Double Resonance Peaks Research Articles

Effect of adsorbate viscoelasticity on dynamical responses of laminated microcantilever resonators

Understanding the mechanical properties of bio-adsorbates at the pathological state is important in mechanobiology and medical diagnosis. With the development of biodetection technology, the mechanical properties of bio-adsorbates can be detected at microscale. The paper presents an integro-partial-differential theoretical model to elucidate the effect of adsorbate viscoelasticity on vibrational properties of elastic–viscoelastic microcantilever. A differential method in the temporal domain and a variable separation method or a differential quadrature method (DQM) in the spatial domain are combined to obtain the relevant analytical solutions for free vibration with a complete adsorption and numerical solutions for forced vibration with a local adsorption. The present results agree well with the previous studies in the case of complete elastic adsorption. The study shows that the amplitude of a weakly damped free vibration of the microcantilever is positively correlated with the reciprocal of relaxation time of adsorbate film; the dissipative mechanical property of adsorption film with a standard linear solid constitutive relation endows the forced vibration of the microcantilever subjected to a transverse harmonic load with a double-peak resonance; and the sensitivity of microcantilever-based dynamic detection can be improved remarkably if the excitation frequency, film-to-substrate thickness/modulus ratio, adsorption position/area are carefully controlled.

Self-assembly plasmonic metamaterials based on templated annealing for advanced biosensing.

In this paper, we introduce a novel method for the fabrication of self-assembly plasmonic metamaterials by exploiting fluid instabilities of optical thin films. Due to interplay between template reflow and spinodal dewetting, two metal nanoparticles of different sizes are generated on the top mesas of free-standing porous anodic aluminum oxide (AAO) template, which results in the apprearance of double resonant peaks in the extinction spectrum. These two resonant peaks possess refractive index resolution 3.27 × 10-4 and 2.53 × 10-4 RIU, respectively. This optical intensity modulation based plasmonic nanoplatform shows a dramatically surface sensing performance with outstanding detection capacity of biomolecules, because of the very small decay length of electric field at dual-modes. The detection ability for concanavalin A (Con A) demonstrats that the limit of detection of dual-modes reaches as small as 68 and 79 nM, respectively.

D型对称双芯光子晶体光纤双谐振峰折射率传感器

D型对称双芯光子晶体光纤双谐振峰折射率传感器

Experimental investigation of the suppressed superconducting gap and double-resonance mode in Ba1−xKxFe2As2

$\mathrm{B}{\mathrm{a}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}\mathrm{F}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{2}$ has an exotic physical property, i.e., the ${C}_{2}$ spin-density-wave phase suddenly changes to the ${C}_{4}$ magnetic phase, and superconductivity is suppressed within a narrow composition range around $x=0.25$. We have investigated the doping dependence of the electronic structure of $\mathrm{B}{\mathrm{a}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}\mathrm{F}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{2}$ using angle-resolved photoemission spectroscopy (ARPES), and we found an anomaly in the superconducting (SC) gap structure only for $x=0.25$ in both the hole and electron Fermi surfaces. We also propose that the mechanism of a newly observed double-resonance peak by inelastic neutron scattering is understandable because of the SC gap obtained by ARPES. Our discovery reveals the important relationship between the ${C}_{4}$-magnetic phase and superconductivity, and it provides an opportunity to survey the underlying relationship between the SC gap and the resonance mode in the hole-doped iron-based superconductor.

Stochastic Resonance and Bifurcation of Order Parameter in a Coupled System of Underdamped Duffing Oscillators

The long-term mean-field dynamics of coupled underdamped Duffing oscillators driven by an external periodic signal with Gaussian noise is investigated. A Boltzmann-type [Formula: see text]-theorem is proved for the associated nonlinear Fokker–Planck equation to ensure that the system can always be relaxed to one of the stationary states as time is long enough. Based on a general framework of the linear response theory, the linear dynamical susceptibility of the system order parameter is explicitly deduced. With the spectral amplification factor as a quantifying index, calculation by the method of moments discloses that both mono-peak and double-peak resonance might appear, and that noise can greatly signify the peak of the resonance curve of the coupled underdamped system as compared with a single-element bistable system. Then, with the input signals taken from laboratory experiments, further observations show that the mean-field coupled stochastic resonance system can amplify the periodic input signal. Also, it reveals that for some driving frequencies, the optimal stochastic resonance parameter and the critical bifurcation parameter have a close relationship. Moreover, it is found that the damping coefficient can also give rise to nontrivial nonmonotonic behaviors of the resonance curve, and the resultant resonant peak attains its maximal height if the noise intensity or the coupling strength takes the critical value. The new findings reveal the role of the order parameter in a coupled system of chaotic oscillators.

A superior microwave absorption material: Ni2+-Zr4+ Co-Doped barium ferrite ceramics with large reflection loss and broad bandwidth

Large reflection loss and wide bandwidth are significant targets, determining the microwave absorption ability. However, it is still a challenge to simultaneously satisfy the two conditions. As a multifunctional material, BaFe12O19 possess excellent electromagnetic properties in the microwave frequency band. Due to the natural resonance phenomenon of the material, BaFe12O19 can produce a large magnetic loss which correlates with Fe3+ content, and the microwave absorption characteristics of barium ferrite can be modulated by ion doping. As a typical magnetic metal, Ni coupled with high-valence state Zr4+ doping helps to produce double resonance peaks. In this work, Ni2+-Zr4+ co-doping M-type barium ferrites (BaFe12-2xNixZrxO19, BNZFO-x, x = 0–0.8) were prepared conveniently by solid-state reaction method. Several necessary measurements to characterize its microwave absorption property have been operated such as morphology, magnetic performance and electromagnetic parameters. The results show that reflection loss and bandwidth can be simply tuned by tailoring Ni2+-Zr4+ content. The reflection loss peak drifts from 18 GHz to 9.76 GHz, which involves a half of the studied frequency range. The maximum reflection loss achieves −60.6 dB and the corresponding bandwidth over −10 dB is 7.68 GHz for BNZFO-0.6 ceramic with only 2.1 mm thickness. Thus, the doping of Ni2+-Zr4+ ion pairs is beneficial to improve the absorbing properties of the material, and the superior microwave absorption property may originate from its inner double natural resonance in micro-scale. The excellent microwave absorption properties suggest that BNZFO-x is a promising candidate applied for designing electromagnetic shielding devices.

Application of the HB–AFT method to the primary resonance analysis of a dual-rotor system

This paper focuses on the primary resonance analysis of a dual-rotor system having two rotor unbalance excitations of different rotating speeds and being connected by an inter-shaft ball bearing. Due to the complex excitation condition and the complicated nonlinear bearing forces of the inter-shaft bearing, the general analytical methods, e.g., the multiple scales method or the harmonic balance method, are failed to give the theoretical solutions. Thus, the harmonic balance–alternating frequency/time domain (HB–AFT) method is formulated to deal with this problem. The basic idea of the method is using the inverse discrete Fourier transform and the discrete Fourier transform, instead of the direct analytical relationship between the supposed solutions of the system and the nonlinear forces, to construct the harmonic expressions of the nonlinear forces, which is the so-called alternating frequency/time domain technique. By using the HB–AFT method, therefore, a Newton– Raphson iteration procedure can be performed to demonstrate the approximate solutions of the system. Accordingly, the frequency responses of the system affected by some critical parameters, such as rotating speed ratio, unbalances of both the inner and outer rotors, and clearance of the inter-shaft bearing, are analyzed, respectively. A variety of phenomena including double resonance peaks, biperiodic and quasi-periodic behaviors, and resonance hysteresis phenomenon are obtained, which are discussed in detail through diagrams for separated frequency responses with different frequency components and rotors’ orbits for different combinations of system parameters. Most prominently, for a relatively small unbalance of rotor as well as a relatively large clearance of the inter-shaft bearing, the resonance hysteresis phenomena are more obvious. The results obtained are also compared with the direct numerical simulation results, and the comparisons show good agreements. In addition, the methodology formulated in this paper is a general approach, which can be applied to other engineering systems with multi-frequency excitations.

Noble metal nanostructures for double plasmon resonance with tunable properties

We report and compare two vacuum-based strategies to produce Ag/Au materials characterized by double plasmon resonance peaks: magnetron sputtering and method based on the use of gas aggregation sources (GAS) of nanoparticles. It was observed that the double plasmon resonance peaks may be achieved by both of these methods and that the intensities of individual localized surface plasmon resonance peaks may be tuned by deposition conditions. However, in the case of sputter deposition it was necessary to introduce a separation dielectric interlayer in between individual Ag and Au nanoparticle films which was not the case of films prepared by GAS systems. The differences in the optical properties of sputter deposited bimetallic Ag/Au films and coatings consisted of individual Ag and Au nanoparticles produced by GAS is ascribed to the divers mechanisms of nanoparticles formation.

Magnetic Properties of Ferromagnetic Microstructured Multilayer Films

A series of microstructured FeNi/SiO2/FeCoSiB striped multilayers and FeNi/SiO2 /FeCoSiB continuous multilayers were fabricated on a Si(111) substrate by magnetron sputtering and ultraviolet photolithography. High-frequency permeability spectra have double resonance peaks, and the higher resonance peaks can be adjust from 2.5 GHz to 4.8 GHz. The results may be applied to new devices that require controlled, high-permeability resonance bands.

Study of magnetic properties and double resonance peaks of FeCoB/SiO 2 /FeCoSiB magnetic films

Abstract Soft-magnetic multilayers with or without SiO2 interlayer were fabricated on Si (111) substrates using magnetron sputtering. The static magnetic and high frequency electromagnetic properties of FeCoB(60 nm)/SiO2(6 nm)/FeCoSiB(t nm) or FeCoB(60 nm)/FeCoSiB(t nm)were systematically investigated. The experimental results showed that all multilayers had an in-plane uniaxial magnetic anisotropy and the interlayer of SiO2 could decouple the different magnetic phases leading to steps in hysteresis loops. Two resonance peaks of complex permeability spectra were observed for FeCoB(60 nm)/SiO2(6 nm)/FeCoSiB(t nm) films. The method to adjust the resonance frequency and FWHM is simple and robust, which may be potential for industrial application.

Spin orientation driven static and dynamic magnetic process in amorphous FeCoBSi thin films

The spin orientation dependence of magnetic hysteresis and microwave ferromagnetic resonance data are investigated in FeCoBSi amorphous thin films. Demagnetization effect allows the weak interface-rooted out-of-plane anisotropy to build up local spin orientation domains under the dominant in-plane anisotropy. As a result, two phase magnetization reversal and double-peak ferromagnetic resonance traces with varying damping behavior are observed. Due to the distribution of in-plane and out-of-plane spin orientations, the ferromagnetic resonance bandwidth has been extensively expanded with the full width at half maximum increased from 1.2 GHz to 3.5 GHz.

Magnetic properties and high frequency characteristics of FeCoAlON alloy films

In this work, we report the magnetic properties, domain structures and high frequency properties of FeCoAlON alloy films prepared by reactive magnetron sputtering. With increasing N addition content, the films transfer from in-plane anisotropic properties to isotropic behavior. The obvious stripe domain structure is observed in the films with high N content, and the domain parameters depend on the thickness of the films. The XRD analysis indicates that the stripe domain may origin from the stress-induced perpendicular anisotropy by Al, O and N addition. Meanwhile, a double-peak resonance behavior is observed in the permeability spectra of the films with stripe domain structure.

FDTD Modelling of Silver Nanoparticles Embedded in Phase Separation Interface of H‐PDLC

We report localized surface plasmon resonance (LSPR) of silver nanoparticles (NPs) embedded in interface of phase separation of holographic polymer‐dispersed liquid crystal (H‐PDLC) gratings using Finite‐Difference Time Domain method. We show that silver NPs exhibit double resonance peak at the interface, and these peaks are influenced by the angle of incident light. We observe a blue shift of the wavelength of resonance peak as the incident angle increases. However, the location of silver NPs at the interface has nearly no effect on the wavelength of resonance peak. Also we show near‐field and far‐field properties surrounding silver NPs and find that field distribution can be controlled through rotation of incident angle. Therefore, LSPR properties of silver NPs within H‐PDLC gratings can be excited by appropriate wavelength and angle of the incident light.

Stochastic resonance in the two-dimensional q-state clock models.

We numerically study stochastic resonance in the two-dimensional q-state clock models from q=2 to 7 under a weak oscillating magnetic field. As in the mean-field case, we observe double resonance peaks, but the detailed response strongly depends on the direction of the field modulation for q≥5 where the quasiliquid phase emerges. We explain this behavior in terms of free-energy landscapes on the two-dimensional magnetization plane.

Double magnetic resonance and spin anisotropy in Fe-based superconductors due to static and fluctuating antiferromagnetic orders

Motivated by recent neutron scattering experiments in Fe-based superconductors, we study how the magnetic resonance in the superconducting state is affected by the simultaneous presence of either static or fluctuating magnetic orders using the random phase approximation. We find that for the underdoped materials with coexisting superconducting and antiferromagnetic orders, spin rotational symmetry is explicitly broken at the ordering momentum $Q_1 = (\pi,0)$. Only the longitudinal susceptibility exhibits the resonance mode, whereas a spin-wave Goldstone mode develops in the transverse component. Meanwhile, at the frustrated momentum $Q_2 = (0,\pi)$, the susceptibility becomes isotropic in spin space and the magnetic resonance exists for both components. Furthermore, the resonance energies at $Q_1$ and $Q_2$ have distinct scales, which provides a natural explanation for the recently observed double resonance peaks. In addition, we show that near optimal doping the existence of strong magnetic fluctuations, which are modeled here via a Gaussian mode, can still induce the spin anisotropy in the magnetic susceptibility.

Tunability of LSPR using gold nano-particles embedded in a liquid crystal cell

Tunability of localized surface plasmon resonance (LSPR) of an ordered array of gold nano-particles is investigated in this paper. Herein, the array is embedded in a liquid crystal cell and then sandwiched with two glass substrates. The extinction spectra are computed using the Finite-Difference Time Domain (FDTD) method. The LSPR tunability of gold nanostructures is compromised by the anchoring effects of surrounding LC molecules, this effect can be compensated by optimizing geometric parameters of gold nanostructures. Interestingly, double resonant peaks are achieved with optimized structure. Meanwhile, the tunability of LSPR is improved up to 72nm with anchoring effects taken into account.

Polarization enhancement of microwave absorption by increasing aspect ratio of ellipsoidal nanorattles with Fe3O4 cores and hierarchical CuSiO3 shells.

The shape anisotropy of the nanostructured nanorattles is one of the key factors that affect their microwave absorption performance. In the present study, the microwave absorption performance of ellipsoidal Fe3O4@CuSiO3 nanorattles with different aspect ratios was investigated. Results demonstrated that the ellipsoidal nanorattles with the aspect ratio of 3-4 exhibited about 20% enhancement of microwave absorption intensity compared with spherical Fe3O4@CuSiO3. Generally, as the aspect ratio increased from 2.0 to 3.5, the microwave absorption peak was enhanced monotonously from -20 dB to -30 dB. It was found that the ellipsoidal nanorattles with larger aspect ratio exhibited higher coercivity and double resonance peaks of the real part of complex permittivity, resulting in the improvement of microwave absorption performance. Our research gives insights into the understanding of the anisotropic effect of nanorattles on microwave absorption performance.

Research on the Resonance Properties of E-Type Nano Antenna

Finite Difference Time Domain method(FDTD) is used to study the resonance properties of E-type nano antenna in this paper. According to the result of numerical simulation,the size and location of ledge part made a great influence on the resonance properties of holistic nano antenna while major rectangle part is invariant.The electronic field distribution, enhancement factor and corresponding resonance frequency of E-type nano antennas with invariant major rectangle part and different ledge parts are calculated through FDTD method,comparing with rectangle nano antenna without ledge part, E-type nano antenna has a great promotiom in electronic field enhancement at about 100 times of the excite electronic field intensity while regular rectangle nano antenna can achieve about 30times only.The resonance frequency is relate to the ledge part ,by changing the size and location of ledge part,resonant frequency can be adjusted between 340Thz and 400Thz,at the meantime, the field enhancement almost unchanged. After a glass substrate is added under the E-type nano antenna with constant size,the electronic field intensification factor improved significantly and the electronic field spread over the area around the ledge part rather than the junction of glass and metal.The horizontal position of ledge part has an effect on holistic resonance properties.When the ledge part located in the middle, the electronic field intensification factor of three ledge parts rised to 240 times at the same time,and distinct double resonance peak appeared.When the ledge part moved to the edge, the electronic field enhancement around the ledge parts on the sides weaken and middle ledge part rised to 350 times,double resonance peak disappeared.

Broadband Tunable and Double Dipole Surface Plasmon Resonance by TiO2 Core/Ag Shell Nanoparticles

A design of a TiO2 core and Ag shell spherical nanoparticle is theoretically presented. The nanoparticles display double dipole plasmonic resonance peaks: one located at the ultraviolet range, the other is widely tunable from the visible to the near infrared region. The tunability can be easily controlled by varying the sizes of the core and the shell. The near field patterns of the double plasmonic resonance peaks are analyzed, and the dipole resonance modes for those two peaks are confirmed for the suitable core–shell sizes.

Research on double resonance peaks and abnormal frequency shift in permeability spectra of annealed FeCoB films

A FeCoB magnetic film was prepared by a magnetron sputtering method and then was divided into several small pieces for vacuum annealing at different temperatures. The dependence of the coercivity along the hard axis on the annealing temperature reveals a degeneration of softness with the growth of grain size when the annealing temperature is above 350 °C. In permeability spectra measurements, double resonance peaks and an abnormal positive shift in the resonance peak at higher frequency with the increase in annealing temperature are observed. The existence of two peaks is attributed to the double magnetic phases (Fe and FeCo) in the films. The positive shift in the resonance peak at higher frequency has been analyzed and ascribed to the enhanced internal stray fields with the annealing temperature. This phenomenon of positive frequency-shift is very fascinating and novel, which makes the ferromagnetic films more efficient for the applications in the noise absorbing area.