a large DMI in CoFeB thin films adjacent to a Pt layer and nearly vanishing DMI for CoFeB films adjacent to a W layer. Furthermore, the influence of the dipolar interaction on the dispersion relatio…
Biomechanical evaluation of oversized drilling technique on primary implant stability measured by insertion torque and resonance frequency analysis
2015
Background This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA). Material and Methods Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant s…
Large Dzyaloshinskii-Moriya interaction and room-temperature nanoscale skyrmions in CoFeB/MgO heterostructures
2021
Summary Magnetic skyrmions in heavy metal (HM)/CoFeB/MgO structures are of particular interest for skyrmion-based magnetic tunnel junction (MTJ) devices because of their reliable generation, stability, and readout through purely electrical methods. To optimize the properties, such as stability, a strong Dzyaloshinskii-Moriya interaction (DMI) is required at room temperature. Here, using first-principles calculations, we demonstrate that huge DMI can be obtained in Ir/CoFe structures with an Fe-terminated configuration. Moreover, Brillouin light-scattering measurements show that indeed Ta/Ir/Co20Fe60B20/MgO thin films with perpendicular magnetic anisotropy exhibit a large DMI value (1.13 mJ/…
Effect of annealing on Co2FeAl0.5Si0.5thin films: A magneto-optical and x-ray absorption study
2011
A series of Al and MgO-capped Co${}_{2}$FeAl${}_{0.5}$Si${}_{0.5}$ epitaxial thin films grown on MgO with various levels of L2${}_{1}$ ordering was obtained by in situ annealing. The films were studied by means of x-ray absorption spectroscopy, x-ray magnetic circular dichroism (XMCD), magneto-optical Kerr effect magnetometry, and Brillouin light scattering. We find the anisotropy constants decrease, while the spin wave stiffness increases as the samples are annealed to higher temperatures. The magnetization as determined by Brillouin light scattering reveals a maximum value at intermediate annealing temperatures. Surprisingly, the orbital-to-spin-moment ratio (as seen from XMCD) is essenti…
Phonon Dispersion of Wurtzite CdSe: The Bond Charge Model
2000
The phonon dispersion of wurtzite CdSe is presented along the main directions of the Brillouin zone. The study has been performed by using a bond charge model for wurtzite-type semiconductors with only six adjustable parameters. The results are compared against neutron scattering data and ab initio calculations. The phonon eigenvectors corresponding to the vibrational modes at the Γ-point are in very good agreement with the ab initio calculations.
Elastic and piezoelectric properties of BaTiO3 at room temperature
1999
Abstract We have calculated the phonon dispersion curves of barium titanate (BaTiO 3 ) at room temperature. A lattice dynamical formalism using the shell model is used. This microscopic model includes the short-range interactions of axially symmetric type and the long-range Coulomb interactions and taking into account the electronic polarizability of constituent ions. Zone center phonon and a few phonons in the first Brillouin zone are used for fitting. The values of relevant parameters are critically analyzed. A calculation of the elastic and piezoelectric properties is presented and compared with the available experimental data.
Surface resonance of thin films of the Heusler half-metal Co2MnSi probed by soft x-ray angular resolved photoemission spectroscopy
2019
Heusler compounds are promising materials for spintronics with adjustable electronic properties including 100% spin polarization at the Fermi energy. We investigate the electronic states of ${\mathrm{AlO}}_{x}$ capped epitaxial thin films of the ferromagnetic half-metal ${\mathrm{Co}}_{2}\mathrm{MnSi}$ ex situ by soft x-ray angular resolved photoemission spectroscopy (SX-ARPES). Good agreement between the experimental SX-ARPES results and photoemission calculations including surface effects was obtained. In particular, we observed in line with our calculations a large photoemission intensity at the center of the Brillouin zone, which does not originate from bulk states, but from a surface r…
Molecular dynamics of carrageenan composites reinforced with Cloisite Na+ montmorillonite nanoclay
2017
[EN] Nanocomposites comprising biodegradable carrageenan and glycerol(KCg) as the host polymer, with different contents of natural montmorillonite (MMT) as filler, were prepared by a solution casting process. Different techniques have been used to determine the interaction/behavior among the different components of the samples such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscope (TEM) and, mainly, Dielectric relaxation spectroscopy (DRS). FTIR indicates hydrogen interaction between carrageenan matrix and silicate that is confirmed by the XRD data indicating some kind of carrageenan intercalation between the MMT layers. A rather ho…
Effect of Chitin Whiskers on the Molecular Dynamics of Carrageenan-Based Nanocomposites
2019
[EN] Films of carrageenan (KC) and glycerol (g) with different contents of chitin nanowhiskers (CHW) were prepared by a solution casting process. The molecular dynamics of pure carrageenan (KC), carrageenan/glycerol (KCg) and KCg with different quantities of CHWs as a filler was studied using dielectric relaxation spectroscopy. The analysis of the CHW effect on the molecular mobility at the glass transition, T-g, indicates that non-attractive intermolecular interactions between KCg and CHW occur. The fragility index increased upon CHW incorporation, due to a reduction in the polymer chains mobility produced by the CHW confinement of the KCg network. The apparent activation energy associated…
Mechanical Coupling in Gold Nanoparticles Supermolecules Revealed by Plasmon-Enhanced Ultralow Frequency Raman Spectroscopy
2016
International audience; Acoustic vibrations of assemblies of gold nanoparticles were investigated using ultralow frequency micro-Raman scattering and finite element simulations. When exciting the assemblies resonantly with the surface plasmon resonance of electromagnetically coupled nano-particles, Raman spectra present an ultralow frequency band whose frequency lies below the lowest Raman active Lamb mode of single nanoparticles that was observed. This feature was ascribed to a Raman vibration mode of gold nanoparticle " supermolecules " , that is, nanoparticles mechanically coupled by surrounding polymer molecules. Its measured frequency is inversely proportional to the nanoparticle diame…