Search results for "Paramagnetic"
showing 10 items of 600 documents
Power saturation of ESR signal in ammonium tartrate exposed to 60Co gamma-ray photons, electrons and protons.
2006
Abstract Marrale, M., Brai, M., Triolo, A., Bartolotta, A. and D'Oca, M. C. Power Saturation of ESR Signal in Ammonium Tartrate Exposed to 60Co γ-Ray Photons, Electrons and Protons. Radiat. Res. 166, 802–809 (2006). In this paper we present an investigation of the electron spin resonance (ESR) line shape of ammonium tartrate (AT) dosimeters exposed to radiation with different linear energy transfer (LET). We exposed our dosimeters to γ-ray photons (60Co), 7 MeV and 14 MeV initial energy electrons, and 19.3 MeV initial energy protons. The differences in the power saturation behavior of ESR spectra of AT irradiated with photons, electrons and protons could be correlated to the effective LET o…
Photoelectrical detection of electron spin resonance of nitrogen-vacancy centres in diamond
2015
The protocols for the control and readout of Nitrogen Vacancy (NV) centres electron spins in diamond offer an advanced platform for quantum computation, metrology and sensing. These protocols are based on the optical readout of photons emitted from NV centres, which process is limited by the yield of photons collection. Here we report on a novel principle for the detection of NV centres magnetic resonance in diamond by directly monitoring spin-preserving electron transitions through measurement of NV centre related photocurrent. The demonstrated direct detection technique offers a sensitive way for the readout of diamond NV sensors and diamond quantum devices on diamond chips. The Photocurr…
Characterization ofE′δand triplet point defects in oxygen-deficient amorphous silicon dioxide
2006
We report an experimental study by electron paramagnetic resonance (EPR) of $\ensuremath{\gamma}$-ray irradiation induced point defects in oxygen deficient amorphous $\mathrm{Si}{\mathrm{O}}_{2}$ materials. We have found that three intrinsic ($\mathrm{E}^{\ensuremath{'}}{}_{\ensuremath{\gamma}}$, $\mathrm{E}^{\ensuremath{'}}{}_{\ensuremath{\delta}}$, and triplet) and one extrinsic $({[\mathrm{Al}{\mathrm{O}}_{4}]}^{0})$ paramagnetic centers are induced. All the paramagnetic defects but $\mathrm{E}^{\ensuremath{'}}{}_{\ensuremath{\gamma}}$ center are found to reach a concentration limit value for doses above ${10}^{3}\phantom{\rule{0.3em}{0ex}}\mathrm{kGy}$, suggesting a generation process f…
Strong reduction of the Korringa relaxation in the spin-density wave regime ofEuFe2As2observed by electron spin resonance
2010
Electron spin resonance measurements in ${\text{EuFe}}_{2}{\text{As}}_{2}$ single crystals revealed an absorption spectrum of a single resonance with Dysonian line shape. Above the spin-density wave (SDW) transition at ${T}_{\text{SDW}}=190\text{ }\text{K}$ the spectra are isotropic and the Eu spins relax via the conduction electrons resulting in a Korringa-type increase in the linewidth. Below ${T}_{\text{SDW}}$, a distinct anisotropy develops and the relaxation behavior of the Eu spins changes drastically into one with characteristic properties of a magnetic insulating system, where dipolar and crystal-field interactions dominate. This indicates a spatial confinement of the conduction ele…
Instantaneous diffusion in spin-echo dynamics: A frequency-domain experimental investigation.
1992
We report an experimental investigation on the spectral content of the echo radiation emitted by an electron spin system excited by a two-pulse sequence. The measurements are carried out at liquid-helium temperature in a sample of quartz containing a very low concentration of [${\mathrm{AlO}}_{4}$${]}^{0}$ centers, in which instantaneous diffusion mechanism makes the main contribution to the phase relaxation. The experimental spectral shapes reproduce the theoretical ones, as calculated for an ideal system of noninteracting spins. However, the agreement is only qualitative, as the experimental spectral widths are found to be less than expected by a factor that depends on the exciting sequen…
Electron paramagnetic resonance study of theCe3+pair centers inYAlO3:Ce scintillator crystals
2015
Single crystals of $\mathrm{YAl}{\mathrm{O}}_{3}$ doped with Ce have been studied by electron paramagnetic resonance (EPR) at the 9.4 and 34 GHz microwave bands. Besides the single-ion $\mathrm{C}{\mathrm{e}}^{3+}$ spectrum, measurements have revealed many satellite lines which belong to the $\mathrm{C}{\mathrm{e}}^{3+}\text{\ensuremath{-}}\mathrm{C}{\mathrm{e}}^{3+}$ pair centers. Their spectra have been fitted by a general effective spin Hamiltonian describing two interacting particles with the spin $S=1/2$. Corresponding $g$ factors and spin-spin coupling constants have been determined. The spin-spin coupling constants are in the range from 0.1 up to $0.65\phantom{\rule{0.16em}{0ex}}\mat…
Optical absorption band at5.8eVassociated with theEγ′centers in amorphous silicon dioxide: Optical absorption and EPR measurements
2008
Line shape modifications induced by thermal treatment in the optical absorption and electron paramagnetic resonance (EPR) signals associated with the ${E}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ center are experimentally investigated in various types of $\ensuremath{\gamma}$-irradiated amorphous silicon dioxide $(a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2})$. The $g$ values of the EPR main resonance line of the ${E}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ center show a shift correlated with the peak energy variation of the absorption band at about $5.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ associated with this defect. These spectroscopic changes are proposed to originate from structu…
Si29Hyperfine Structure of theE′αCenter in Amorphous Silicon Dioxide
2006
We report a study by electron paramagnetic resonance on the $E^{\ensuremath{'}}{}_{\ensuremath{\alpha}}$ point defect in amorphous silicon dioxide ($a\mathrm{\text{\ensuremath{-}}}{\mathrm{SiO}}_{2}$). Our experiments were performed on $\ensuremath{\gamma}$-ray irradiated oxygen-deficient materials and pointed out that the $^{29}\mathrm{Si}$ hyperfine structure of the $E^{\ensuremath{'}}{}_{\ensuremath{\alpha}}$ consists of a pair of lines split by $\ensuremath{\sim}49\text{ }\text{ }\mathrm{mT}$. On the basis of the experimental results, a microscopic model is proposed for the $E^{\ensuremath{'}}{}_{\ensuremath{\alpha}}$ center, consisting of a hole trapped in an oxygen vacancy with the un…
Coherent manipulation of three-qubit states in a molecular single-ion magnet
2017
We study the quantum spin dynamics of nearly isotropic Gd3+ ions entrapped in polyoxometalate molecules and diluted in crystals of a diamagnetic Y3+ derivative. The full energy-level spectrum and the orientations of the magnetic anisotropy axes have been determined by means of continuous-wave electron paramagnetic resonance experiments, using X-band (9-10 GHz) cavities and on-chip superconducting waveguides and 1.5-GHz resonators. The results show that seven allowed transitions between the 2S+1 spin states can be separately addressed. Spin coherence T2 and spin-lattice relaxation T1 rates have been measured for each of these transitions in properly oriented single crystals. The results sugg…
Direct Identification of Dilute Surface Spins on Al2O3 : Origin of Flux Noise in Quantum Circuits
2017
An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al2O3. We measure a spin density of 2.2×1017 spins/m2, attributed to physisorbed atomic hydrogen and S=1/2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices.