Effect Of Bias Field Research Articles

Improvement on Qm in high-power piezoelectric ceramics through [111]c texture engineering

Improving mechanical quality factor Qm is of great significance for high-power applications. Here, a new strategy of the [111]c texture engineering was proposed to enhance the performances of high-power piezoelectric ceramics. The 5 vol% BaTiO3 (BT) templates with the [111]c preferred orientation were introduced into matrix powders of 0.03 Pb(Mn1/3Nb2/3)O3–0.33Pb(Ni1/3Nb2/3)O3–0.28 PbZrO3–0.36PbTiO3 (28PZ(R)) to form the [111]c textured ceramics (28PZ(T)), possessing a texture degree of 74 %. The multiple of uniform density in EBSD increased from 0.63 in randomly oriented 28 PZ(R) to 6.63 in 28PZ(T). The good lattice matching between BT templates and textured grains was observed using high-resolution transmission electron microscopy, confirming the microscopic origin of the [111]c texture. The maximum phase angle θmax of 88.2° was quite near 90° in 28PZ(T), ensuring the optimal Qm value of 1275 and the great figure of merit of 255,000 pC/N. The increased Qm in [111]c texture ceramics was confirmed due to the reduced intrinsic polarization directions rather than the pinning effect of the internal bias field. Larger grain sizes with larger domains restrained the movement of domain walls in 28 PZ(T), which was also favorable to higher Qm. This work may provide a new promising route for further high-power applications.

Research on loss characteristic of soft magnetic composites under nonsinusoidal excitations with DC bias field

Choosing a suitable core loss model and accurately predicting energy loss are crucial in designing magnetic devices with high efficiency based on soft magnetic composites (SMCs). In this work, FeSiAl and FeSi SMCs with a uniform insulating layer were fabricated by a phosphating process. The effects of excitation waveform and DC bias field on core loss have been investigated in depth. The results show that different remagnetization rates of SMC under ideal sinusoidal and square waves result in different core losses at the same frequency and flux density. The improved general Steinmetz equation and the modified Steinmetz equation were shown to be suitable for calculating core loss under square excitation waves without DC bias field. When the DC bias field is applied, the core loss of FeSiAl and FeSi SMCs was found to increase significantly due to the magnetization state gradually approaching saturation. Interestingly, the variation tendency of core loss can be accurately predicted using the waveform coefficient Steinmetz equation under square excitation conditions with a DC bias environment. This work not only provides deep insights into core loss under different excitation waveforms and DC bias fields but also determines the application scope of different core loss models.

High-Frequency Magnetic Response of Arrays of Planar Fe65Co35 Nanodots: Effects of Bias Field and Thermal Fluctuations

High-Frequency Magnetic Response of Arrays of Planar Fe₆₅Co₃₅ Nanodots: Effects of Bias Field and Thermal Fluctuations

Tuning quantum pathway interference in two-color laser photoemission using DC bias

Coherent control of quantum systems depends on the manipulation of quantum interference through external fields. In this work, we investigate the effects of DC bias field on coherent control of quantum pathways in two-color laser photoemission using exact analytical solutions of the one-dimensional time dependent Schrödinger equation. Increasing DC bias lowers and narrows the surface potential barrier, shifting the dominant emission to lower order multiphoton photoemission, photo-assisted tunneling and then direct tunneling. Those lower order photon absorption processes result in fewer possible pathways, and therefore modulation of photoemission current can be suppressed as DC field increases. It is shown that a maximum modulation depth of 99.4% can be achieved for a gold emitter at local DC bias F 0 = 0.5 V nm−1, fundamental (800 nm) laser field F 1 = 2.6 V nm−1 and second harmonic laser field F 2 = 0.25 V nm−1 . For a given set of input parameters, the total photoemission consists of different k-photon processes, each of which has their own different multiple possible pathways and interference effects. However, the quantum pathways and their interference for the dominant k-photon process and for the total photoemission probability show the same trends. This study demonstrates strong flexibility in tuning two-color lasers induced photoemission using a DC bias and provides insights into coherent control schemes of general quantum systems.

Synthesis of FeNi@kaolin soft magnetic composites with adjustable magnetic properties under different DC bias fields

Constructing the high-quality insulating layer and verifying the effects of DC bias field on magnetic properties is crucial in optimizing magnetic components based on soft magnetic composites. In this paper, a novel APTES-involved insulation technique has been developed to successfully coat kaolin on FeNi particles. Additionally, magnetic properties can be effectively regulated by changing the dosage of kaolin. The results show that anti-magnetization capacity and resistivity are improved by increasing kaolin content. Loss separation model and magnetic field simulation were used to investigate how the coating layer and DC bias field influence core loss for FeNi@kaolin SMCs. It can be found that structural demagnetizing field and eddy current were believed to be the main determinants of core loss variation in ideal sinusoidal waves, while the degree of magnetization state away from saturation plays a leading role in core loss under larger DC bias fields. Therefore, FeNi SMCs insulated with 1 wt% and 7 wt% kaolin exhibit the lowest core loss at DC bias field of 0 Oe and above 100 Oe, respectively. This work not only provides an effective insulating technique, but also supplies deeper insights into optimizing SMC-based magnetic components under larger DC bias fields.

Optimization of temperature stability and sensitivity of the giant magnetoimpedance effect in meander shaped Co-based amorphous ribbon using DC-biased current for sensor application

The influence of DC-biased current (I DC) on the longitudinal giant magnetoimpedance (GMI) effect in Co-based amorphous ribbon with a meander structure, taken from room temperature to 120 °C, has been investigated. The results show that I DC increases the temperature stability of the impedance of amorphous ribbon at 20 MHz. By deriving the expression of the transverse permeability according to a magnetization rotation model, we attributed the improved temperature stability to the combined effect of temperature and bias field H DC generated by I DC on the transverse permeability. It is also shown that I DC not only effectively inhibits the weakening of the GMI ratio at high temperature, but also significantly improves the GMI sensitivity. This will help to achieve sensitive low magnetic field measurement under large temperature fluctuation.

A solar-blind photodetector with ultrahigh rectification ratio and photoresponsivity based on the MoTe2/Ta:β-Ga2O3 pn junction

High-performance solar-blind photodetectors have attracted increasing attention due to their important implications in military, medical, and industrial applications. Among a large number of wide-bandgap semiconductors, the quasi-two-dimensional β-Ga2O3 material is considered as a novel candidate for the solar-blind region (200–280 nm) owing to its suitable bandgap and superior optoelectronic properties. Herein, we report an outstanding solar-blind photodetector based on the MoTe2/Ta:β-Ga2O3 pn junction, which exhibits excellent optoelectrical properties with a superhigh rectification ratio ∼1.0 × 107, an ultrahigh responsivity (R ∼358.9 A/W), a large detectivity (D* ∼3.1 × 1012 Jones), an excellent external quantum efficiency (EQE ∼1.76 × 105%), a fast photoresponse (21.1/84.5 ms), and a high rejection ratio (∼1.1 × 103) under forward bias (1.5 V) and deep-ultraviolet (UV) illumination. These superior photoresponses result from the rapid separation of photoexcited electron-hole pairs driven by the synergistic effect of the forward bias and built-in electric field of the pn junction. Moreover, the MoTe2/Ta:β-Ga2O3 pn junction photodetector also demonstrates competitive optoelectronic characteristics in self-powered mode with an ultralow dark current of 8.5 fA and a fairly high R of 9.2 mA/W. As a result, this work provides an alternative solution for designing and fabricating high-performance solar-blind photodetectors with potential applications in UV imaging, environmental monitoring, and insecure communication.

Key performance of tunneling magnetoresistance sensing unit modulated by exchange bias of free layer

Optimizing sample structural parameters, magnetic field annealing, series-parallel bridge design, current thermal effect, and additional bias magnetic field are common methods used for controlling the tunneling magnetoresistance (TMR) magnetic sensing performance. By employing these methods, key performance parameters of TMR sensors such as sensitivity, noise resistance index, linearity, and linear magnetic field range can be optimized and improved. Changing the sample structural parameters, such as the pinning layer, free layer, and barrier layer materials and thickness of the TMR magnetic sensing unit, can change the exchange bias field and thus enhance the TMR magnetic sensing performance parameters. In this study, through micromagnetic simulation and experimental measurements, it is discovered that by modifying the exchange coupling in the free layer CoFeB/Ru/NiFe/IrMn, the exchange bias field magnitude of the TMR free layer can be modulated, leading to improved performance of the TMR magnetic sensing unit. As the IrMn pinning effect is gradually enhanced, the linear magnetic field range of the TMR magnetic sensing unit increases, but the magnetic field sensitivity decreases. It is further found that the linearity of the TMR magnetic sensor is optimal within a range of ±0.5 times the magnetic moment variation of the free layer (primarily the CoFeB layer). Through our work, the effect of exchange bias field (caused by the pinning IrMn of the free layer) on the magnetic sensing performance is verified in the TMR magnetic sensing unit. Our work demonstrates more possibilities for designing and optimizing TMR magnetic sensors, enriching the dimensions of magnetic sensing performance modulation.

Analysis of spin-orbit torque magnetic tunnel junction model without external magnetic field assistance based on antiferromagnetism

The effect of spin-orbit torque (SOT) provides a new method of implementing ultra-low power spintronic devices. The in-plane exchange bias (EB) field in antiferromagnetic material can effectively assist SOT magnetization switching. Meanwhile, the utilization of voltage-controlled magnetic anisotropy (VCMA) can effectively reduce the switching barrier. Taking advantage of the EB and VCMA effect, it is possible to realize SOT magnetic tunnel junctions without external field assistance. In this work, a spin-orbit torque magnetic tunnel junction model composed of antiferromagnetic/ferromagnetism/oxides without external magnetic field is developed by solving the modified Landau-Lifshitz-Gilbert (LLG) modular equation, and its magnetization dynamics is analyzed and studied. The effective fields in the model include the demagnetization field, thermal noise field, perpendicular magnetic anisotropy field with VCMA effect, and exchange bias field. Taking IrMn/CoFeB/MgO material system for example, the factors affecting the precession of magnetization are investigated, such as the effect of the exchange bias field, the VCMA effect and the mechanism of SOT field-like torque. Considering the practical applications, the effect of the deviation of the fabrication process of magnetic tunnel junctions is also analyzed. The simulation results demonstrate that the combined effect of <inline-formula><tex-math id="M5">\begin{document}$ {{\boldsymbol{H}}_{{\text{EB}}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M5.png"/></alternatives></inline-formula> with VCMA effect can greatly reduce the critical <i>I</i><sub>SOT</sub>, thus assisting and realizing the complete field-free magnetization reversal; the SOT field-like torque plays a dominant role in realizing the magnetization reversal, and by adjusting the ratio of the SOT field-like torque to the damping-like torque, field free switching can be realized in the device at the ps grade ; and the MTJ can realize effective switching when the deviation of oxide thickness <inline-formula><tex-math id="M6">\begin{document}$ {\gamma _{{\text{tf}}}} \leqslant 10{\text{%}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M6.png"/></alternatives></inline-formula> or the deviation of free layer thickness <inline-formula><tex-math id="M7">\begin{document}$ {\gamma _{{\text{tox}}}} \leqslant 13{\text{%}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M7.png"/></alternatives></inline-formula>. Spin-orbit torque devices based on the antiferromagnetic without external magnetic field will provide highly promising solutions for a new-generation ultra-low power, ultra-high speed, and ultra-high integration devices and circuits.

Micromagnetic study of the effect of Dzyaloshinskii-Moriya interaction on magnetization reversal in magnetic nanodots of different shape

Thorough understanding of magnetization reversal process in perpendicularly magnetized nanostructures of different shapes in the presence of anti-symmetric exchange interaction is crucial in designing energy efficient magnetic storage devices. Here, we investigate the effect of interfacial Dzyaloshinskii-Moriya interaction (IDMI) and in-plane bias field (µ0H) on the magnetization reversal mechanism in perpendicularly magnetized square, circular and triangular nanodot of side length (diameter) 128 nm and thickness 1 nm using micromagnetic simulation Mumax3. Our results indicate a monotonic reduction in the coercive field with increase in the strength of IDMI and the nucleation of the reversal is observed at the edge of the nanodot irrespective of the shape. Additionally, the application of bias field pins the nucleation centre at the far edge of the dots and further lowers the energy barrier for the magnetization reversal with the extent of lowering related to the symmetry of the shape. Detailed analysis of energy profile reveals that due to the lateral asymmetry of the triangular nanodot (large spin canting), the total energy value is smaller for it at small magnitude of D (≤2 mJ/m2) and µ0H (≤100 mT) thereby making it preferred for energy efficient magnetization reversal in comparison to other two shapes. However, at sufficiently large magnitude of D (>2 mJ/m2) and µ0H (>100 mT), due to the laterally symmetric sides of the square (small spin canting), remarkable reduction of the energy barrier for the magnetization reversal is noticed. These findings indicate that the effect of D and µ0H in lowering the energy barrier for the magnetization reversal is intricately related to the symmetry associated with the shape of the nanodots. We thus believe that these results provide useful insight into the role of the shape of the nanoelement in designing spintronics devices where energy efficient magnetization reversal is required.

A new effective bias field correction model with TGV regularization

Based on statistical inference, we propose a new bias field correction model with TGV regularization, which can remove the bias field more effectively. The proposed method takes full advantage of the MRI image feature and the bias field characteristic. The corrupted image can be restored more effectively by the proposed method. For convenience and efficiency of calculation, the splitting method and primal-dual method are employed to solve the proposed model. A number of experiments show the proposed method is more effective than some state-of-the-art methods.

Electric-field assisted ring-opening polymerization: On the kinetics and product properties of DGEBA/aniline model system

This work demonstrates the effect of a high dc bias field (up to 160 kV/cm) on the polyaddition reaction of the modeled epoxy resin system. Polymerization of bisphenol A diglycidyl ether (DGEBA) supported by high electric field results in obtaining epoxides with significantly increased molecular weight, which is seven-fold higher than the zero-field reference ( M n = 4.7 kg/mol). We also found a markedly reduced dispersity ( Ð = 1.52 at 0 kV/cm, Đ = 1.21 at 160 kV/cm). The molecular weight and dispersity of obtained polymers change almost linearly with the reaction time. By following polymerization kinetics in the real-time of the experiment, via dielectric spectroscopy, we observe slowing down the reaction progress at dc fields of E = 160 kV/cm, compared to the zero-field case, E = 0 kV/cm. The polymer materials obtained in the presence/absence of static electric fields exhibit distinctly different glass transition temperatures. Our study highlights a better control over the reaction and product properties attained by using only the magnitude of the applied field as the control variable. Thus, a high electric field could provide an alternative pathway in synthesizing and developing advanced polymer materials using simpler, “green”, less-expensive, and technologically demanding approaches.

Effect of strong bias fields on the dielectric response of Ba0.95Са0.05TiO3 ferroelectric ceramics

Dielectric response of calcium-doped ceramics Ba0.95Ca0.05TiO3 was studied at different temperatures under stepwise action of a constant bias field and different sample prehistory. The microstructure of polarized and depolarized samples was studied using atomic force microscopy and scanning electron microscopy. The reverse dependences of the permittivity were obtained after preliminary holding at a constant temperature in the ferroelectric phase and without it. It was found that prolonged sample exposure at constant temperature enhanced the appearance of anomalies in the behavior of the permittivity reverse dependences due to contribution of the defective structure of the material (domain walls pinning and depinning).

Zero-field magnetometry using hyperfine-biased nitrogen-vacancy centers near diamond surfaces

Shallow nitrogen-vacancy (NV) centers in diamond are promising for nanomagnetometry, for they can be placed proximate to targets. To study the intrinsic magnetic properties, zero-field magnetometry is desirable. However, for shallow NV centers under zero field, the strain near diamond surfaces would cause level anticrossing between the spin states, leading to clock transitions whose frequencies are insensitive to magnetic signals. Furthermore, the charge noises from the surfaces would induce extra spin decoherence and hence reduce the magnetic sensitivity. Here, we demonstrate that the relatively strong hyperfine coupling (130 MHz) from a first-shell $^{13}\mathrm{C}$ nuclear spin can provide an effective bias field to an NV center spin so that the clock-transition condition is broken and the charge noises are suppressed. The hyperfine bias enhances the dc magnetic sensitivity by a factor of 22 in our setup. With the charge noises suppressed by the strong hyperfine field, the ac magnetometry under zero field also reaches the limit set by decoherence due to the nuclear spin bath. In addition, the 130 MHz splitting of the NV center spin transitions allows relaxometry of magnetic noises simultaneously at two well-separated frequencies (\ensuremath{\sim}2.870 \ifmmode\pm\else\textpm\fi{} 0.065 GHz), providing (low-resolution) spectral information of high-frequency noises under zero field. The hyperfine-bias-enhanced zero-field magnetometry can be combined with dynamical decoupling to enhance single-molecule magnetic resonance spectroscopy and to improve the frequency resolution in nanoscale magnetic resonance imaging.

Effect of Internal Bias Field on Poling Behavior in Mn-Doped Pb(Mg 1/3 Nb 2/3 )O 3 -29 mol%PbTiO 3 Single Crystal

Effect of Internal Bias Field on Poling Behavior in Mn-Doped Pb(Mg 1/3 Nb 2/3 )O 3 -29 mol%PbTiO 3 Single Crystal

The effect of bias field on the dielectric response of Ba0.95Pb0.05TiO3+Со2О3

The nature of the dielectric response in ferroelectric ceramics Ba0.95Pb0.05TiO3+Со2О3 (BPTC) under the influence of a constant bias field EB in the phase transition region is studied. It is found that increasing the content of cobalt reduces the value of the temperature shift of the maximum permittivity when connecting EB to the sample.

Segmentation of MRI images to detect multiple sclerosis using non-parametric, non-uniform intensity normalization and support vector machine methods

Multiple sclerosis (MS) is an inflammatory, chronic, persistent, and destructive disease of the central nervous system whose cause is not yet known but can most likely be the result of a series of unknown environmental factors reacting with sensitive genes. MRI is a method of neuroimaging studies that results in better image contrast in soft tissue. Due to the unknown cause of MS and the lack of definitive treatment, early diagnosis of this disease is important. MRI image segmentation is used to identify MS plaques. MRI images have an image error that is often called non-uniform light intensity. There are several ways to correct non-uniform images. One of these methods is Nonparametric Non-uniform intensity Normalization (N3). This method sharpens the histogram. The aim of this study is to reduce the effect of bias field on the MRI image using N3 algorithm and pixels of MRI images clustered by k-means algorithm. The dimensionality of the data is reduced by Principal Component Analysis (PCA) algorithm and then the segmentation is done by Support Vector Machine (SVM) algorithm. Results show that using the proposed system could diagnose multiple sclerosis with an average accuracy of 93.28%.

Bias-Corrected Intuitionistic Fuzzy C-Means With Spatial Neighborhood Information Approach for Human Brain MRI Image Segmentation

Segmentationof MRI imagesin the presence of artifacts such as noise and bias field effect (BFE) is challenging. In this article, to handle both artifacts, we have formulated an intuitionistic fuzzy set (IFS) theory based bias-corrected intuitionistic fuzzy c-means with spatial neighborhood information (SNI) method for magnetic resonance imaging (MRI) image segmentation. We represent the image in terms of IFSs using two well-known intuitionistic fuzzy generation functions, namely Sugeno’s negation function (SNF) and Yager’s negation function (YNF). In this way, the proposed approach takes advantage of the IFS theory to address the uncertainty and vagueness present in data. The SNI term helps to retain the fine image details in the segmentation process, which is usually lost when smoothing is used. The BFE is modeled as a slow varying intensity field additive in nature with mean zero in IFS framework. The proposed approach estimates the bias field and produces a segmented image simultaneously. The segmentation performance of the proposed method is evaluated in terms of the Dice score, average segmentation accuracy (ASA), and index of variation. Further, the comparison of the proposed method with other similar state-of-the-art methods on two well-known publicly available Brain MRI datasets shows the significant improvements in segmentation performance in terms of ASA, Dice score, and index of variation. The proposed approach achieves 93% ASA in the presence of severe bias field and noise artifacts on BrainWeb simulated dataset, which outperformed the state-of-the-art methods.

Bandgap and Vibration Reduction of Laminated Galfenol Phononic Crystal With Shunt Circuit

It is of great significance to adjust bandgaps (BGs) of laminated Galfenol phononic crystal (PC) by using nonlinearity of Villari effect and shunt elements for effectively reducing vibration. Based on the modified constitutive equations, the effective elastic modulus, and transfer matrix method (TMM), a dynamic nonlinear model with tunable elastic modulus for the PC is established. Comparisons between the calculated and measured results show that the model can describe the changing laws of the Galfenol rod's effective elastic modulus with frequency and shunt capacitance, and can predict nonlinearity of the rod. The effects of stress and bias field on the attenuation constant peak and cutoff frequency of Bragg BGs (BBGs) are analyzed, and the optimal and suboptimal operating points of BBGs are determined. The effects of shunt capacitance and stress on BBGs, resonant BGs (RBGs), and common BGs (CBGs) are analyzed, and it is found that larger magnetomechanical coupled factor and smaller shunt capacitance can effectively reduce vibration.

Bias field correction for improved compressed sensing reconstruction in parallel magnetic resonance imaging

Parallel imaging and compressed sensing (PICS) may accelerate magnetic resonance imaging (MRI) acquisition with advanced reconstruction algorithms from under-sampled data set. However, bias field effects are often present in reconstructed MRI images due to hardware limitation and object property, which might lead to reconstruction imperfection with conventional PICS reconstruction due to altered image sparsity. In this paper, the MR signal bias field effects is modeled, and it was found that the bias field effects would induce reconstruction artifacts in the low-signal-intensity area. Then it was proposed to add a bias correction step into the PICS reconstruction framework to improve the reconstruction, and the proposed method was evaluated the proposed method via both simulation and in vivo study. It was then shown that the proposed method leads to improved image reconstruction in the low-signal-intensity area, with little extra computational effort needed compared to standard PICS reconstruction. This method could be readily extended to other signal processing area where the signal inhomogeneity problem is present and signal sparsity is exploited.