- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Synthesis of yttrium iron garnet/bismuth quantum dot heterostructures with localized plasmon enhanced magneto-optical performance
摘要： Interactions between light and magnetic matter attracted great attention lately due to their potential applications in nanophotonics, spintronics, and high-accuracy sensing. Here, we grew bismuth quantum dots (Bi–QDs) with strong spin–orbit coupling on a magnetic insulator yttrium iron garnet (YIG) via molecular beam epitaxy. The YIG/Bi–QDs material shows an enhanced magneto-optical Kerr rotation up to 130 % compared with that of a bare YIG film. The Bi–QDs were also introduced onto a lutetium–bismuth co-doped YIG film to form a hybrid system with remarkably enhanced Kerr rotation (from 1626 to 2341 mdeg). Ferromagnetic resonance measurements showed an increased effective magnetization as well as interfacial spin–orbit field in the YIG/Bi–QD heterostructures. Localized plasmons were mapped using electron energy loss spectroscopy with high spatial resolution, revealing enhanced plasmon intensity at both the Bi–QD surface and YIG/Bi–QD interface. Introducing Bi-QDs onto the YIG film enhanced Kerr rotation owing to the attenuated optical reflection and increased effective magnetization. The Bi–QD-enhanced magneto-optical effect enables development of efficient nanoscale light switching, spintronics, and even plasmonic nano-antennas.
关键词： Electron energy loss spectroscopy,Surface plasmon resonance,Bismuth quantum dot,Ferromagnetic resonance,Magneto-optical materials
更新于2025-09-23 15:21:01
-
Ultrathin films of L1 <sub/>0</sub> -MnAl on GaAs (001): A hard magnetic MnAl layer onto a soft Mn-Ga-As-Al interface
摘要： Ferromagnetic MnAl (L10-MnAl phase) ultrathin films with thickness varying from 1 to 5 nm have been epitaxially grown on a GaAs (001) substrate. A coercivity above 8 kOe has been obtained with no need of a buffer layer by tuning the sample preparation and the growth parameters. Surface and interface analysis carried out by in situ characterization techniques (x-ray photoelectron spectroscopy and low energy electron diffraction), available in the molecular beam epitaxy chamber, has shown the formation of a ferromagnetic interface consisting of Mn-Ga-As-Al, which contribution competes with the MnAl alloyed film. The appearance of this interface provides important information to understand the growth mechanism of MnAl-based films reported in the literature.
关键词： x-ray photoelectron spectroscopy,ferromagnetic,GaAs,molecular beam epitaxy,low energy electron diffraction,ultrathin films,L10-MnAl
更新于2025-09-23 15:21:01
-
Ferromagnetic Properties of N-Doped and Undoped TiO2 Rutile Single-Crystal Wafers with Addition of Tungsten Trioxide
摘要： In this work, undoped, N-doped, WO3-loaded undoped, and WO3-loaded with N-doped TiO2 rutile single-crystal wafers were fabricated by direct current (DC) magnetron sputtering. N-doping into TiO2 and WO3 loading onto TiO2 surface were used to increase and decrease oxygen vacancies. Various measurements were conducted to analyze the structural and magnetic properties of the samples. X-ray diffraction results showed that the N-doping and WO3 loading did not change the phase of all samples. X-ray photoelectron spectroscopy results revealed that W element loaded onto rutile single-crystal wafers existed in the form of WO3. UV-Vis spectrometer results showed that the absorption edge of WO3-loaded undoped and WO3-loaded with N-doped TiO2 rutile single-crystal wafers had red shift, resulting in a slight decrease in the corresponding band gap. Photoluminescence spectra indicated that oxygen vacancies existed in all samples due to the postannealing atmosphere, and oxygen vacancies density increased with N-doping, while decreasing with WO3 loading onto TiO2 surface. The magnetic properties of the samples were investigated, and the saturation magnetization values were in the order N-doped > WO3-loaded with N-doped > undoped > WO3-loaded undoped rutile single-crystal wafers, which was the same order as the oxygen vacancy densities of these samples. N-doping improved the saturation magnetization values, while WO3-loaded decreased the saturation magnetization values. This paper reveals that the magnetic properties of WO3-loaded with N-doped rutile single-crystal wafers originate from oxygen vacancies.
关键词： rutile TiO2 single-crystal wafers,WO3-loaded,oxygen vacancy,ferromagnetic properties
更新于2025-09-23 15:21:01
-
Input Filter Capacitance and Inductance Design for Photovoltaic Systems
摘要： A conformal permeable toroidal antenna operating in both a vertically polarized monopole mode and circularly polarized (CP) dipole mode in the UHF frequency range is designed based on theory of magneto-dielectric radiators. This antenna has been fabricated using a new advanced ferromagnetic laminate composite material whose high impedance and anisotropic properties enable an antenna that radiates via magnetic currents. The antenna, less than 0.5 m in diameter and less than 2 cm thick, was fabricated and tested. Including the imperfections of the feed network and a simple matching scheme, the antenna operates from 200 to 500 MHz with an input match of better than 10 dB, CP dipole realized gain as high as 2 dBi, and monopole mode vertically polarized gain as high as 1 dBi.
关键词： multifunction antenna,ferromagnetic materials,multimode antenna,wideband antenna,Conformal antennas
更新于2025-09-23 15:19:57
-
3 Practical uses for topological photonics: An obscure phenomenon could improve chips, lasers, and quantum circuitry
摘要： A conformal permeable toroidal antenna operating in both a vertically polarized monopole mode and circularly polarized (CP) dipole mode in the UHF frequency range is designed based on theory of magneto-dielectric radiators. This antenna has been fabricated using a new advanced ferromagnetic laminate composite material whose high impedance and anisotropic properties enable an antenna that radiates via magnetic currents. The antenna, less than 0.5 m in diameter and less than 2 cm thick, was fabricated and tested. Including the imperfections of the feed network and a simple matching scheme, the antenna operates from 200 to 500 MHz with an input match of better than 10 dB, CP dipole realized gain as high as 2 dBi, and monopole mode vertically polarized gain as high as 1 dBi.
关键词： Conformal antennas,ferromagnetic materials,multimode antenna,multifunction antenna,wideband antenna
更新于2025-09-23 15:19:57
-
Photon-Assisted Heat Generation by Electric Current in a Quantum Dot Attached to Ferromagnetic Leads
摘要： Heat generated by electric current in a quantum dot device contacting a phonon bath is studied using the non-equilibrium Green function technique. Spin-polarized current is generated owing to the Zeeman splitting of the dot level. The current’s strength and the spin polarization are further manipulated by changing the frequency of an applied photon field and the ferromagnetism on the leads. We find that the associated heat by this spin-polarized current emerges even if the bias voltage is smaller than the phonon energy quanta and obvious negative differential of the heat generation develops when the photon frequency exceeds that of the phonon. It is also found that both the strength and the resonant peaks’ position of the heat generation can be tuned by changing the value and the arrangement configurations of the magnetic moments of the two leads, and then provides an effective method to generate large spin-polarized current with weak heat. Such a result may be useful in designing low energy consumption spintronic devices.
关键词： quantum dot,heat generation,ferromagnetic leads,photon-assisted tunneling,spin-polarized current
更新于2025-09-23 15:19:57
-
Colossal dielectric, relaxor ferroelectric, diamagnetic and weak ferromagnetic properties of NdCrO3 perovskite nanoparticles
摘要： The NdCrO3 perovskite nanoparticles have been successfully synthesized using sol–gel auto-combustion process. Structural and morphological characterizations of the material have been performed at room temperature using XRD and SEM, respectively. Frequency- and temperature-dependent dielectric measurements have been performed in the range of 1 Hz–10 MHz and RT - 300 °C, respectively. The dielectric constant is found to be in the order of e0 > 103 at room temperature, indicating the colossal dielectric constant behaviour. Ferroelectric phase transition temperature has increased with an increase in frequency, suggesting that the material is a relaxor ferroelectric nature. Temperature- and field-dependent magnetization measurements have been carried out in the temperature range (5–400 K) and field up to 5 T. M–T curve exhibited a diamagnetic-like behaviour in low temperature and low fields. Two magnetic transitions were found at TN1 (223 K) and TN2 (33 K) which correspond to para to weak ferromagnetic transition and Nd3+ spin ordering, respectively. Hysteresis loop noticed weak ferromagnetism.
关键词： weak ferromagnetic properties,relaxor ferroelectric,Colossal dielectric,diamagnetic,NdCrO3 perovskite nanoparticles
更新于2025-09-23 15:19:57
-
Field Characteristics of Spin-Torque Diode Sensitivity in the Presence of a Bias Current
摘要： The use of the spin-torque diode effect, which is generated upon the current-induced transfer of spin angular momentum in magnetic tunnel junctions, opens the prospect of considerably improving microwave sensitivity in the gigahertz frequency band over that of semiconductor Schottky diodes. In this work, the spin-diode effect of microwave signal rectification in a magnetic tunnel junction upon the resonant excitation of spin waves in the free magnetic layer as a result of the current-induced spin-transfer torque effect is analyzed theoretically. Frequency characteristics of the resonant response of a spin-torque diode to a microwave signal are calculated in the linear macrospin approximation as functions of the direction and value of the applied magnetic field and bias current. It is shown that with zero bias current, the maximum rectified voltage across a junction is obtained in the geometry of mutually perpendicular magnetizations of magnetic layers; as the resonant frequency of oscillations in a magnetic field increases, this voltage drops at the retained equilibrium orientation of spins in the layers. After the bias current is switched on, the resonance amplitude of forced oscillations of the free layer spins upon microwave excitation grows sharply at the critical point of the spin-torque diode's loss of equilibrium state stability. The linewidth at this point is limited only by nonlinear effects. Improving spin-torque diode sensitivity is important for its use in microwave holographic vision systems.
关键词： macrospin model,microwave sensitivity,ferromagnetic resonance,magnetic tunnel junction,portable spin-torque diode
更新于2025-09-19 17:15:36
-
Spin excitations in laser-molecular-beam epitaxy grown nanosized YIG films: towards low relaxation and desirable magnetization profile
摘要： We describe synthesis of nanosized Y3Fe5O12 (YIG) films grown by laser-molecular-beam epitaxy on Gd3Ga5O12 (GGG) and Nd3Ga5O12 (NdGG) substrates with (111) orientation and present results of ferromagnetic resonance (FMR) and spin wave propagation studies in these heterostructures. It is found that magnetic parameters of YIG films grown on NdGG and GGG substrates are considerably different. FMR spectra of YIG/NdGG structures are characterized by a large number of narrow peaks, while FMR spectra of YIG/GGG structures consist of a small number of peaks or one peak. The effective magnetization of YIG films grown on NdGG substrates is less than that of YIG films grown on GGG and is more sensitive to the growth conditions. A lateral inhomogeneity of YIG/NdGG structures is observed in spin wave propagation experiments. For YIG/NdGG and YIG/GGG structures the FMR linewidth ?H of a single peak sharply increases with temperature decrease from 298 to 67 K. The observed increase of ?H is explained by typical relaxation processes caused by the presence of Fe2+ ions. From the spin-wave propagation study it is also found that relaxation of spin-waves explains only a minor part of the FMR single peak linewidth in YIG/NdGG structures. On the basis of obtained results, YIG/GGG/semiconductor- and YIG/NdGG/semiconductor-heterostructures with expected low spin-wave relaxation and desirable effective magnetization profile are proposed.
关键词： magnetization profile,ferromagnetic resonance,spin wave propagation,laser-molecular-beam epitaxy,YIG films
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Cost-Effective Snow Removal from Solar Panels
摘要： A conformal permeable toroidal antenna operating in both a vertically polarized monopole mode and circularly polarized (CP) dipole mode in the UHF frequency range is designed based on theory of magneto-dielectric radiators. This antenna has been fabricated using a new advanced ferromagnetic laminate composite material whose high impedance and anisotropic properties enable an antenna that radiates via magnetic currents. The antenna, less than 0.5 m in diameter and less than 2 cm thick, was fabricated and tested. Including the imperfections of the feed network and a simple matching scheme, the antenna operates from 200 to 500 MHz with an input match of better than 10 dB, CP dipole realized gain as high as 2 dBi, and monopole mode vertically polarized gain as high as 1 dBi.
关键词： ferromagnetic materials,wideband antenna,multimode antenna,multifunction antenna,Conformal antennas
更新于2025-09-16 10:30:52