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Magnetic-field-dependent quantum emission in hexagonal boron nitride at room temperature
摘要： Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.
关键词： photoluminescence,room temperature,quantum emitters,magnetic field,hexagonal boron nitride,spin defects
更新于2025-09-23 15:22:29
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Fabrication, electrical and magnetic properties of 0.7(BiGd <sub/>x</sub> Fe <sub/>1?x</sub> O <sub/>3</sub> )?0.3(PbTiO <sub/>3</sub> ) composites
摘要： The polycrystalline samples having chemical formula 0.7(BiGdxFe1?xO3)?0.3(PbTiO3) (x = 0.0, 0.05, 0.10, 0.15 and 0.20) were fabricated by using high temperature mixed oxide route. The X-ray diffraction spectra suggested rhombohedral (major) symmetry with small impurity phases. The surface microstructure showed a highly dense packing of grains throughout the wider area for all samples. The dielectric permittivity and loss factor of all samples were studied with the help of temperature-dependent dielectric parameters. The relaxation mechanism was suggested from the dielectric and impedance spectroscopy. The conduction mechanism of all samples was investigated. The P–E and M–H loops of all the samples were taken at room temperature showing the multiferroic properties.
关键词： Dielectric,conductivity,magnetic properties,ferroelectric,impedance
更新于2025-09-23 15:22:29
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Structural characterization of Nd-Fe <sub/>3</sub> O <sub/>4</sub> nanoparticles prepared by hydrothermal synthesis method
摘要： Magnetic nanoparticles of Nd-Fe3O4 were prepared by hydrothermal synthesis method, using NdCl3·6H2O and FeCl3·6H2O as the starting materials in this paper. The structure and morphology of nanoparticles were investigated by XRD, FTIR, EDS and TEM. The results showed that, while the addition of Nd at 10% in mole ratio, resulted in the formation of Nd2O3 crystal peak in cubic Fe3O4 nanocrystallites by XRD. The absorption bands of Fe–O, –OH, –O–C–O– and –CH2– were accordant to the correspondent chemical groups by FTIR. The morphology of the prepared nanoparticles exhibited spherical structure and evenly distributed without agglomeration phenomenon by TEM. The elemental composition were mainly consistent with the precursor materials used in the experiment.
关键词： magnetic nanoparticles,hydrothermal synthesis,Nd-Fe3O4,Structural characterization
更新于2025-09-23 15:22:29
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Epitaxial Growth and Magnetic Properties of NiMnAs Films on GaAs Substrates
摘要： Single-phase Ni0.92Mn1.08As films with strained C1b symmetry are grown on GaAs (001) substrates. In addition, a preferred epitaxial configuration of (110)-orientated Ni0.92Mn1.08As on (001)-orientated GaAs is revealed by synchrotron radiation measurement. The magnetic properties of the films are found to be significantly influenced by the growth temperature and the optimized growth temperature is determined to be ～370°C. According to the results of x-ray absorption spectroscopy, these phenomena can be attributed to the variation of the local electronic structure of the Mn atoms. Our work provides useful information for the further investigations of NiMnAs, which is a theoretically predicted half-metal.
关键词： epitaxial growth,half-metal,Heusler alloy,magnetic properties,NiMnAs
更新于2025-09-23 15:22:29
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Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering<sup></sup>
摘要： Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering. Co ultrathin films, of various thicknesses (0.8 nm ≤ tCo ≤ 2.5 nm), have been grown by sputtering on Si substrates, using Pt buffer layers and different capping layers (Cu, Ir, MgO and Pt). The x-ray diffraction revealed that our films have a (111) out-of-plane texture with various degrees of strains. Their magnetic properties have been studied by vibrating sample magnetometry (VSM) and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. VSM characterizations revealed that films with Co thickness below (above) the spin reorientation transition thickness, which is capping layer dependent, are perpendicularly (in-plane) magnetized, suggesting the existence of an interface anisotropy. The magnetic dead layer has been taken into account to precisely determine the surface anisotropy constant was found to be 1.42 ± 0.02 erg/cm2 and of 1.33 ± 0.02 erg/cm2 for the Pt/Co/Cu and Pt/Co/Ir samples, respectively, suggesting that it is due to the Pt/Co interface and that the top Co/Cu or Co/Ir interfaces have a negligible contribution. A lower value of 1.07 ± 0.02 erg/cm2 has been obtained for Pt/Co/MgO most probably due to over-oxidation of Co at the Co/MgO interface. The BLS measurements revealed a pronounced nonreciprocal spin waves propagation, due to the interfacial Dzyaloshinskii-Moriya interaction (iDMI) induced by Pt interface with Co, which increases with decreasing Co thickness. The surface iDMI constant Ds estimated at -0.8 pJ/m, -1.05 pJ/m and –0.95 pJ/m, respectively for Pt/Co/Ir, Pt/Co/Cu and Pt/Co/MgO for the samples where a linear thickness dependence of the effective iDMI constant has been observed.
关键词： Dzyaloshinskii-Moriya interaction,Brillouin light scattering,spin waves and Perpendicular magnetic anisotropy,Interface effects
更新于2025-09-23 15:22:29
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Sources of heading errors in optically pumped magnetometers operated in the Earth's magnetic field
摘要： When optically pumped magnetometers are aimed for use in the Earth’s magnetic field, the orientation of the sensor to the field direction is of special importance to achieve accurate measurement results. Measurement errors and inaccuracies related to the heading of the sensor can be an even more severe problem in the case of special operational configurations, such as the use of strong off-resonant pumping. We systematically study the main contributions to the heading error in systems that promise high magnetic field resolutions at the Earth’s magnetic field strengths, namely the nonlinear Zeeman splitting and the orientation-dependent light shift. The good correspondence of our theoretical analysis to experimental data demonstrates that both of these effects are related to a heading-dependent modification of the interaction between the laser light and the dipole moment of the atoms. Also, our results promise a compensation of both effects using a combination of clockwise and counterclockwise circular polarization.
关键词： optically pumped magnetometers,circular polarization,Earth's magnetic field,light shift,nonlinear Zeeman splitting,heading error
更新于2025-09-23 15:22:29
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Conceptual Consequences of the SI
摘要： The SI and its forerunners were largely developed in response to the confusion of multiple electromagnetic unit systems at the start of the 20th century. More than 100 years later, the success of the SI is evidenced by its almost universal acceptance. The adoption of the ampere as the fourth base unit has proved to be a beneficial way of simplifying electromagnetic units. However, an unintended consequence of adopting this system has been the development of several misconceptions regarding the physics of electromagnetic quantities. The anticipated educational activities associated with the upcoming SI redefinition offer an ideal opportunity to resolve this concern.
关键词： CGS,Permeability of Free Space,SI,Ampere,Magnetic Constant,Electrical Units
更新于2025-09-23 15:22:29
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Synthesis and Properties of Novel Thiophene-Based Liquid Crystalline Conducting Polymers
摘要： Side-chain liquid crystalline polythiophenes were synthesised and the effects of the mesogenic units on the structure and electronic properties of the polymers were studied. The liquid crystal properties of the polymer films were studied using polarised hot-stage optical microscopy and differential scanning calorimetry, and X-ray diffractometry was used to investigate the effect of a magnetic field on the monomers and polymers.
关键词： Polythiophene,Conducting polymers,Liquid crystals,X-ray diffraction,Magnetic field
更新于2025-09-23 15:22:29
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Distortion of Magnetic Fields in a Starless Core. V. Near-infrared and Submillimeter Polarization in FeSt 1-457
摘要： The relationship between submillimeter dust emission polarization and near-infrared (NIR) H-band polarization produced by dust dichroic extinction was studied for the cold starless dense core FeSt 1–457. The distributions of polarization angles (90°-rotated for the submillimeter) and degrees were found to be very different between submillimeter and NIR wavelengths. The mean polarization angles for FeSt 1-457 at submillimeter and NIR wavelengths are 132°. 1 ± 22°. 0 and 2°. 7 ± 16°. 2, respectively. The correlation between PH and AV was found to be linear from the outermost regions to the relatively dense lines of sight of AV ≈ 25 mag, indicating that NIR polarization reflects the overall polarization (magnetic field) structure of the core, at least in this density range. The flat PH/AV versus AV correlations were confirmed, and the polarization efficiency was found to be comparable to the observational upper limit. On the other hand, as reported by Alves et al. submillimeter polarization degrees show a clear linearly decreasing trend against AV from AV ≈ 20 mag to the densest center (AV ≈ 41 mag), appearing as a 'polarization hole' structure. The power-law index for the Psubmm versus AV relationship was obtained to be ≈?1, indicating that the alignment for the submillimeter-sensitive dust is lost. These very different polarization distributions at submillimeter and NIR wavelengths suggest either that (1) there are different radiation environments at these wavelengths or (2) submillimeter-sensitive dust is localized or (3) a combination of both.
关键词： polarization,dust, extinction,stars: magnetic field,ISM: clouds,stars: formation
更新于2025-09-23 15:22:29
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A Quasi-periodic Propagating Wave and Extreme-ultraviolet Waves Excited Simultaneously in a Solar Eruption Event
摘要： Quasi-periodic fast-propagating (QFP) magnetosonic waves and extreme-ultraviolet (EUV) waves were proposed to be driven by solar flares and coronal mass ejections (CMEs), respectively. In this Letter, we present a detailed analysis of an interesting event in which we find that both QFP magnetosonic waves and EUV waves are excited simultaneously in one solar eruption event. The co-existence of the two wave phenomena offers an excellent opportunity to explore their driving mechanisms. The QFP waves propagate in a funnel-like loop system with a speed of 682–837 km s-1 and a lifetime of 2 minutes. On the contrary, the EUV waves, which present a faster component and a slower component, propagate in a wide angular extent, experiencing reflection and refraction across a magnetic quasi-separatrix layer. The faster component of the EUV waves travels with a speed of 412–1287 km s-1, whereas the slower component travels with a speed of 246–390 km s-1. The lifetime of the EUV waves is ～15 minutes. It is revealed that the faster component of the EUV waves is cospatial with the first wavefront of the QFP wave train. The QFP waves have a period of about 45 ± 5 s, which is absent in the associated flares. All of these results imply that QFP waves can also be excited by mass ejections, including CMEs or jets.
关键词： Sun: oscillations,waves,Sun: flares,Sun: corona,Sun: magnetic fields
更新于2025-09-23 15:22:29