We investigated the chiral magnetic effect(CME)in relativistic heavy-ion collisions through an improved two-plane method analysis of theΔγobservable,probing CP-symmetry breaking in the strong interactions and topolo...We investigated the chiral magnetic effect(CME)in relativistic heavy-ion collisions through an improved two-plane method analysis of theΔγobservable,probing CP-symmetry breaking in the strong interactions and topological properties of the QCD vacuum.Using a multiphase transport model with tunable CME strengths,we systematically compared the Au+Au and isobar collisions at√s_(NN)=200 GeV.We observed a reduced difference in the CME signal-to-background ratio between the spectator and participant planes for Au+Au collisions compared with isobar collisions.A comprehensive chi-square analysis across all three collision systems revealed stronger CME signatures in Au+Au collisions than in isobar collisions,particularly when measured with respect to the spectator plane.Our findings demonstrate the enhanced experimental reliability of the two-plane method for CME detection in Au+Au collisions.展开更多
The construction of carbon nanocoil(CNC)-based chiral-dielectric-magnetic trinity composites is considered as a promising approach to achieve excellent low-frequency microwave absorption.However,it is still challengin...The construction of carbon nanocoil(CNC)-based chiral-dielectric-magnetic trinity composites is considered as a promising approach to achieve excellent low-frequency microwave absorption.However,it is still challenging to further enhance the low frequency microwave absorption and elucidate the related loss mechanisms.Herein,the chiral CNCs are first synthesized on a threedimensional(3D)carbon foam and then combined with the FeNi/NiFe_(2)O_(4) nanoparticles to form a novel chiral-dielectric-magnetic trinity foam.The 3D porous CNC-carbon foam network provides excellent impedance matching and strong conduction loss.The formation of the FeNi-carbon interfaces induces interfacial polarization loss,which is confirmed by the density functional theory calculations.Further permeability analysis and the micromagnetic simulation indicate that the nanoscale chiral magnetic heterostructures achieve magnetic pinning and coupling effects,which enhance the magnetic anisotropy and magnetic loss capability.Owing to the synergistic effect between dielectricity,chirality,and magnetism,the trinity composite foam exhibits excellent microwave absorption performance with an ultrabroad effective absorption bandwidth(EAB)of 14 GHz and a minimum reflection of loss less than-50 dB.More importantly,the C-band EAB of the foam is extended to 4 GHz,achieving the full C-band coverage.This study provides further guidelines for the microstructure design of the chiral-dielectric-magnetic trinity composites to achieve broadband microwave absorption.展开更多
Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie te...Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie temperature and instability in air,it is hard to realize practical applications for the reported layered magnetic materials at present.In this paper,we developed a space-confined chemical vapor deposition method to synthesize ultrathin air-stable ε-Fe_(2)O_(3) nanosheets with Curie temperature above 350 K.The ε-Fe_(2)O_(3)/NbSe_(2) heterojunction was constructed to study the magnetic proximity effect on the superconductivity of the NbSe_(2) multilayer.The electrical transport results show that the subtle proximity effect can modulate the interfacial spin–orbit interaction while undegrading the superconducting critical parameters.Our work paves the way to construct 2D heterojunctions with ultrathin nonlayered materials and layered van der Waals(vdW)materials for exploring new physical phenomena.展开更多
High alumina slag will cause severe corrosion at the interface of alumina refractory,and the wetting behavior of slag is a key factor influencing the corrosion resistance of refractory ceramics.The static magnetic fie...High alumina slag will cause severe corrosion at the interface of alumina refractory,and the wetting behavior of slag is a key factor influencing the corrosion resistance of refractory ceramics.The static magnetic field is a promising solution for improvement in the slag resistance of refractory.The wetting of alumina refractory ceramics with different basicities of high alumina slags under a weak static magnetic field was analyzed,given that a weak static magnetic field can affect the corrosion behavior of refractory ceramics.Taking slag S_(3) as an example,when there was an external static magnetic field of 1.0 mT at 1600 ℃,the thickness of calcium aluminate reaction layer at the interface decreased by 36.7%,the denting depth of interface decreased by 35.6%,and the apparent wetting angle increased by 20%.The living radicals and their formation path in oxide melts were verified by first-principles calculation combined with electron paramagnetic resonance spectroscopy analysis.The influence of the flux density of a weak static magnetic field on the wetting behavior of slags was also explored.The contact angle of the slags increased owing to the inhibitory effect of magnetic field on the radicalinvolved reaction at the interface of the slag and the alumina refractory ceramic.The relationships between the magnetic flux density,diffusion coefficient,slag microstructure(hyperfine coupling constant),and contact angle were established.This provides a theoretical basis for the field control of radical involved reactive wetting between inorganic oxide slags and solid oxide ceramics.展开更多
Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes dev...Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.展开更多
Soil enzyme activities as affected by applied magnetic field were studied with three main soils (brown soil, black soil and albic soil) collected from Northeast China. Appropriate intensities of magnetic field could o...Soil enzyme activities as affected by applied magnetic field were studied with three main soils (brown soil, black soil and albic soil) collected from Northeast China. Appropriate intensities of magnetic field could obviously enhance the activities of hydrogen peroxidases, invertases, amylases and phosphatases in the three soils, although the effect varied with types and water regimes of the soils. Increasing times of magnetic treatment could multiple its good effect on the activities of hydrogen peroxidases in soils.展开更多
A study on the effect of applied magnetic field was performed with six types of soils collected fromnortheastern China. Magnetic field was found to cause changes of soil physicc-chemical properties and soilenzyme acti...A study on the effect of applied magnetic field was performed with six types of soils collected fromnortheastern China. Magnetic field was found to cause changes of soil physicc-chemical properties and soilenzyme activities. An appropriate applied magnetic field could cut down soil zeta-potential, soil specificsurface, soil water potential and soil swelling capacity; raise the charge density on soil colloids and theactivities of invertase, hydrogen peroxidase and amylase in the soils; enhance soil aggregation and improvesoil structural status and soil water-releasing capability.展开更多
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-F...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.展开更多
Based on the closed-orbit theory, the magnetic field effect in the photodetachment of negative ion in the electric field near a metal surface is studied for the first time. The results show that the magnetic field can...Based on the closed-orbit theory, the magnetic field effect in the photodetachment of negative ion in the electric field near a metal surface is studied for the first time. The results show that the magnetic field can produce a significant effect on the photodetachment of negative ion near a metal surface. Besides the closed orbits previously found by Duet al. for the H in the electric field near a metal surface （J. Phys. B 43 035002 （2010））, some additional closed orbits are produced due to the effect of magnetic field. For a given ion surface distance and an electric field strength, the cross section depends sensitively on the magnetic field strength. As the magnetic field strength is very small, its influence can be neglected. With the increase of the magnetic field strength, the number of the closed orbits increases greatly and the oscillation in the cross section becomes much more complex. Therefore we can control the photodetachment cross section of the negative ion by changing the magnetic field strength. We hope that our results may guide future experimental studies for the photodetachment process of negative ion in the presence of external fields and surfaces.展开更多
Fe43MsCra5Mo14C15B6Y2 （M = Mn, Co, Ni, and Cu in at.%） bulk metallic glasses （BMGs） are synthesized using the suction casting technique, and the glass-forming ability （GFA）, microstructure, and thermal and magne...Fe43MsCra5Mo14C15B6Y2 （M = Mn, Co, Ni, and Cu in at.%） bulk metallic glasses （BMGs） are synthesized using the suction casting technique, and the glass-forming ability （GFA）, microstructure, and thermal and magnetic properties of these glasses are extensively examined using X-ray diffraction, differential scanning calorimeter, and vibrating sample magnetometer techniques. Among the four BMG alloys, Fe43NisCr15Mo14C15B6Y2 exhibits the lowest coercivity and the highest saturation magnetization, Curie temperature, effective magnetic moment, and GFA. By contrast, Fe43MnsCrlsMo14C15B6Y2 presents the poorest magnetic properties, such as the highest coercivity and the lowest saturation magnetization, Curie temperature, and effective magnetic moment. Fe43Cu5Cr15MolaC15B6Y2 demonstrates the lowest thermal stability and GFA. The observed thermal, structural, and magnetic properties of these BMG alloys are discussed in terms of the kinetics of BMG synthesization and the formation of different ferromagnetic, ferrimagnetic, and antiferromagnetic phases.展开更多
Considering the actual magnetic field configuration in a Hall thruster, the effect of magnetic mirror on the radial profile of near-wall conductivity （NWC） is studied in this paper. The plasma electron dynamic proce...Considering the actual magnetic field configuration in a Hall thruster, the effect of magnetic mirror on the radial profile of near-wall conductivity （NWC） is studied in this paper. The plasma electron dynamic process is described by the test particle method. The Monte Carlo scheme is used to solve this model. The radial profile of electron mobility is obtained and the role of magnetic mirror in NWC is analysed both theoretically and numerically. The numerical results show that the electron mobility peak due to NWC is inversely proportional to the magnetic mirror ratio and the asymmetry of electron mobility along the radial direction gets greater when the magnetic mirror is considered. This effect indicates that apart from the disparity in the magnetic field strength, the difference in the magnetic mirror ratio near the inner and outer walls would actually augment the asymmetry of the radial profile of NWC in Hall thrusters.展开更多
In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12...In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.展开更多
Two-dimensional(2D)magnetic materials have aroused tremendous interest due to the 2D confinement of magnetism and potential applications in spintronic and valleytronic devices.However,most of the currently 2D magnetic...Two-dimensional(2D)magnetic materials have aroused tremendous interest due to the 2D confinement of magnetism and potential applications in spintronic and valleytronic devices.However,most of the currently 2D magnetic materials are achieved by the exfoliation from their bulks,of which the thickness and domain size are difficult to control,limiting the practical device applications.Here,we demonstrate the realization of thickness-tunable rhombohedral Cr_(2)Se_(3)nanosheets on different substrates via the chemical vapor deposition route.The magnetic transition temperature at about 75 K is observed.Furthermore,van der Waals heterostructures consisting of Cr_(2)Se_(3)nanosheets and monolayer WS2 are constructed.We observe the magnetic proximity effect in the heterostructures,which manifests the manipulation of the valley polarization in monolayer WS2.Our work contributes to the vapor growth and applications of 2D magnetic materials.展开更多
Numerical results show that an external magnetic field may influence significantly the flow pattern in the molten semiconductor of Czochralski crystal growth. The melt flow could be pronouncedly damped by a magnet. ic...Numerical results show that an external magnetic field may influence significantly the flow pattern in the molten semiconductor of Czochralski crystal growth. The melt flow could be pronouncedly damped by a magnet. ic field with the intensity of several thousands Gauss, while the temperature field is affected only in a less extent by the magnetic field.展开更多
The magnetic field effects （MFEs） are studied on photocatalytic degradation of methylene blue （MB） solution using ZnO and TiO2 particles. The UV-VIS-NIR spectrometer is used to monitor the MB concentrations, and t...The magnetic field effects （MFEs） are studied on photocatalytic degradation of methylene blue （MB） solution using ZnO and TiO2 particles. The UV-VIS-NIR spectrometer is used to monitor the MB concentrations, and the dependence of the reaction rate on the initial dye concentration and settling duration is studied under UV light irradiation. It is found that the MFEs exist on the heterogeneous reaction systems for both ZnO and TiO2 powders and that the extraordinary phenomenon is reproducible. For ZnO powder, the results are in good agreement with the second-order reaction kinetics following the Langmuir-Hinshelwood （L-H） model, while the reaction for TiO2 follows first-order kinetics. It enhances the photodegradation for ZnO, while it reduces or enhances the reaction for TiO2 depending on the initial dye concentrations. The MFEs become small or negligible when the same photodecomposition experiment is carried out after settling the MB solution for more than three hours for both ZnO and TiO2. It is suggested that the key factors of MFEs on photocatalytic degradation is the condition of the MB solution as well as the characteristics of photocatalysts. The alteration of the MFEs ascribed to the solution condition caused by variation of the settling time.展开更多
Magnetic radiation phenomena appear inevitably in the magnetic-resonance wireless power transfer （MR-WPT） system, and regarding this problem the magnetic-shielding scheme is applied to improve the electromagnetic pe...Magnetic radiation phenomena appear inevitably in the magnetic-resonance wireless power transfer （MR-WPT） system, and regarding this problem the magnetic-shielding scheme is applied to improve the electromagnetic performance in engineering. In this study, the shielding effectiveness of a two-coil MR-WPT system for different material shields is analyzed in theory using Moser＇s formula and Schelkunoff＇s formula. On this basis a candidate magnetic-shielding scheme with a double-layer structure is determined, which has better shielding effectiveness and coils coupling coefficient. Finally, some finite element simulation results validate the correctness of the theoretical analysis, and the shielding effectiveness with the double-layer shield in maximum is 30？dB larger than the one with the single-layer case.展开更多
The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a sup...The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.展开更多
The μi-T curves of the alloy Fe73.5Cu1 Nb3Si13.5B9 in the amorphous state and in the nanocrys-talline state have been investigated. For comparison, μi-T curves of the other two kinds of typical soft magnetic alloys ...The μi-T curves of the alloy Fe73.5Cu1 Nb3Si13.5B9 in the amorphous state and in the nanocrys-talline state have been investigated. For comparison, μi-T curves of the other two kinds of typical soft magnetic alloys also have been measured. It was found that a sharp Hopkinson peak appeared at the Curie point for each amorphous and crystalline alloy but there was no Hopkinson peak for the nanocrystalline alloy at the Curie point of the residual amorphous phase. This phenomenon has been explained in terms of the characteristic temperature dependence of the effective magnetic anisotropy.展开更多
Recent progresses in magnetic tunnel junctions with perpendicular magnetic anisotropy （PMA） are reviewed and summarized. At first, the concept and source of perpendicular magnetic anisotropy （PMA） are introduced. ...Recent progresses in magnetic tunnel junctions with perpendicular magnetic anisotropy （PMA） are reviewed and summarized. At first, the concept and source of perpendicular magnetic anisotropy （PMA） are introduced. Next, a historical overview of PMA materials as magnetic electrodes, such as the RE-TM alloys TbFeCo and GdFeCo, novel tetragonal manganese alloys Mn-Ga, L10-ordered （Co, Fe）/Pt alloy, multilayer film [Co, Fe, CoFe/Pt, Pd, Ni, AU]N, and ultra-thin magnetic metal/oxidized barrier is offered. The other part of the article focuses on the optimization and fabrication of CoFeB/MgO/CoFeB p-MTJs, which is thought to have high potential to meet the main demands for non-volatile magnetic random access memory.展开更多
The doping effects on the frustration and the magnetic properties in hexagonal compounds ot YMn0.9A0.1O3 （A=A1, Fe and Cu） are investigated. Experimental results indicate that both the non-magnetic and magnetic ion ...The doping effects on the frustration and the magnetic properties in hexagonal compounds ot YMn0.9A0.1O3 （A=A1, Fe and Cu） are investigated. Experimental results indicate that both the non-magnetic and magnetic ion dopants lead to the increase of magnetic moments and the decrease of the absolute value of Curie-Weiss temperature （｜θcw｜）- Compared with pure YMnOa, the geometrical frustration of YMn0.9 A0. 1O3 is greatly suppressed and the magnetic coupling in that exhibits dopant-dependent. In addition, for the doped YMno.gAo.103, the antiferromagnetic transition temperature （TN） is also suppressed slightly, which shows an abnormal dilution effect and it may be ascribed to the reduction of frustration due to the chemical substitution.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFA1604900)the National Natural Science Foundation of China(Nos.12147101,12325507,and 12105054)the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008)。
文摘We investigated the chiral magnetic effect(CME)in relativistic heavy-ion collisions through an improved two-plane method analysis of theΔγobservable,probing CP-symmetry breaking in the strong interactions and topological properties of the QCD vacuum.Using a multiphase transport model with tunable CME strengths,we systematically compared the Au+Au and isobar collisions at√s_(NN)=200 GeV.We observed a reduced difference in the CME signal-to-background ratio between the spectator and participant planes for Au+Au collisions compared with isobar collisions.A comprehensive chi-square analysis across all three collision systems revealed stronger CME signatures in Au+Au collisions than in isobar collisions,particularly when measured with respect to the spectator plane.Our findings demonstrate the enhanced experimental reliability of the two-plane method for CME detection in Au+Au collisions.
基金supported by the National Natural Science Foundation of China[Grant Nos.52272288 and 51972039]the China Postdoctoral Science Foundation[No.2021M700658].
文摘The construction of carbon nanocoil(CNC)-based chiral-dielectric-magnetic trinity composites is considered as a promising approach to achieve excellent low-frequency microwave absorption.However,it is still challenging to further enhance the low frequency microwave absorption and elucidate the related loss mechanisms.Herein,the chiral CNCs are first synthesized on a threedimensional(3D)carbon foam and then combined with the FeNi/NiFe_(2)O_(4) nanoparticles to form a novel chiral-dielectric-magnetic trinity foam.The 3D porous CNC-carbon foam network provides excellent impedance matching and strong conduction loss.The formation of the FeNi-carbon interfaces induces interfacial polarization loss,which is confirmed by the density functional theory calculations.Further permeability analysis and the micromagnetic simulation indicate that the nanoscale chiral magnetic heterostructures achieve magnetic pinning and coupling effects,which enhance the magnetic anisotropy and magnetic loss capability.Owing to the synergistic effect between dielectricity,chirality,and magnetism,the trinity composite foam exhibits excellent microwave absorption performance with an ultrabroad effective absorption bandwidth(EAB)of 14 GHz and a minimum reflection of loss less than-50 dB.More importantly,the C-band EAB of the foam is extended to 4 GHz,achieving the full C-band coverage.This study provides further guidelines for the microstructure design of the chiral-dielectric-magnetic trinity composites to achieve broadband microwave absorption.
基金The work is supported by the National Key Research and Development Program of China(Grant No.2022YFA1204104)the National Natural Science Foundation of China(Grant No.61888102)the Chinese Academy of Sciences(Grant Nos.ZDBS-SSW-WHC001 and XDB33030100).
文摘Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie temperature and instability in air,it is hard to realize practical applications for the reported layered magnetic materials at present.In this paper,we developed a space-confined chemical vapor deposition method to synthesize ultrathin air-stable ε-Fe_(2)O_(3) nanosheets with Curie temperature above 350 K.The ε-Fe_(2)O_(3)/NbSe_(2) heterojunction was constructed to study the magnetic proximity effect on the superconductivity of the NbSe_(2) multilayer.The electrical transport results show that the subtle proximity effect can modulate the interfacial spin–orbit interaction while undegrading the superconducting critical parameters.Our work paves the way to construct 2D heterojunctions with ultrathin nonlayered materials and layered van der Waals(vdW)materials for exploring new physical phenomena.
基金supported by the National Natural Science Foundation of China(52272022)Key Program of the Natural Science Foundation of Hubei Province of China(2021CFA071).
文摘High alumina slag will cause severe corrosion at the interface of alumina refractory,and the wetting behavior of slag is a key factor influencing the corrosion resistance of refractory ceramics.The static magnetic field is a promising solution for improvement in the slag resistance of refractory.The wetting of alumina refractory ceramics with different basicities of high alumina slags under a weak static magnetic field was analyzed,given that a weak static magnetic field can affect the corrosion behavior of refractory ceramics.Taking slag S_(3) as an example,when there was an external static magnetic field of 1.0 mT at 1600 ℃,the thickness of calcium aluminate reaction layer at the interface decreased by 36.7%,the denting depth of interface decreased by 35.6%,and the apparent wetting angle increased by 20%.The living radicals and their formation path in oxide melts were verified by first-principles calculation combined with electron paramagnetic resonance spectroscopy analysis.The influence of the flux density of a weak static magnetic field on the wetting behavior of slags was also explored.The contact angle of the slags increased owing to the inhibitory effect of magnetic field on the radicalinvolved reaction at the interface of the slag and the alumina refractory ceramic.The relationships between the magnetic flux density,diffusion coefficient,slag microstructure(hyperfine coupling constant),and contact angle were established.This provides a theoretical basis for the field control of radical involved reactive wetting between inorganic oxide slags and solid oxide ceramics.
基金supported by the Large Research Infrastructures China initiative Accelerator Driven System(No.2017-000052-75-01-000590)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022422)+1 种基金the Young Scientists of National Natural Science Foundation of China(No.12005275)the Advanced Energy Science and Technology Guangdong Laboratory(No.HND22PTZZYY)。
文摘Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.
文摘Soil enzyme activities as affected by applied magnetic field were studied with three main soils (brown soil, black soil and albic soil) collected from Northeast China. Appropriate intensities of magnetic field could obviously enhance the activities of hydrogen peroxidases, invertases, amylases and phosphatases in the three soils, although the effect varied with types and water regimes of the soils. Increasing times of magnetic treatment could multiple its good effect on the activities of hydrogen peroxidases in soils.
文摘A study on the effect of applied magnetic field was performed with six types of soils collected fromnortheastern China. Magnetic field was found to cause changes of soil physicc-chemical properties and soilenzyme activities. An appropriate applied magnetic field could cut down soil zeta-potential, soil specificsurface, soil water potential and soil swelling capacity; raise the charge density on soil colloids and theactivities of invertase, hydrogen peroxidase and amylase in the soils; enhance soil aggregation and improvesoil structural status and soil water-releasing capability.
基金supported by the National Natural Science Foundation of China(5080104350971080+2 种基金11174183)Natural Science Foundation of Shandong Province of China(JQ201201ZR2013AM020)
文摘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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074104 and 10604045)the University Science and Technology Planning Program of Shandong Province of China (Grant No. J09LA02)
文摘Based on the closed-orbit theory, the magnetic field effect in the photodetachment of negative ion in the electric field near a metal surface is studied for the first time. The results show that the magnetic field can produce a significant effect on the photodetachment of negative ion near a metal surface. Besides the closed orbits previously found by Duet al. for the H in the electric field near a metal surface （J. Phys. B 43 035002 （2010））, some additional closed orbits are produced due to the effect of magnetic field. For a given ion surface distance and an electric field strength, the cross section depends sensitively on the magnetic field strength. As the magnetic field strength is very small, its influence can be neglected. With the increase of the magnetic field strength, the number of the closed orbits increases greatly and the oscillation in the cross section becomes much more complex. Therefore we can control the photodetachment cross section of the negative ion by changing the magnetic field strength. We hope that our results may guide future experimental studies for the photodetachment process of negative ion in the presence of external fields and surfaces.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51274151 and 51371127)Shanghai Natural Science Foundation (Grant No. 13ZR1462400)
文摘Fe43MsCra5Mo14C15B6Y2 （M = Mn, Co, Ni, and Cu in at.%） bulk metallic glasses （BMGs） are synthesized using the suction casting technique, and the glass-forming ability （GFA）, microstructure, and thermal and magnetic properties of these glasses are extensively examined using X-ray diffraction, differential scanning calorimeter, and vibrating sample magnetometer techniques. Among the four BMG alloys, Fe43NisCr15Mo14C15B6Y2 exhibits the lowest coercivity and the highest saturation magnetization, Curie temperature, effective magnetic moment, and GFA. By contrast, Fe43MnsCrlsMo14C15B6Y2 presents the poorest magnetic properties, such as the highest coercivity and the lowest saturation magnetization, Curie temperature, and effective magnetic moment. Fe43Cu5Cr15MolaC15B6Y2 demonstrates the lowest thermal stability and GFA. The observed thermal, structural, and magnetic properties of these BMG alloys are discussed in terms of the kinetics of BMG synthesization and the formation of different ferromagnetic, ferrimagnetic, and antiferromagnetic phases.
基金supported by Changjiang Scholars and Innovative Research Team in University of China (PCSIRT)(No.IRT0520)National Natural Science Foundation of China (No.60671012)
文摘Considering the actual magnetic field configuration in a Hall thruster, the effect of magnetic mirror on the radial profile of near-wall conductivity （NWC） is studied in this paper. The plasma electron dynamic process is described by the test particle method. The Monte Carlo scheme is used to solve this model. The radial profile of electron mobility is obtained and the role of magnetic mirror in NWC is analysed both theoretically and numerically. The numerical results show that the electron mobility peak due to NWC is inversely proportional to the magnetic mirror ratio and the asymmetry of electron mobility along the radial direction gets greater when the magnetic mirror is considered. This effect indicates that apart from the disparity in the magnetic field strength, the difference in the magnetic mirror ratio near the inner and outer walls would actually augment the asymmetry of the radial profile of NWC in Hall thrusters.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274357,51501005,51590880,and 11674008)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-15-010A1)+1 种基金the China Postdoctoral Science Foundation(Grant No.2016M591071)the Key Research Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)
文摘In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52022029,91850116,51772084,62090035,and U19A2090)Hunan Provincial Natural Science Foundation of China(Grant Nos.2018RS3051 and 2018WK4004)the Key Program of the Hunan Provincial Science and Technology Department(Grant No.2019XK2001).
文摘Two-dimensional(2D)magnetic materials have aroused tremendous interest due to the 2D confinement of magnetism and potential applications in spintronic and valleytronic devices.However,most of the currently 2D magnetic materials are achieved by the exfoliation from their bulks,of which the thickness and domain size are difficult to control,limiting the practical device applications.Here,we demonstrate the realization of thickness-tunable rhombohedral Cr_(2)Se_(3)nanosheets on different substrates via the chemical vapor deposition route.The magnetic transition temperature at about 75 K is observed.Furthermore,van der Waals heterostructures consisting of Cr_(2)Se_(3)nanosheets and monolayer WS2 are constructed.We observe the magnetic proximity effect in the heterostructures,which manifests the manipulation of the valley polarization in monolayer WS2.Our work contributes to the vapor growth and applications of 2D magnetic materials.
基金supported by the National Natural Foundation of China
文摘Numerical results show that an external magnetic field may influence significantly the flow pattern in the molten semiconductor of Czochralski crystal growth. The melt flow could be pronouncedly damped by a magnet. ic field with the intensity of several thousands Gauss, while the temperature field is affected only in a less extent by the magnetic field.
文摘The magnetic field effects （MFEs） are studied on photocatalytic degradation of methylene blue （MB） solution using ZnO and TiO2 particles. The UV-VIS-NIR spectrometer is used to monitor the MB concentrations, and the dependence of the reaction rate on the initial dye concentration and settling duration is studied under UV light irradiation. It is found that the MFEs exist on the heterogeneous reaction systems for both ZnO and TiO2 powders and that the extraordinary phenomenon is reproducible. For ZnO powder, the results are in good agreement with the second-order reaction kinetics following the Langmuir-Hinshelwood （L-H） model, while the reaction for TiO2 follows first-order kinetics. It enhances the photodegradation for ZnO, while it reduces or enhances the reaction for TiO2 depending on the initial dye concentrations. The MFEs become small or negligible when the same photodecomposition experiment is carried out after settling the MB solution for more than three hours for both ZnO and TiO2. It is suggested that the key factors of MFEs on photocatalytic degradation is the condition of the MB solution as well as the characteristics of photocatalysts. The alteration of the MFEs ascribed to the solution condition caused by variation of the settling time.
基金Supported by the National Natural Science Foundation of China under Grant No 51377185
文摘Magnetic radiation phenomena appear inevitably in the magnetic-resonance wireless power transfer （MR-WPT） system, and regarding this problem the magnetic-shielding scheme is applied to improve the electromagnetic performance in engineering. In this study, the shielding effectiveness of a two-coil MR-WPT system for different material shields is analyzed in theory using Moser＇s formula and Schelkunoff＇s formula. On this basis a candidate magnetic-shielding scheme with a double-layer structure is determined, which has better shielding effectiveness and coils coupling coefficient. Finally, some finite element simulation results validate the correctness of the theoretical analysis, and the shielding effectiveness with the double-layer shield in maximum is 30？dB larger than the one with the single-layer case.
基金Project supported by the Science and Technology Development Fund of Higher Education of Tianjin,China(20130301)the Tianjin Research Program of Application Foundation and Advanced Technology,China(14JCQNJC4000)the National Natural Science Foundation of China(11604242)
文摘The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.
基金National Natural Science Foundation of China! under grant No. 59871013.
文摘The μi-T curves of the alloy Fe73.5Cu1 Nb3Si13.5B9 in the amorphous state and in the nanocrys-talline state have been investigated. For comparison, μi-T curves of the other two kinds of typical soft magnetic alloys also have been measured. It was found that a sharp Hopkinson peak appeared at the Curie point for each amorphous and crystalline alloy but there was no Hopkinson peak for the nanocrystalline alloy at the Curie point of the residual amorphous phase. This phenomenon has been explained in terms of the characteristic temperature dependence of the effective magnetic anisotropy.
基金supported by the State Key Project of Fundamental Research of Ministry of Science and Technology,China(Grant No.2010CB934400)the National Natural Science Foundation of China(Grant Nos.51229101 and 11374351)
文摘Recent progresses in magnetic tunnel junctions with perpendicular magnetic anisotropy （PMA） are reviewed and summarized. At first, the concept and source of perpendicular magnetic anisotropy （PMA） are introduced. Next, a historical overview of PMA materials as magnetic electrodes, such as the RE-TM alloys TbFeCo and GdFeCo, novel tetragonal manganese alloys Mn-Ga, L10-ordered （Co, Fe）/Pt alloy, multilayer film [Co, Fe, CoFe/Pt, Pd, Ni, AU]N, and ultra-thin magnetic metal/oxidized barrier is offered. The other part of the article focuses on the optimization and fabrication of CoFeB/MgO/CoFeB p-MTJs, which is thought to have high potential to meet the main demands for non-volatile magnetic random access memory.
基金Supported by the National Natural Science Foundation of China under Grant No 11104091
文摘The doping effects on the frustration and the magnetic properties in hexagonal compounds ot YMn0.9A0.1O3 （A=A1, Fe and Cu） are investigated. Experimental results indicate that both the non-magnetic and magnetic ion dopants lead to the increase of magnetic moments and the decrease of the absolute value of Curie-Weiss temperature （｜θcw｜）- Compared with pure YMnOa, the geometrical frustration of YMn0.9 A0. 1O3 is greatly suppressed and the magnetic coupling in that exhibits dopant-dependent. In addition, for the doped YMno.gAo.103, the antiferromagnetic transition temperature （TN） is also suppressed slightly, which shows an abnormal dilution effect and it may be ascribed to the reduction of frustration due to the chemical substitution.
