Search results for "engineering.material"
showing 10 items of 2352 documents
Demonstration of diamond nuclear spin gyroscope
2021
Description
Miniature Cavity-Enhanced Diamond Magnetometer
2017
We present a highly sensitive miniaturized cavity-enhanced room-temperature magnetic-field sensor based on nitrogen-vacancy (NV) centers in diamond. The magnetic resonance signal is detected by probing absorption on the 1042\,nm spin-singlet transition. To improve the absorptive signal the diamond is placed in an optical resonator. The device has a magnetic-field sensitivity of 28 pT/$\sqrt{\rm{Hz}}$, a projected photon shot-noise-limited sensitivity of 22 pT/$\sqrt{\rm{Hz}}$ and an estimated quantum projection-noise-limited sensitivity of 0.43 pT/$\sqrt{\rm{Hz}}$ with the sensing volume of $\sim$ 390 $\mu$m $\times$ 4500 $\mu$m$^{2}$. The presented miniaturized device is the basis for an e…
Electronic structure, localization, and spin-state transition in Cu-substitutedFeSe:Fe1−xCuxSe
2010
We report density-functional studies of the ${\text{Fe}}_{1\ensuremath{-}x}{\text{Cu}}_{x}\text{Se}$ alloy done using supercell and coherent-potential approximation methods. Magnetic behavior was investigated using the disordered local moment approach. We find that Cu occurs in a nominal ${d}^{10}$ configuration and is highly disruptive to the electronic structure of the Fe sheets. This would be consistent with a metal-insulator transition due to Anderson localization. We further find a strong crossover from a weak moment itinerant system to a local moment magnet at $x\ensuremath{\approx}0.12$. We associate this with the experimentally observed jump near this concentration. Our results are …
Charoite, as an example of a structure with natural nanotubes
2012
Charoite from the Murun massif in Yakutiya, Russia (Vorob’ev 2008) was investigated using automated electron diffraction tomography (ADT) (Kolb et al. 2007, 2008; Mugnaioli et al. 2010) and precession electron diffraction (PED) (Mugnaioli et al. 2010, 2009), which allowed to determine the structure of charoite for the first time. The structure was solved ab initio in space group P21/m by direct methods using a fully kinematic approach. The least squares refinements with 2878 reflections F(hkl) >4s F converged to unweighted/weighted residuals R 1/wR 2 • 0.173/0.21 (Rozhdestvenskaya et al. 2010).
Optimizing a Dynamical Decoupling Protocol for Solid-State Electronic Spin Ensembles in Diamond
2015
We demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to 77 K suppresses longitudinal spin relaxation ${T}_{1}$ effects and DD microwave pulses are used to increase the transverse coherence time ${T}_{2}$ from $\ensuremath{\sim}0.7\phantom{\rule{0.28em}{0ex}}\mathrm{ms}$ up to $\ensuremath{\sim}30\phantom{\rule{0.28em}{0ex}}\mathrm{ms}$. We extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we c…
Influence ofsp−dhybridization on the electronic structure of Al-Mn alloys
2008
The influence of $sp\text{\ensuremath{-}}d$ hybridization on the electronic structure of different Al-Mn alloys has been studied by photoelectron spectroscopy. Experimental evidence of a pseudogap in a crystalline binary Hume-Rothery alloy is provided. The pseudogap varies systematically with Mn concentration. The $sp\text{\ensuremath{-}}d$ hybridization alone, even in the absence of Hume-Rothery mechanism, can produce the pseudogap. Existence of the pseudogap, suppression of the $\mathrm{Mn}\phantom{\rule{0.2em}{0ex}}2p$ satellite, and decrease in the Doniach-\ifmmode \check{S}\else \v{S}\fi{}unji\ifmmode \acute{c}\else \'{c}\fi{} asymmetry parameter are the consequences of the $sp\text{\e…
On the half-metallicity of Co2FeSi Heusler alloy: Point-contact Andreev reflection spectroscopy andab initiostudy
2013
Co2FeSi, a Heusler alloy with the highest magnetic moment per unit cell and the highest Curie temperature, has largely been described theoretically as a half-metal. This conclusion, however, disagrees with point contact Andreev reflection (PCAR) spectroscopy measurements, which give much lower values of spin polarization, P. Here, we present the spin polarization measurements of Co2FeSi by the PCAR technique, along with a thorough computational exploration, within the DFT and a GGA+U approach, of the Coulomb exchange U parameters for Co and Fe atoms, taking into account spin-orbit coupling. We find that the orbital contribution (mo) to the total magnetic moment (mT) is significant, since it…
Completely compensated ferrimagnetism and sublattice spin crossing in the half-metallic Heusler compoundMn1.5FeV0.5Al
2017
The Slater-Pauling rule states that $L{2}_{1}$ Heusler compounds with 24 valence electrons never exhibit a total spin magnetic moment. In the case of strongly localized magnetic moments at one of the atoms (here Mn) they will exhibit a fully compensated half-metallic ferrimagnetic state instead, in particular, when symmetry does not allow for antiferromagnetic order. With the aid of magnetic and anomalous Hall effect measurements, it is experimentally demonstrated that ${\mathrm{Mn}}_{1.5}{\mathrm{V}}_{0.5}\mathrm{FeAl}$ follows such a scenario. The ferrimagnetic state is tuned by the composition. A small residual magnetization, which arises due to a slight mismatch of the magnetic moments …
Electronic structure calculations in ordered and disordered solids with spiral magnetic order
2011
A scheme to calculate the electronic structure of systems having a spiral magnetic structure is presented. The approach is based on the Korringa-Kohn-Rostoker Green's function formalism which allows, in combination with the coherent potential approximation alloy theory, dealing with chemically disordered materials. It is applied to the magnetic random alloys Fe${}_{x}$Ni${}_{1\ensuremath{-}x}$, Fe${}_{x}$Co${}_{1\ensuremath{-}x}$, and Fe${}_{x}$Mn${}_{1\ensuremath{-}x}$. For these systems the stability of their magnetic structure was analyzed. For Fe${}_{x}$Ni${}_{1\ensuremath{-}x}$ the spin stiffness for was determined as a function of concentration that was found in satisfying agreement w…
Magnetic configurations in nanostructured Co2MnGa thin film elements
2015
The magnetic configuration of nanostructured elements fabricated from thin films of the Heusler compound Co2MnGa was determined by high-resolution x-ray magnetic microscopy, and the magnetic properties of continuous Co2MnGa thin films were determined by magnetometry measurements. A four-fold magnetic anisotropy with an anisotropy constant of kJ m−3 was deduced, and x-ray microscopy measurements have shown that the nanostructured Co2MnGa elements exhibit reproducible magnetic states dominated by shape anisotropy, with a minor contribution from the magneto-crystalline anisotropy, showing that the spin structure can be tailored by judiciously choosing the geometry.