Interplay Between Vorticity and Chirality Inside the Vortex Core in Chiral p-Wave Superconductors

The vortex core in chiral p-wave superconductors exhibits various properties owing to the interplay between the vorticity and chirality inside the vortex core. In the chiral p-wave superconductors, the site-selective nuclear spin-lattice relaxation rate T ^–1 ₁ is theoretically studied inside the vortex core within the framework of the quasiclassical theory of superconductivity. T ^–1 ₁ at the vortex center depends on the sense of the chirality relative to the sense of the magnetic field. The effect of a tilt of the magnetic field upon T ^–1 ₁ is investigated. The effect of the anisotropy in the superconducting gap and the Fermi surface is then investigated. The result is expected to be experimentally observed as a sign of the chiral pairing state in a superconducting material Sr₂RuO₄.     

Chiromagnetic Plasmonic Nanoassemblies with Magnetic Field Modulated Chiral Activity

Chiral plasmonic nanoassemblies, which exhibit outstanding chiroptical activity in the visible or near‐infrared region, are popular candidates in molecular sensing, polarized nanophotonics, and biomedical applications. Their optical chirality can be modulated by manipulating chemical molecule stimuli or replacing the building blocks. However, instead of irreversible chemical or material changes, real‐time control of optical activity is desired for reversible and noninvasive physical regulating methods, which is a challenging research field. Here, the directionally and reversibly switching optical chirality of magneto‐plasmonic nanoassemblies is demonstrated by the application of an external magnetic field. The gold‐magnetic nanoparticles core–satellite (Au@Fe₃O₄) nanostructures exhibit chiral activity in the UV–visible range, and the circular dichroism signal is 12 times greater under the magnetic field. Significantly, the chiral signal can be reversed by regulating the direction of the applied magnetic field. The attained magnetic field‐regulated chirality is attributed to the large contributions of the magnetic dipole moments to polarization rotation. This magnetic field‐modulated optical activity may be pivotal for photonic devices, information communication, as well as chiral metamaterials.     

Magnetic and Electric Control of Circularly Polarized Emission through Tuning Chirality‐Generated Orbital Angular Momentum in Organic Helical Polymeric Nanofibers

Circularly polarized light emission promotes the development of smart photonic materials for advanced applications in chiral sensing and information storage. The orbital angular momentum is a unique property for organic chiral helical materials. In this work, a type of organic chiral polymeric nanowires is designed with strong chirality induced orbital angular momentum. Under the stimulus of an external magnetic field of 600 mT, circularly polarized emission from the chiral polymeric nanowire becomes more pronounced, where the g factor increases from 0.21 to 0.3. The observed phenomena mainly originate from the chirality‐dependent orbital angular momentum. Moreover, the orbital angular momentum in helical chiral nanowire structures can be suppressed by inhibiting electron transport in a helical way to diminish circularly polarized light emission at room temperature.     

轴向磁场下分离结晶熔体内热毛细对流的数值模拟

为研究轴向磁场对分离结晶Bridgman法生长CdZnTe晶体熔体热毛细对流的影响,采用有限差分法进行了三维数值模拟。结果表明轴向磁场能有效抑制熔体内的热毛细对流;轴向磁场对熔体内部温度分布也有较大的影响,能使等温线分布变得平缓;当磁场强度不变时,随着狭缝宽度的增大熔体内部的流动减弱。     

Irreversible change of surface impedance of high-Tc thin films due to D.C. magnetic field commutation

The magnetic field dependence of the surface impedance (resistance and reactance) of high-T _c thin films is found employing measurements of the quality factor and the frequency of the parallel plate resonator in a dc magnetic field up to 500 Oe at 10 GHz.c-Oriented YBa₂Cu₃O₇ thin films are examined. Enhancement of surface resistance and inductance with increase of magnetic field is observed. The effect of irreversible increase of surface impedance as compared to its initial values after a cycle of magnetic field commutation is found. A qualitative explanation of the observed effects based on the picture of magnetic vortex penetration and accumulation in the film due to strong pinning is presented.     

Effect of a pulsed magnetic field on the luminescence of silver chloride single crystals

The phenomenon of a long-term (tens of hours) increase in the intensity of photoluminescence of silver chloride single crystals upon a short-term (tens of seconds) action of a weak (～4 kOe) pulsed magnetic field has been observed for the first time. The observed effect is probably related to the disappearance of vacancy defect complexes present in the initial crystal, which exhibit decomposition via the magnon mechanism under the action of an applied pulsed magnetic field.     

Finite element analysis of combined heat and mass transfer in hydromagnetic micropolar flow along a stretching sheet

This paper presents a finite element solution of the problem of heat and mass transfer in a hydromagnetic flow of a micropolar fluid past a stretching sheet. The transformed equations for the flow regime are solved numerically by using finite element method. The effect of important parameters namely magnetic field parameter, material parameter, Eckert number and Schmidt number over velocity, microrotation, temperature and concentration functions has been studied. It has been observed that the magnetic field parameter has the effect of reducing the velocity and increasing the microrotation, temperature and concentration while the micropolar parameter has the opposite effect on these functions except temperature function. Temperature increases with the increase in Eckert number and concentration decreases with the increase in Schmidt number.     

Electric line source illumination of a chiral cylinder placed in another chiral background medium

An electric line source illumination of a chiral cylinder embedded in a chiral background medium is considered. The field expressions inside and outside of a chiral cylinder have been derived using the wave field decomposition approach. The effects of various chiral cylinders, chiral background media and source locations upon the scattering gain pattern have been investigated. It is observed that the chiral background reduces the backward scattering gain as compared to the free space background for a dielectric cylinder. It is also studied that by moving a line source away from a cylinder reduces the backward scattering gain for a chiral cylinder placed in a chiral background under some specific conditions. A unique phenomenon of reduced scattering gain has been observed at a specific observation angle for a chiral cylinder placed in a chiral background having an electric line source location of unity free space wavelength. An isotropic scattering gain pattern is observed for a chiral nihility background provided that if cylinder is chiral or chiral nihility type. It is also observed that this isotropic behaviour is independent of background and cylinder chirality.     

稀土Dy掺杂SrFe_(12)O_(19)永磁铁氧体的结构与性能

研究了掺杂稀土Dy对锶铁氧体制备工艺、结构与性能的影响关系。研究表明,取向磁场对铁氧体磁性能的影响十分显著:随着取向磁场强度的增加,锶铁氧体晶粒发生的晶面择优取向度也增大,剩磁Br、最大磁能积(BH)max和矫顽力Hc均有上升趋势。烧结温度的影响则较复杂:随着烧结温度的增加,剩磁Br和最大磁能积(BH)max均有上升趋势,而矫顽力Hc则呈下降之势。通过在Y30牌号SrFe12O19预烧料基础上掺杂0.2%Dy2O3,经700kA/m磁场、4414N/cm2压力湿法成型的样品在1230℃温度下烧结1h后的磁性能达到了Br=398mT、Hcj=254kA/m和(BH)max=29.1kJ/m3,它与不掺杂Dy2O3的样品相比分别提高了12mT、31kA/m和0.7kJ/m3。     

Single Domain 10 nm Ferromagnetism Imprinted on Superparamagnetic Nanoparticles Using Chiral Molecules

The rapid growth in demand for data and the emerging applications of Big Data require the increase of memory capacity. Magnetic memory devices are among the leading technologies for meeting this demand; however, they rely on the use of ferromagnets that creates size reduction limitations and poses complex materials requirements. Usually magnetic memory sizes are limited to 30–50 nm. Reducing the size even further, to the ≈10–20 nm scale, destabilizes the magnetization and its magnetic orientation becomes susceptible to thermal fluctuations and stray magnetic fields. In the present work, it is shown that 10 nm single domain ferromagnetism can be achieved. Using asymmetric adsorption of chiral molecules, superparamagnetic iron oxide nanoparticles become ferromagnetic with an average coercive field of ≈80 Oe. The asymmetric adsorption of molecules stabilizes the magnetization direction at room temperature and the orientation is found to depend on the handedness of the chiral molecules. These studies point to a novel method for the miniaturization of ferromagnets (down to ≈10 nm) using established synthetic protocols.     

Magnetoresistance of rolled-up Fe3Si nanomembranes

Magnetotransport of individual rolled-up Fe(3)Si nanomembranes is investigated in a broad temperature range from 4.2 K up to 300 K in pulsed magnetic fields up to 55?T. The observed magnetoresistance (MR) has the following pronounced features: (i) MR is negative in the investigated intervals of temperature and magnetic field; (ii) its magnitude increases linearly with the magnetic field in a low-field region and reveals a gradual trend to saturation when the magnetic field increases; (iii) the MR effect becomes more pronounced with increasing temperature. These dependences of MR on the magnetic field and temperature are in line with predictions of the spin-disorder model of the spin-flip s-d interaction assisted with creation or annihilation of magnons, which is expected above a certain critical temperature. Comparison of the MR features in rolled-up and planar samples reveals a substantial increase of the critical temperature in the rolled-up tube, which is attributed to a new geometry and internal strain arising in the rolled-up nanomembranes, influencing the electronic and magnetic properties of the material.     

MHD stagnation-point flow of an electrically conducting fluid on the surface of another quiescent fluid

An analysis is made of the orthogonal stagnation-point flow of an incompressible viscous electrically conducting fluid on the surface of another incompressible viscous electrically conducting quiescent fluid in the presence of a uniform magnetic field normal to the interface between the fluids. It is found that for small magnetic Reynolds number, the velocity at a point in the upper fluid increases and that at a point in the lower fluid decreases with increase in the magnetic field. It is also observed from the temperature distributions in the two given fluids that the interface temperature increases with increase in the magnetic field.     

AFM‐Based Spin‐Exchange Microscopy Using Chiral Molecules

Local magnetic imaging at nanoscale resolution is desirable for basic studies of magnetic materials and for magnetic logic and memories. However, such local imaging is hard to achieve by means of standard magnetic force microscopy. Other techniques require low temperatures, high vacuum, or strict limitations on the sample conditions. A simple and robust method is presented for locally resolved magnetic imaging based on short‐range spin‐exchange interactions that can be scaled down to atomic resolution. The presented method requires a conventional AFM tip functionalized with a chiral molecule. In proximity to the measured magnetic sample, charge redistribution in the chiral molecule leads to a transient spin state, caused by the chiral‐induced spin‐selectivity effect, followed by the exchange interaction with the imaged sample. While magnetic force microscopy imaging strongly depends on a large working distance, an accurate image is achieved using the molecular tip in proximity to the sample. The chiral molecules' spin‐exchange interaction is found to be 150 meV. Using the tip with the adsorbed chiral molecules, two oppositely magnetized samples are characterized, and a magnetic imaging is performed. This method is simple to perform at room temperature and does not require high‐vacuum conditions.     

退火工艺对铁基非晶薄带磁感应效应的影响

研究了频率、磁场强度以及退火工艺对Fe73.5Cu1Nb3Si13.5B9非晶薄带磁感应效应变化幅度的影响.研究结果表明:磁感应效应变化幅度随着磁场强度的增大而增大,随着频率的升高呈现先增大后减小的趋势;与淬火态非晶薄带相比,退火可以提高磁感应效应变化幅度,且经300℃×1h退火后的磁感应效应变化幅度最大.     

Measurements of the inhomogeneities of magnetic fields in a sector-type of slim electromagnet

A sector-type of slim electromagnet with iron pole pieces has been fabricated to obtain some precise information about the inhomogeneities of magnetic fields. Neither the eddy-current effect nor magnetic aftereffect, which are associated with the setting procedure and setting speed of the magnetic field, are observed in the present measurements. Sources producing field inhomogeneities along a central ray in the pole pieces with a sharp-cornered profile are the local saturation and hysteresis effect. The hysteresis effect is related to the magnetization-demagnetization process and is observed under a measuring precision better than 10^-4. The magnetic field distribution changes with the field strength independent of the magnetization-demagnetization process. Sources producing field inhomogeneities along a radial direction in the pole pieces with the sharp-cornered profile are the local saturation and the difference between leakage fluxes in pole-piece sides with the small and large curvature radii, which is due to the magnetic asymmetry of the pole-piece geometry along the radial direction. The B-constant design of pole pieces has excellent effects in avoiding field inhomogeneities due to the aforementioned sources, although the small cycling effect remains in field inhomogeneities along the central ray.     

Effect of transverse static magnetic field on radial microstructure of hypereutectic aluminum alloy during directional solidification

The effect of different scales thermoelectric magnetic convection(TEMC)on the radial solidification microstructure of hypereutectic Al alloy has been investigated under transverse static magnetic field during directional solidification,focusing on the formation of freckle.Our experimental and numerical simulation results indicate that the TEMC circulation at sample scale under transverse static magnetic field leads to the enrichment of solute Al on one side of the sample.The TEMC and the solute enrichment degree increase with the increase of magnetic field when the magnetic field increases to 0.5 T.The enrichment degree of solute elements under magnetic field is affected by temperature gradient and growth rate.The non-uniform distribution of solute Al in the radial direction of the sample results in the non-uniform distribution of primary dendrite arm spacing(PDAS).Moreover,the applied magnetic field can lead to freckle formation and its number increases with the increase of magnetic field.The change of freckle is consistent with the anisotropy TEMC caused by the anisotropy of primary dendrite or primary dendrite network under magnetic field.Finally,the mechanism of synergism effect of the anisotropy TEMC,the distribution of solute Al and the PDAS on freckle formation and evolution is studied during directional solidification under magnetic field.     

Induced Magnetic Anisotropy and Stress-Impedance Effect in Nanocrystalline$hboxFe_73.5hboxCu_1hboxNb_3hboxSi_13.5hboxB_9$Ribbons

The influence of direction and strength of induced magnetic anisotropy on stress-impedance (SI) effect was experimentally and theoretically studied in this paper. Experimentally, it was found that the magnetic anisotropy of the stress Joule heated$hboxFe_73.5hboxCu_1hboxNb_3hboxSi_13.5hboxB_9$nanocrystalline ribbons were determined by direction and strength of the induced anisotropy. Theoretical calculations of the direction and strength of the induced magnetic anisotropy suggest that transverse anisotropy and small anisotropic field result in an increase of the SI effect. To decrease the anisotropic field and increase the transverse anisotropy simultaneously, a complex annealing process was applied to$hboxFe_73.5hboxCu_1hboxNb_3hboxSi_13.5hboxB_9$ribbons, and it was found that the SI effect was drastically improved. A maximum change of 286% in the SI ratio of the complex annealed nanocrystalline$hboxFe_73.5hboxCu_1hboxNb_3hboxSi_13.5hboxB_9$ribbon was observed around 10 MHz frequencies.     

Magnetic alignment and patterning of cellulose fibers

The alignment and patterning of cellulose fibers under magnetic fields are reported. Static and rotating magnetic fields were used to align cellulose fibers with sizes ranging from millimeter to nanometer sizes. Cellulose fibers of the millimeter order, which were prepared for papermaking, and much smaller fibers with micrometer to nanometer sizes prepared by the acid hydrolysis of larger ones underwent magnetic alignment. Under a rotating field, a uniaxial alignment of fibers was achieved. The alignment was successfully fixed by the photopolymerization of a UV-curable resin precursor used as matrix. A monodomain chiral nematic film was prepared from an aqueous suspension of nanofibers. Using a field modulator inserted in a homogeneous magnetic field, simultaneous alignment and patterning were achieved.     

取向磁场强度对磁流变弹性体力磁性能的影响

为探究制备过程中取向磁场对MR E力磁性能的影响,制备了相同磁敏颗粒夹杂的两种不同基体特性的MR E,分别对其微观组织和材料的力学性能进行了系统研究.结果表明:随着取向磁场与硅油含量的增大,磁敏颗粒在MR E中的链状排布更加明显;所制备材料的磁致剪切模量与磁流变效应均随着取向磁场的增大而增大,并且其增加趋势随着硅油含量...     

Effect of steady magnetic field on laser-induced breakdown spectroscopy

Effects of a steady magnetic field on the laser-induced breakdown spectroscopy of certain elements (Mn, Mg, Cr, and Ti) in aqueous solution were studied, in which the plasma plume expanded across an external steady magnetic field (approximately 6 kilogauss). Nearly 1.6 times enhancement in the line emission intensity was observed in the presence of the magnetic field. The temporal evolution of the line emission showed a significant enhancement in plasma emission between 2- and 7- micro(s) gate delays for Mg in the presence of the magnetic field (5-30 micro(s) for Mn). This enhancement in the emission is attributed to an increase in the rate of recombination because of an increase in plasma density due to a magnetic confinement after cooling the plasma. The increase in the optical line emission due to magnetic confinement was absent when the plasma was hot with a dominant background (continuum) emission. The limits of detection of Mg and Mn were reduced by a factor of two in the presence of a steady magnetic field of 5 kilogauss.