Investigation of magnetization reversal process in pinned CoFeB thin film by in-situ Lorentz TEM

Exchange bias effect has been widely employed for various magnetic devices.The experimentally reported magnitude of exchange bias field is often smaller than that predicted theoretically,which is considered to be due to the partly pinned spins of ferromagnetic layer by antiferromagnetic layer.However,mapping the distribution of pinned spins is challenging.In this work,we directly image the reverse domain nucleation and domain wall movement process in the exchange biased Co Fe B/Ir Mn bilayers by Lorentz transmission electron microscopy.From the in-situ experiments,we obtain the distribution mapping of the pinning strength,showing that only 1/6 of the ferromagnetic layer at the interface is strongly pinned by the antiferromagnetic layer.Our results prove the existence of an inhomogeneous pinning effect in exchange bias systems.

Anomalously Strong Scattering of Spontaneously Produced Laser Radiation in the First Free-Electron Laser and Study of Free-Electron Two-Quantum Stark Lasing in an Electric Wiggler with Quantum-Wiggler Electrodynamics

We calculate the scattering cross section of an electron with respect to the spontaneously produced laser radiation in the first free-electron laser （FEL） with quantum-wiggler electrodynamics （QWD）. The cross section is 1016 times the Thomson cross section, confirming the result obtained by a previous analysis of the experimental data. A QWD calculation show that spontaneous emission in an FEL using only an electric wiggler can be very strong while amplification through net stimulated emission is practically negligible.

Strategy of preparing SmCo based films with high coercivity and remanence ratio achieved by temperature and chemical optimization

SmCo based films with excellent intrinsic magnetic properties have promising applications in micro-electro-mechanical system(MEMS).However,due to the complexity of phase composition and uncontrollable crystallization degree of SmCo hard magnetic phase in the film,both the coercivity(Hc)and remanence(Mr)of films are difficult to enhance simultaneously.In this paper,SmCo based films were deposited with a Cr underlayer and capping layer on single crystal Si substrates via magnetron sputtering process.The effects of annealing parameters and Sm/Co atomic ratio on the phase structure and coercivity of films are discussed.By adjusting the Sm/Co atomic ratio from 1:5 to 1:4,Co soft magnetic phase disappears and the single phase SmCo5 is obtained,leading to the increase of coercivity of the films from 30 to 34 kOe.The influence of deposition temperature and Cu doping on magnetic properties of SmCo based films was investigated.When the deposition temperature increases from room temperature to 250℃,the coercivity will further increase from 34 to 51 kOe.However,a severe kink is observed in the demagnetization curves due to the poor exchanged coupling.An analysis of transmission electron microscopy(TEM)confirms that the average size of non-hard magnetic amorphous phase exceeds the effective exchanged coupling length of SmCo5,which contributes to the decoupling and low remanence ratio.Therefore,doping Cu and applying a post-annealing process can significantly improve the crystallization degree of the films.Both the coercivity and the remanence ratio of the demagnetization curves are greatly enhanced.We propose a plausible strategy to prepare the SmCo based films with high coercivity and remanence ratio by temperature and chemical optimization,which can be utilized in high performed MEMS devices.

Effect of exchange coupling on magnetic property in Sm–Co/α-Fe layered system

The hysteresis loops as well as the spin distributions of Sm-Co/a-Fe bilayers have been investigated by both three- dimensional （3D） and one-dimensional （1D） micromagnetic calculations, focusing on the effect of the interface exchange coupling under various soft layer thicknesses ts. The exchange coupling coefficient Alas between the hard and soft ,layers varies from 1.8 x10-6 erg/cm to 0.45 x 10-6 erg/cm, while the soft layer thickness increases from 2 nm to 10 nm. As the exchange coupling decreases, the squareness of the loop gradually deteriorates, both pinning and coercive fields rise up monotonically, and the nucleation field goes down. On the other hand, an increment of the soft layer thickness leads to a significant drop of the nucleation field, the deterioration of the hysteresis loop squareness, and an increase of the remanence. The simulated loops based on the 3D and 1D methods are consistent with each other and in good agreement with the measured loops for Sm-Co/a-Fe multilayers.

Advanced strategies of scaffolds design for bone regeneration

Bone defects are encountered substantially in clinical practice,and bionic scaffolds represent a promising solution for repairing bone defects.However,it is difficult to fabricate scaffolds with bionic structures and reconstruct the microenvironment to fulfill the satisfying repair effects.In this review article,we first discuss various strategies for the design and construction of bionic scaffolds to promote bone defect repair,especially including the structural construction of the scaffold and the integration of bioactive substances together with the application of external stimuli.We then discuss the roles of artificial intelligence and medical imaging in aiding clinical treatment.Finally,we point out the challenges and future outlooks in developing multifunctional bone repair scaffolds,aiming to provide insights for improving bone regeneration efficacy and accelerating clinical translation.

Nighttime meridional neutral wind responses to SAPS simulated by the TIEGCM:A universal time effect

The present work uses the Thermosphere Ionosphere Electrodynamics General Circulation Model(TIEGCM),under geomagnetically disturbed conditions that are closely related to the southward interplanetary magnetic field(IMF),to investigate how the nighttime poleward wind(30°–50°magnetic latitude and 19–22 magnetic local time)responds to subauroral polarization streams(SAPS)that commence at different universal times(UTs).The SAPS effects on the poleward winds show a remarkable UT variation,with weaker magnitudes at 00 and 12 UT than at 06 and 18 UT.The strongest poleward wind emerges when SAPS commence at 06 UT,and the weakest poleward wind develops when SAPS occur at 00 UT.A diagnostic analysis of model results shows that the pressure gradient is more prominent for the developing of the poleward wind at 00 and 12 UT.Meanwhile,the effect of ion drag is important in the modulation of the poleward wind velocity at 06 and 18 UT.This is caused by the misalignment of the geomagnetic and geographic coordinate systems,resulting in a large component of ion drag in the geographically northward(southward)direction due to channel orientation of the SAPS at 06 and 18 UT(00 and 12 UT).The Coriolis force effect induced by westward winds maximizes(minimizes)when SAPS commence at 12 UT(00 UT).The centrifugal force due to the accelerated westward winds shows similar UT variations as the Coriolis force,but with an opposite effect.

Mathematical foundation of turbulence generation-From symmetric to asymmetric Liutex

Vortices have been regarded as the building blocks and muscles of turbulence for a long time. To better describe and analyze vortices or vortical structures, recently a new physical quantity called Liutex (previously named Rortex) is introduced to present the rigid rotation part of fluid motion (Liu et al. 2018). Since turbulence is closely related to the vortex, it can be postulated that there exists no turbulence without Liutex. According to direct numerical simulations (DNS) and experiments, forest of hairpin vortices has been found in transitional and low Reynolds number turbulent flows, while one-leg vortices are predominant in full developed turbulent flows. This paper demonstrates that the hairpin vortex is unstable. The hairpin vortex will be weakened or lose one leg by the shear and Liutex interaction, based on the Liutex definition and mathematical analysis without any physical assumptions. The asymmetry of the vortex is caused by the interaction of symmetric shear and symmetric Liutex since the smaller element of a pair of vorticity elements determines the rotational strength. For a 2-D fluid rotation, if a disturbance shear effects the larger element, the rotation strength will not be changed, but if the disturbance shear effects the smaller element, the rotation strength will be immediately changed due to the definition of the Liutex strength. For a rigid rotation, if the shearing part of the vorticity and Liutex present the same directions, e.g., clockwise, the Liutex strength will not be changed. If the shearing part of the vorticity and Liutex present different directions, e.g., one clockwise and another counterclockwise, the Liutex strength will be weakened.Consequently, the hairpin vortex could lose the symmetry and even deform to a one-leg vortex. The one-leg vortex cannot keep balance, and the chaotic motion and flow fluctuation are doomed. This is considered as the mathematical foundation of turbulence formation. The DNS results of boundary layer transition are used to justify this theory.

Preparation and Magnetic Properties of Anisotropic SmCo5/Co Composite Particles

Anisotropic SmCo5/Co nanocomposite powders have been prepared by electroless Co deposition on commercial SmCo5 powders with hydrazine as reducer. The Co particles are mainly in the range of 8–27 nm and form dense/continuous soft magnetic coatings on the surface of SmCo5 powders. Exchange coupling happened between the coated Co soft magnetic particles and the SmCo5 hard phase. As a result, SmCo5/Co nanocomposite powders with remanence of73.58 emu/g and energy product of 13.74 MGOe were obtained in the optimum condition, as compared with those of70.52 emu/g and 13.40 MGOe for uncoated SmCo5 powders. The effects of Co adding amount on Co particle size, coating morphology, and magnetic properties of SmCo5/Co products were investigated.

Comparisons of JOULE 1 rocket thermospheric wind observations in high latitudes with GITM simulations

4 Summary and conclusion The JOULE sounding rocket 1 experiment was carried out at Poker Flat Research Range in Alaska around 1200 UT on March 27th,2003 with two instrumented rockets and one chemical tracer rocket.From the released TMA trails,neutral wind measurements from approximately 85 to 160 km altitude showed a vertically propagating wave and a jet structure around 120 km altitude.Large shears appeared at the bottom side of the jet with Richardson numbers close to or smaller than the critical value of 0.25,which implies the possible existence of Kelvin-Helmholtz instabilities caused by the vertical shear in the fast flows.

基于双折射晶体的快拍穆勒矩阵成像测偏原理分析

针对传统穆勒矩阵成像测偏仪包含活动部件,需进行多次测量,容易产生测量误差,不能对运动目标或动态场景进行同时、实时测量等问题,提出了一种以改进型萨瓦偏光镜为核心分光器件的快拍Mueller矩阵成像测偏技术(MSP-SMMIP).它不含任何活动部件,能通过单次快拍测量获取目标强度图像和全部16个穆勒矩阵阵元图像.它主要由偏振态产生和偏振态分析两部分组成,偏振干涉条纹通过偏振态产生光路后定位于测试样品上,随后这些条纹通过空间载频将样品的Mueller矩阵分量编码,经偏振态分析光路成像于焦平面上.采用斯托克斯矢量-穆勒矩阵形式阐明了光场偏振态被MSP-SMMIP调制的过程,给出了其像面干涉图表达式,讨论了Mueller矩阵反演和系统定标的方法.基于CCD相机参数分析了系统的光学指标.通过数值模拟实验给出模拟测量结果,通过定性和定量评价测量结果表明该系统的可行性.MSP-SMMIP技术具有稳态、快拍、结构简洁、易定标、可同时实时获取目标强度图像和全部Mueller矩阵阵元图像的显著特点.

一种减少空间调制快拍成像测偏仪伪信息的方法

空间调制快拍成像测偏技术能将偏振信息编码到一幅干涉图中,通过一次测量同时获取目标全部斯托克斯参量.针对空间调制快拍成像测偏技术中,目标像的高频部分对偏振信息通道产生串扰,导致重构的偏振信息包含有伪信息和频域重构目标像的空间分辨率低等问题,提出一种消除伪信息和获取全分辨率目标像的方法.该方法通过对两次快拍测量获得的干涉图进行简单加减运算,便可获得探测目标清晰的纯图像和高信噪比的偏振分量干涉图.本文对该方法进行了详细的理论分析,并通过计算机仿真和搭建实验平台,验证了该方法的可行性.这为空间调制快拍成像测偏技术获取全分辨率目标像和高质量重构偏振信息提供了新思路.

Study of optical and dielectric properties of annealed ZnO nanoparticles in the terahertz regime

The frequency-dependent optical and dielectric properties of annealed ZnO nanoparticles in the range of 0.1 to 0.9 THz are studied by using terahertz time-domain spectroscopy(THz-TDS).The refractive index,power absorption and complex dielectric constants are obtained and the experimental results are well fit with a simple effective medium theory in conjunction with a pseudo-harmonic model.This study reveals that annealed ZnO nanoparticles exhibit the similar phonon response characteristics to the single ZnO crystal and other ZnO nanostructures,such as tetrapods and nanowires.

Image registration:Required for all ophthalmic imaging as demonstrated by optoretinography

1.Introduction Ophthalmology focuses on relating structural changes to function and disease.From biomicroscopy,ophthalmoscopy and fundus photography,to electroretinography and visual evoked potentials the clinical purpose is to objectively assess visual function.However,these techniques are macroscopic and only grossly related to visual acuity.With the development of optical coherence tomography(OCT)in vivo histological resolution of the retina has become routine.

Combination of disulfiram and Copper􀀀Cysteamine nanoparticles induces mitochondria damage and promotes apoptosis in endometrial cancer

Endometrial cancer(EC)stands as one of the most prevalent gynecological malignancies affecting women,with its incidence and disease-related mortality steadily on the rise.Disulfiram(DSF),an FDA-approved medication primarily used for treating alcohol addiction,has exhibited promising anti-tumor properties.Studies have revealed DSF’s capacity for enhanced anti-tumor activity,particularly when combined with copper.The novel Copper-Cysteamine(CuCy)compound,Cu_(3)Cl(SR)_(2)(R--CH_(2)CH_(2)NH_(2)),showcases photodynamic effects and demonstrates significant anti-tumor potential under various conditions,including exposure to ultraviolet light,X-ray,microwave,and ultrasound.This study delves into exploring the synergistic anti-tumor effects and underlying mechanisms by utilizing copper-cysteamine in conjunction with DSF against endometrial cancer.The investigation involved comprehensive analyses encompassing in vitro experiments utilizing Ishikawa cells,in vivo studies,and transcriptomic analyses.Remarkably,the combined administration of both compounds at a low dose of 0.5μM exhibited pronounced efficacy in impeding tumor growth,inhibiting blood vessel formation,and stimulating cell apoptosis.Notably,experiments involving transplanted tumors in nude mice vividly demonstrated the significant in vivo anti-tumor effects of this combination treatment.Detailed examination through transmission electron microscopy unveiled compelling evidence of mitochondrial damage,cellular swelling,and rupture,indicative of apoptotic changes in morphology due to the combined treatment.Moreover,transcriptomic analysis unveiled substantial downregulation of mitochondrial-related genes at the molecular level,coupled with a significant hindrance in the DNA repair pathway.These findings strongly suggest that the combined application of CuCy and DSF induces mitochondrial impairment in Ishikawa cells,thereby fostering apoptosis and ultimately yielding potent anti-tumor effects.

Air stable Fe nanostructures with high magnetization prepared by reductive annealing

Monodispersed Fe nanospindles and nanoparticles were successfully synthesized through environmentfriendly reductive annealing ？-Fe OOH nanorods. Effects of annealing temperature and reaction atmosphere on microstructure, phase, and magnetic property of Fe nanostructures were investigated.The as-obtained pure Fe nanoparticles with mean size of 45 nm had a high saturation magnetization up to 207 emu/g, close to that of bulk material（218 emu/g）, which exhibited high air stability. After exposing in air for 2 and 7 days, the as synthesized Fe nanoparticles still showed high magnetization of 182 and141 emu/g, respectively.

A novel direct reduction method to synthesize ordered Fe-Pt alloy nanoparticles

In this work, a direct green solid-phase reduction method for the fabrication of large yield of ordered phase Fe-Pt alloy nanoparticles was reported, in which inorganic salts were used as metal precursors and H_2-containing atmosphere was used as reducer. Utilizing this method, the composition and chemical ordered phase, such as L1_2-Fe_3 Pt, L1_2-FePt_3, and L1_0-FePt phases can be easily achieved by one step reaction. The synthesized nanoparticles have clean surface because no organic precursors, no organic solutions or organic surfactants/ligands were used. Their magnetic performance and the formation mechanism of Fe-Pt alloy nanoparticles were also investigated. This strategy can be applied to synthesize many other types of alloy nanoparticles with desired composition and necessary crystal structure, which can be used for a variety of practical applications, such as in magnetism and catalyst research fields.

Magnetic reversal and magnetic memory effect in melt-spun Pr_2Fe_(14)B/α-Fe nanocomposite ribbons

The influence of CoCr addition on the microstructure and magnetic properties was investigated in nanocomposite Pr2Fel4B/a-Fe alloys prepared by melt spinning. It was shown that the magnetic properties of Pr2Fel4B/ct-Fe nanocomposite were im- proved by an addition of 10 at.% CoCr, in particular, coercivity （Hc） from 4.9 up to 5.3 kOe, maximum energy product （（BH）max） from 10.6 up to 13.9 MGOe, and remanence （Mr） from 94.2 up to 98.4 emu/g. The field dependencies of the reversible and irreversible magnetization components were derived from the recoil loops. Combining with the initial magnetization curves, the results indi- cated that the pinning of domain walls at the grain boundaries dominated the magnetization reversal in Pr2Fe14B/ct-Fe nanocomposite alloys. The magnetic memory effect was studied by measuring the magnetic moment relaxation at a cycle negative magnetic field with time interval of 600 s. The exchange-spring magnets with magnetic memory effect have a high potential for high density magnetic recording.

Strong hopping induced Dzyaloshinskii–Moriya interaction and skyrmions in elemental cobalt

The Dzyaloshinskii–Moriya interaction(DMI)is well known to favor a chiral rotation of the magnetic moments,which accounts for the emergence of the skyrmions.The DMI is a combined effect of spin–orbit coupling with broken inversion symmetry in magnets.Most of the noncentrosymmetric magnetic materials that bear skyrmions involve nonmagnetic elements.This work shows that strong DMIs exist in elemental cobalt with a β-Mn-type metastable structure.The variation of DMI among different cobalt pairs largely follows the variation of hopping magnitude in which p electrons play an important role.Although the DMIs between different atomic pairs partly cancels with each other,the net interaction is sufficient to result in a left-handed Bloch-type spiral.Spin dynamics simulation shows that a critical magnetic field of 2.9 T stabilizes skyrmions at 0 K.