地在在磁电机尾巴的血浆表边界层(PSBL ) 的排列水流(FAC ) 分发被从簇 4 点大小分析磁场数据统计上学习。结果证明黄昏方面上的 FAC 分发不在在磁电机尾巴的黎明方面上与那一样。在向地的每个方面和尾巴病房上, FAC 出现是不同的;出...地在在磁电机尾巴的血浆表边界层(PSBL ) 的排列水流(FAC ) 分发被从簇 4 点大小分析磁场数据统计上学习。结果证明黄昏方面上的 FAC 分发不在在磁电机尾巴的黎明方面上与那一样。在向地的每个方面和尾巴病房上, FAC 出现是不同的;出现和在北半球的 FAC 的平均当前的密度与在南部的半球的那些不同。这暗示 FAC 有黄昏黎明方面不对称现象,极性不对称现象并且内部在磁电机尾巴的半球差别。现在的结果在 FAC 机制上为学习给一条好观察证据。展开更多
An experimental muon source(EMuS) will be built at the China Spallation Neutron Source(CSNS). In phase I of CSNS, it has been decided that EMuS will provide a proton beam of 5 kW and 1.6 GeV to generate muon beams. A ...An experimental muon source(EMuS) will be built at the China Spallation Neutron Source(CSNS). In phase I of CSNS, it has been decided that EMuS will provide a proton beam of 5 kW and 1.6 GeV to generate muon beams. A 128-channel muon spin rotation/relaxation/resonance(μSR) spectrometer is proposed as a prototype surface muon spectrometer in a sub-branch of EMuS. The prototype spectrometer includes a detection system, sample environment, and supporting mechanics. The current design has two rings located at the forward and backward directions of the muon spin with 64 detectors per ring. The simulation shows that the highest asymmetry of approximately 0.28 is achieved by utilizing two 10-mm-thick brass degraders. To obtain the optimal asymmetry, the two-ring structure is updated to a four-ring structure with 32 segments in each ring. An asymmetry of 0.42 is obtained through the simulation, which is higher than that of all the current μSR spectrometers in the world.展开更多
The structure and magnetic properties of rare-earth ions Tm^(3+)Kagomé lattice Tm_(3)Sb_(3)Mg_(2)O_(14)are studied by x-ray diffraction,magnetic susceptibility and muon spin relaxation(𝜇SR)experiments.The...The structure and magnetic properties of rare-earth ions Tm^(3+)Kagomé lattice Tm_(3)Sb_(3)Mg_(2)O_(14)are studied by x-ray diffraction,magnetic susceptibility and muon spin relaxation(𝜇SR)experiments.The existence of a small amount of Tm/Mg site-mixing disorder is revealed.DC magnetic susceptibility measurement shows that Tm^(3+)magnetic moments are antiferromagnetically correlated with a negative Curie-Weiss temperature of−26.3 K.Neither long-range magnetic order nor spin-glass transition is observed by DC and AC magnetic susceptibility,and confirmed by μSR experiment down to 0.1 K.However,the emergence of short-range magnetic order is indicated by the zero-field μSR experiments,and the absence of spin dynamics at low temperatures is evidenced by the longitudinal-field μSR technique.Compared with the results of Tm_(3)Sb_(3)Zn_(2)O_(14),another Tm-based Kagomé lattice with much more site-mixing disorder,the gapless spin liquid like behaviors in Tm_(3)Sb_(3)Zn_(2)O_(14)can be induced by disorder effect.Samples with perfect geometrical frustration are in urgent demand to establish whether QSL exists in this kind of materials with rare-earth Kagomé lattice.展开更多
Since Baade's photographic study of M32 in the mid 1940s, it has been accepted as an established fact that M32 is a compact dwarf satellite of M31. The purpose of this paper is to report on the findings of our invest...Since Baade's photographic study of M32 in the mid 1940s, it has been accepted as an established fact that M32 is a compact dwarf satellite of M31. The purpose of this paper is to report on the findings of our investigation into the nature of the existing evidence. We find that the case for M32 being a satellite of M31 rests upon Hubble Space Telescope (HST) based stellar population studies which have resolved red-giant branch (RGB) and red clump stars in M32 as well as other nearby galaxies. Taken in isolation, this recent evidence could be considered to be conclusive in favour of the existing view. However, the conventional scenario does not explain M32's anomalously high central velocity dispersion for a dwarf galaxy (several times that of either NGC 147, NGC 185 or NGC 205) or existing planetary nebula observations (which suggest that M32 is more than twice as distant as M31) and also requires an elaborate physical explanation for M32's inferred compactness. Conversely, we find that the case for M32 being a normal galaxy, of the order of three times as distant as M31, is supported by: (1) a central velocity dispersion typical of intermediate galaxies, (2) the published planetary nebula observations, and (3) known scaling relationships for normal early-type galaxies. However, this novel scenario cannot account for the high apparent luminosities of the RGB stars resolved in the M32 direction by HST observations. We are therefore left with two apparently irreconcilable scenarios, only one of which can be correct, but both of which suffer from potentially fatal evidence to the contrary.This suggests that current understanding of some relevant fields is still very far from adequate.展开更多
We report the synthesis and superconducting properties of a layered cage compound Ba_(3)Rh_(4)Ge_(16).Similar to Ba_(3)Ir_(4)Ge_(16),the compound is composed of 2 D networks of cage units,formed by noncubic Rh-Ge buil...We report the synthesis and superconducting properties of a layered cage compound Ba_(3)Rh_(4)Ge_(16).Similar to Ba_(3)Ir_(4)Ge_(16),the compound is composed of 2 D networks of cage units,formed by noncubic Rh-Ge building blocks,in marked contrast to the reported rattling compounds.The electrical resistivity,magnetization,specific heat capacity,andμSR measurements unveiled moderately coupled s-wave superconductivity with a critical temperature T_(c)=7.0 K,the upper critical field μ_(0)H_(c2)(0)~2.5 T,the electron-phonon coupling strength λ_(e-ph)~0.80,and the Ginzburg-Landau parameterκ~7.89.The mass reduction with the substitution of Ir by Rh is believed to be responsible for the enhancement of T_(c) and coupling between the cage and guest atoms.Our results highlight the importance of atomic weight of framework in cage compounds in controlling the λ_(e-ph) strength and T_(c).展开更多
We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr_(2)GaN.A magnetic phase transition is identified at T≈170 K,whereas no trace of structural transition is observed down to ...We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr_(2)GaN.A magnetic phase transition is identified at T≈170 K,whereas no trace of structural transition is observed down to 6 K.Combining Rietveld refinement with irreducible representations,the spin configuration of Cr ions in Cr_(2)GaN is depicted as an incommensurate sinusoidal modulated structure characterized by a propagating vector k=(0.365,0.365,0).Upon warming up to the paramagnetic state,the magnetic order parameter closely resembles to the temperature dependence of c-axis lattice parameter,suggesting strong magneto-elastic coupling in this compound.Therefore,Cr_(2)Ga N provides a potential platform for exploration of magnetically tuned properties such as magnetoelectric,magnetostrictive and magnetocaloric effects,as well as their applications.展开更多
It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous,asymmetric,weakly magnetized,laser-produced plasma jets can generate strong stochastic magnetic fi...It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous,asymmetric,weakly magnetized,laser-produced plasma jets can generate strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism,provided the magnetic Reynolds number of the plasma is sufficiently large.In this paper,we compare such a plasma with one arising from two pre-magnetized plasma jets whose creation is identical save for the addition of a strong external magnetic field imposed by a pulsed magnetic field generator.We investigate the differences between the two turbulent systems using a Thomson-scattering diagnostic,x-ray selfemission imaging,and proton radiography.The Thomson-scattering spectra and x-ray images suggest that the external magnetic field has a limited effect on the plasma dynamics in the experiment.Although the external magnetic field induces collimation of the flows in the colliding plasma jets and although the initial strengths of the magnetic fields arising from the interaction between the colliding jets are significantly larger as a result of the external field,the energies and morphologies of the stochastic magnetic fields post-amplification are indistinguishable.We conclude that,for turbulent laser-plasmas with supercritical magnetic Reynolds numbers,the dynamo-amplified magnetic fields are determined by the turbulent dynamics rather than the seed fields or modest changes in the initial flow dynamics of the plasma,a finding consistent with theoretical expectations and simulations of turbulent dynamos.展开更多
We systematically investigate the magnetic properties of Cu4-xZnx(OH)6FBr using the neutron diffraction and muon spin rotation and relaxation(μSR) techniques.Neutron-diffraction measurements suggest that the longrang...We systematically investigate the magnetic properties of Cu4-xZnx(OH)6FBr using the neutron diffraction and muon spin rotation and relaxation(μSR) techniques.Neutron-diffraction measurements suggest that the longrange magnetic order and the orthorhombic nuclear structure in the x=0 sample can persist up to x=0.23 and 0.43,respectively.The temperature dependence of the zero-field μSR spectra provides two characteristic temperatures,TA0 and Tλ,which are associated with the initial drop close to zero time and the long-time exponential decay of the muon relaxation,respectively.Comparison between TA0 and TM from previously reported magnetic-susceptibility measurements suggest that the former comes from the short-range interlayer-spin clusters that persist up to x=0.82.On the other hand,the doping level where Tλ becomes zero is about 0.66,which is much higher than threshold of the long-range order,i.e.,~0.4.Our results suggest that the change in the nuclear structure may alter the spin dynamics of the kagome layers and a gapped quantum-spin-liquid state may exist above x=0.66 with the perfect kagome planes.展开更多
Using the Cluster cusp crossings data,dependence of the cusp location at the mid-altitude on the geomagnetic dipole tilt during northward IMF is studied.The results show that the cusp center moves 0.051°Invariant...Using the Cluster cusp crossings data,dependence of the cusp location at the mid-altitude on the geomagnetic dipole tilt during northward IMF is studied.The results show that the cusp center moves 0.051°Invariant Latitude(ILAT)upon the increase of 1°in the dipole tilt angle at the average altitude of 5.8 RE(Earth radius).According to the present results obtained at the altitude of the Cluster orbit and previous results obtained at other altitudes of other satellite orbits,it is found that the higher the altitude in the cusp region is,the bigger the dependence of cusp location on the dipole tilt angle will be.If the altitude increases by 1 RE in the cusp region,the dependence will increase by 0.012°ILAT upon the increase of 1°in the dipole tilt angle.Some possible physical mechanisms are discussed and it shows that the cusp location will be more sensitive to the solar wind dynamic pressure if the altitude is high.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 40674091, 40621003 and 40874084, and the Specialized Research Fund for State Key Laboratories.
文摘地在在磁电机尾巴的血浆表边界层(PSBL ) 的排列水流(FAC ) 分发被从簇 4 点大小分析磁场数据统计上学习。结果证明黄昏方面上的 FAC 分发不在在磁电机尾巴的黎明方面上与那一样。在向地的每个方面和尾巴病房上, FAC 出现是不同的;出现和在北半球的 FAC 的平均当前的密度与在南部的半球的那些不同。这暗示 FAC 有黄昏黎明方面不对称现象,极性不对称现象并且内部在磁电机尾巴的半球差别。现在的结果在 FAC 机制上为学习给一条好观察证据。
基金supported by the National Natural Science Foundation of China(No.11527811)the Key Program of State Key Laboratory of Particle Detection and ElectronicsA part of the work performed in the UKRI ISIS Detector Group was sponsored by the China Scholarship Council
文摘An experimental muon source(EMuS) will be built at the China Spallation Neutron Source(CSNS). In phase I of CSNS, it has been decided that EMuS will provide a proton beam of 5 kW and 1.6 GeV to generate muon beams. A 128-channel muon spin rotation/relaxation/resonance(μSR) spectrometer is proposed as a prototype surface muon spectrometer in a sub-branch of EMuS. The prototype spectrometer includes a detection system, sample environment, and supporting mechanics. The current design has two rings located at the forward and backward directions of the muon spin with 64 detectors per ring. The simulation shows that the highest asymmetry of approximately 0.28 is achieved by utilizing two 10-mm-thick brass degraders. To obtain the optimal asymmetry, the two-ring structure is updated to a four-ring structure with 32 segments in each ring. An asymmetry of 0.42 is obtained through the simulation, which is higher than that of all the current μSR spectrometers in the world.
基金the ISIS cryogenics Group for their valuable help during the μSR experiments (10.5286/ISIS.E.RB1820271)supported by the National Natural Science Foundation of China (Grant Nos.12034004 and 12174065)the Shanghai Municipal Science and Technology (Major Project Grant Nos.2019SHZDZX01 and 20ZR1405300)
文摘The structure and magnetic properties of rare-earth ions Tm^(3+)Kagomé lattice Tm_(3)Sb_(3)Mg_(2)O_(14)are studied by x-ray diffraction,magnetic susceptibility and muon spin relaxation(𝜇SR)experiments.The existence of a small amount of Tm/Mg site-mixing disorder is revealed.DC magnetic susceptibility measurement shows that Tm^(3+)magnetic moments are antiferromagnetically correlated with a negative Curie-Weiss temperature of−26.3 K.Neither long-range magnetic order nor spin-glass transition is observed by DC and AC magnetic susceptibility,and confirmed by μSR experiment down to 0.1 K.However,the emergence of short-range magnetic order is indicated by the zero-field μSR experiments,and the absence of spin dynamics at low temperatures is evidenced by the longitudinal-field μSR technique.Compared with the results of Tm_(3)Sb_(3)Zn_(2)O_(14),another Tm-based Kagomé lattice with much more site-mixing disorder,the gapless spin liquid like behaviors in Tm_(3)Sb_(3)Zn_(2)O_(14)can be induced by disorder effect.Samples with perfect geometrical frustration are in urgent demand to establish whether QSL exists in this kind of materials with rare-earth Kagomé lattice.
文摘Since Baade's photographic study of M32 in the mid 1940s, it has been accepted as an established fact that M32 is a compact dwarf satellite of M31. The purpose of this paper is to report on the findings of our investigation into the nature of the existing evidence. We find that the case for M32 being a satellite of M31 rests upon Hubble Space Telescope (HST) based stellar population studies which have resolved red-giant branch (RGB) and red clump stars in M32 as well as other nearby galaxies. Taken in isolation, this recent evidence could be considered to be conclusive in favour of the existing view. However, the conventional scenario does not explain M32's anomalously high central velocity dispersion for a dwarf galaxy (several times that of either NGC 147, NGC 185 or NGC 205) or existing planetary nebula observations (which suggest that M32 is more than twice as distant as M31) and also requires an elaborate physical explanation for M32's inferred compactness. Conversely, we find that the case for M32 being a normal galaxy, of the order of three times as distant as M31, is supported by: (1) a central velocity dispersion typical of intermediate galaxies, (2) the published planetary nebula observations, and (3) known scaling relationships for normal early-type galaxies. However, this novel scenario cannot account for the high apparent luminosities of the RGB stars resolved in the M32 direction by HST observations. We are therefore left with two apparently irreconcilable scenarios, only one of which can be correct, but both of which suffer from potentially fatal evidence to the contrary.This suggests that current understanding of some relevant fields is still very far from adequate.
基金Supported the National Key R&D Program of China(Grant No.2018YFA0704300)the National Natural Science Foundation of China(Grant Nos.U1932217,11974246,and 12004252)+5 种基金the Natural Science Foundation of Shanghai(Grant No.19ZR1477300)the Science and Technology Commission of Shanghai Municipality(Grant No.19JC1413900)the Analytical Instrumentation Center,SPST,Shanghai Tech University(Grant No.SPST-AIC10112914)the SERB,India for Core Research grant supportUK-India Newton Funding for funding supportthe Royal Society of London for Newton Advanced Fellowship funding and International Exchange funding between UK and JapanISIS Facility for beam time(Grant No.RB1968041)。
文摘We report the synthesis and superconducting properties of a layered cage compound Ba_(3)Rh_(4)Ge_(16).Similar to Ba_(3)Ir_(4)Ge_(16),the compound is composed of 2 D networks of cage units,formed by noncubic Rh-Ge building blocks,in marked contrast to the reported rattling compounds.The electrical resistivity,magnetization,specific heat capacity,andμSR measurements unveiled moderately coupled s-wave superconductivity with a critical temperature T_(c)=7.0 K,the upper critical field μ_(0)H_(c2)(0)~2.5 T,the electron-phonon coupling strength λ_(e-ph)~0.80,and the Ginzburg-Landau parameterκ~7.89.The mass reduction with the substitution of Ir by Rh is believed to be responsible for the enhancement of T_(c) and coupling between the cage and guest atoms.Our results highlight the importance of atomic weight of framework in cage compounds in controlling the λ_(e-ph) strength and T_(c).
基金supported by the National Natural Science Foundation of China(Grant Nos.11822411,12061130200,11961160699,11974392,and 52101236)the National Key Research and Development Program of China(Grant Nos.2018YFA0704200,2017YFA0303100,and 2020YFA0406003)+4 种基金the Strategic Priority Research Program(B)of the CAS(GrantNo.XDB25000000)K.C.Wong Education Foundation(Grant No.GJTD-2020-01)the Youth Innovation Promotion Association of the CAS(Grant No.Y202001)Beijing Natural Science Foundation(Grant No.JQ19002)the Newton Advanced Fellowship funding from the Royal Society of UK(Grant No.NAFR1201248)。
文摘We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr_(2)GaN.A magnetic phase transition is identified at T≈170 K,whereas no trace of structural transition is observed down to 6 K.Combining Rietveld refinement with irreducible representations,the spin configuration of Cr ions in Cr_(2)GaN is depicted as an incommensurate sinusoidal modulated structure characterized by a propagating vector k=(0.365,0.365,0).Upon warming up to the paramagnetic state,the magnetic order parameter closely resembles to the temperature dependence of c-axis lattice parameter,suggesting strong magneto-elastic coupling in this compound.Therefore,Cr_(2)Ga N provides a potential platform for exploration of magnetically tuned properties such as magnetoelectric,magnetostrictive and magnetocaloric effects,as well as their applications.
基金the European Research Council(ERC)under the European Community’s Seventh Framework Programme(Grant No.FP7/2007-2013,ERC Grant Agreement Nos.256973 and 247039)the National Nuclear Security Administration(NNSA)of the U.S.Department of Energy(DOE)under Contract No.B591485+12 种基金Lawrence Livermore National Laboratory(LLNL),Field Work Proposal No.57789Argonne National Laboratory,Subcontract Nos.536203 and 630138Los Alamos National Laboratory,Subcontract No.B632670LLNL,Grant Nos.DE-NA0002724,DE-NA0003605,and DE-NA0003934the Flash Center for Computational Science,Grant No.DE-NA0003868the Massachusetts Institute of Technology,and Cooperative Agreement No.DE-NA0003856the Laboratory for Laser Energetics at the University of Rochester.the U.S.DOE Office of Science Fusion Energy Sciences(Grant No.DE-SC0016566)the National Science Foundation(Grant Nos.PHY-1619573,PHY-2033925,and PHY-2045718)the National Research Foundation of Korea(Grant Nos.2016R1A5A1013277 and 2020R1A2C2102800)Support from AWE plc.,the Engineering and Physical Sciences Research Council(Grant Nos.EP/M022331/1,EP/N014472/1,and EP/R034737/1)the U.K.Science and Technology Facilities Council is also acknowledged.General Atomics for target manufacturing and R&D support,which was funded by the NNSA in support of the National Laser Users’Facility program(Subcontract Nos.89233118CNA000010 and 89233119CNA000063).
文摘It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous,asymmetric,weakly magnetized,laser-produced plasma jets can generate strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism,provided the magnetic Reynolds number of the plasma is sufficiently large.In this paper,we compare such a plasma with one arising from two pre-magnetized plasma jets whose creation is identical save for the addition of a strong external magnetic field imposed by a pulsed magnetic field generator.We investigate the differences between the two turbulent systems using a Thomson-scattering diagnostic,x-ray selfemission imaging,and proton radiography.The Thomson-scattering spectra and x-ray images suggest that the external magnetic field has a limited effect on the plasma dynamics in the experiment.Although the external magnetic field induces collimation of the flows in the colliding plasma jets and although the initial strengths of the magnetic fields arising from the interaction between the colliding jets are significantly larger as a result of the external field,the energies and morphologies of the stochastic magnetic fields post-amplification are indistinguishable.We conclude that,for turbulent laser-plasmas with supercritical magnetic Reynolds numbers,the dynamo-amplified magnetic fields are determined by the turbulent dynamics rather than the seed fields or modest changes in the initial flow dynamics of the plasma,a finding consistent with theoretical expectations and simulations of turbulent dynamos.
基金Supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0302900,2016YFA0300500,2018YFA0704200,2017YFA0303100,and 2016YFA0300600)the National Natural Science Foundation of China(Grant Nos.11874401,11674406,11674372,11961160699,11774399,12061130200,11974392,and 11822411)+4 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDB25000000,XDB07020000,XDB33000000,and XDB28000000)the Beijing Natural Science Foundation(Grant Nos.Z180008 and JQ19002)Guangdong Introducing Innovative and Entrepreneurial Teams(Grant No.2017ZT07C062)the Youth Innovation Promotion Association of CAS(Grant No.2016004)the Royal Society-Newton Advanced Fellowship(Grant No.NAF∖R1∖201248).
文摘We systematically investigate the magnetic properties of Cu4-xZnx(OH)6FBr using the neutron diffraction and muon spin rotation and relaxation(μSR) techniques.Neutron-diffraction measurements suggest that the longrange magnetic order and the orthorhombic nuclear structure in the x=0 sample can persist up to x=0.23 and 0.43,respectively.The temperature dependence of the zero-field μSR spectra provides two characteristic temperatures,TA0 and Tλ,which are associated with the initial drop close to zero time and the long-time exponential decay of the muon relaxation,respectively.Comparison between TA0 and TM from previously reported magnetic-susceptibility measurements suggest that the former comes from the short-range interlayer-spin clusters that persist up to x=0.82.On the other hand,the doping level where Tλ becomes zero is about 0.66,which is much higher than threshold of the long-range order,i.e.,~0.4.Our results suggest that the change in the nuclear structure may alter the spin dynamics of the kagome layers and a gapped quantum-spin-liquid state may exist above x=0.66 with the perfect kagome planes.
基金supported by the National Natural Science Foundation of China(41004076,41274146 and 41074114)the Specialized Research Fund for State Key Laboratories
文摘Using the Cluster cusp crossings data,dependence of the cusp location at the mid-altitude on the geomagnetic dipole tilt during northward IMF is studied.The results show that the cusp center moves 0.051°Invariant Latitude(ILAT)upon the increase of 1°in the dipole tilt angle at the average altitude of 5.8 RE(Earth radius).According to the present results obtained at the altitude of the Cluster orbit and previous results obtained at other altitudes of other satellite orbits,it is found that the higher the altitude in the cusp region is,the bigger the dependence of cusp location on the dipole tilt angle will be.If the altitude increases by 1 RE in the cusp region,the dependence will increase by 0.012°ILAT upon the increase of 1°in the dipole tilt angle.Some possible physical mechanisms are discussed and it shows that the cusp location will be more sensitive to the solar wind dynamic pressure if the altitude is high.