In this work we report that after single-walled carbon nanotubes(SWNTs) are sheared with a pair of titanium scissors,the magnetization becomes larger than that of the corresponding pristine ones. The magnetization inc...In this work we report that after single-walled carbon nanotubes(SWNTs) are sheared with a pair of titanium scissors,the magnetization becomes larger than that of the corresponding pristine ones. The magnetization increases proportionally with the number of SWNTs with sheared ends, suggesting that there exist magnetic moments at the sheared ends of SWNTs.By using the coefficient of this linear relation, the average magnetic moment is estimated to be 41.5 ± 9.8 μB(Bohr magneton) per carbon atom in the edge state at temperature of 300.0 K, suggesting that ultrahigh magnetic fields can be produced. The dangling sigma and pi bonds of the carbon atoms at sheared ends play important roles in determining the unexpectedly high magnetic moments, which may have great potential applications.展开更多
The attractions of cantilevers made of multiwalled carbon nanotubes（MWNTs） and secured on one end are studied in the non-uniform magnetic field of a permanent magnet. Under an optical microscope, the positions and t...The attractions of cantilevers made of multiwalled carbon nanotubes（MWNTs） and secured on one end are studied in the non-uniform magnetic field of a permanent magnet. Under an optical microscope, the positions and the corresponding deflections of the original cantilevers（with iron catalytic nanoparticles at the free end） and corresponding cut-off cantilevers（the free ends consisting of open ends of MWNTs） are studied. Both kinds of CNT cantilevers are found to be attracted by the magnet, and the point of application of force is proven to be at the tip of the cantilever. By measuring and comparing deflections between these two kinds of cantilevers, the magnetic moment at the open ends of the CNTs can be quantified.Due to the unexpectedly high value of the magnetic moment at the open ends of carbon nanotubes, it is called giant magnetic moment, and its possible mechanisms are proposed and discussed.展开更多
A method based on the measurement of Fe average atomic magnetic moment to identify the structural transition caused by the increase of Ga content in quenched Fe1-xGax alloys （0.15 ≤ x ≤0.30） is proposed. The quenc...A method based on the measurement of Fe average atomic magnetic moment to identify the structural transition caused by the increase of Ga content in quenched Fe1-xGax alloys （0.15 ≤ x ≤0.30） is proposed. The quenched Fe1-xGax alloys show a change of the Fe average atomic magnetic moment from 2.25μB to 1.78μB and then to 1.58μB, which corresponds to the structural transition from A2 to D03 and then to B2. The relationship between the structure and the magnetostriction is clarified, and the maximum magnetostriction appears in the A2 phase. The variation tendency of the magnetostriction is well characterized, which also reflects the structural transition.展开更多
Spin-valley polarization and bandgap regulation are critical in the developing of quantum devices.Here,by employing the density functional theory,we investigate the effects of stacking form,thickness and magnetic mome...Spin-valley polarization and bandgap regulation are critical in the developing of quantum devices.Here,by employing the density functional theory,we investigate the effects of stacking form,thickness and magnetic moment in the electronic structures of WSe_(2)–MoS_(2)heterostructures.Calculations show that spin-valley polarization maintains in all situations.Increasing thickness of 2H-MoS_(2)not only tunes the bandgap but also changes the degeneracy of the conduction band minimums(CBM)at K/K_(1) points.Gradual increase of micro magnetic moment tunes the bandgap and raises the valence band maximums(VBM)atΓpoint.In addition,the regulation of band gap by the thickness of 2H-MoS_(2)and introduced magnetic moment depends on the stacking type.Results suggest that WSe_(2)–MoS_(2)heterostructure supports an ideal platform for valleytronics applications.Our methods also give new ways of optical absorption regulation in spin-valley devices.展开更多
In order to understand the Kondo effect observed in molecular systems, first-principles calculations have been widely used to predict the ground state properties of molecules on metal substrates. In this work, the int...In order to understand the Kondo effect observed in molecular systems, first-principles calculations have been widely used to predict the ground state properties of molecules on metal substrates. In this work, the interaction and the local magnetic moments of magnetic molecules （3d-metal phthalocyanine and tetraphenylporphyrin molecules） on noble metal surfaces are investigated based on the density functional theory. The calculation results show that the dz2 orbital of the transition metal atom of the molecule plays a dominant role in the molecule-surface interaction and the adsorption energy exhibits a simple declining trend as the adsorption distance increases. In addition, the Au（111） surface generally has a weak interaction with the adsorbed molecule compared with the Cu（ll 1） surface and thus serves as a better candidate substrate for studying the Kondo effect. The relation between the local magnetic moment and the Coulomb interaction U is examined by carrying out the GGA＋U calculation according to Dudarev＇s scheme. We find that the Coulomb interaction is essential for estimating the local magnetic moment in molecule-surface systems, and we suggest that the reference values of parameter U are 2 eV for Fe and 2-3 eV for Co.展开更多
In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic pro...In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment mr of 1.1 kg dummy copper test mass, and the measurement result is(6.45 ± 0.04(stat) ± 0.07(syst)) × 10^(-8)A · m^(2). The measurement precision of the mr is about 0.9 n A · m^(2), well below the present measurement requirement of Tian Qin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.展开更多
Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. Th...Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μ_(v) = 2.1 × 10^(-11)μ_(B).However, tritium backgrounds or solar axion interaction in this energy window are equally plausible causes.Upcoming multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton·year exposure of liquid scintillator to solar neutrinos, a sensitivity of μ_(v) < 10^(-11)μ_(B) can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present.展开更多
Several rocksalt Sr4X3N （X = O, S, Se, and Te） are predicted to be potential half-metallic ferromagnets free of transition-metal and rare-earth elements by performing the first-principles calculations. Then their ma...Several rocksalt Sr4X3N （X = O, S, Se, and Te） are predicted to be potential half-metallic ferromagnets free of transition-metal and rare-earth elements by performing the first-principles calculations. Then their magnetic properties, such as the half metallicity and the crystal-cell magnetic moments are investigated. The Sr4X3N possibly have higher Curie temperatures and have more stable half metallicity than the Sr4X3C. Their crystal-cell magnetic moments are all 1.00 μB. The crystal-cell magnetic moments and the half metallicity arise mainly from the N ions. The main mechanism is the strong covalent interaction leading to the sp2 hybridized orbitals in the Sr4X3N. Then two Sr-5s and three N-2p electrons enter into three sp2 hybridized orbitals. Among these five electrons, four electrons are paired and one is unpaired, so there are three spin-up electrons and two spin-down electrons in these sp2 hybridized orbitals.展开更多
The 2×2× 1 rocksalt C-doped MgS supercells are optimized and their magnetic and electric properties, including the half-metallicity, the conductivity and the supercell magnetic moments, are calculated or ana...The 2×2× 1 rocksalt C-doped MgS supercells are optimized and their magnetic and electric properties, including the half-metallicity, the conductivity and the supercell magnetic moments, are calculated or analysed by the first- principles researches based on the density functional theory. Results show that the concentration of C-dopants may cause important influence on the magnetic and the electric properties of rocksalt MgS. C dopants are inclined to have a scattering distribution. MGC0.0625S0.9375^, aMgC0.1250S0.8750 and MgC0.1875S0.8125 have evident half-metallicity. They have wide spin energy gaps, thus high Curie temperature possibly. Their supercell magnetic moments are near to integral numbers 2.0, 4.0 and 6.0μB. The main reason for spin polarization and half-metallicity of C-doped MgS is that there are sp hybridized orbitals in ligand compound ML6 caused by covalent interaction between C-ions and Mg-ions.展开更多
A dip of the transverse component of the magnetic moment as a function of resonance frequency-detuning will emerge when the intensity of oscillating magnetic field exceeds a specific value, which is demonstrated theor...A dip of the transverse component of the magnetic moment as a function of resonance frequency-detuning will emerge when the intensity of oscillating magnetic field exceeds a specific value, which is demonstrated theoretically and experimentally. The linewidth of magnetic-resonance signal can be much smaller than when the Mx–MR magnetometer operates on condition that the intensity of oscillating magnetic field is smaller than this specific value, and the Mx–MR magnetometer can possess a much higher signal-to-noise ratio. The experimental result shows that the sensitivity of Mx–MR magnetometer can be improved by an order of magnitude under this condition.展开更多
By employing the spin resolved density functional theory, half-metallic character is investigated in Cs2NpBr6 having a K2PtCl6-type structure. The results precisely predict the half-metallic behavior of Cs2NpBr6. In s...By employing the spin resolved density functional theory, half-metallic character is investigated in Cs2NpBr6 having a K2PtCl6-type structure. The results precisely predict the half-metallic behavior of Cs2NpBr6. In spin-down state it presents an indirect band gap, while in spin-up channel it turns metallic. The structure optimization confirms the half-metallic nature in ferromagnetic configuration. The calculated magnetic moment is 3 μB toward which the main contributor is the Np atom.Furthermore, all the computed results are compared with the available experimental and theoretical values. According to the present analysis, we recommend Cs2NpBr6 for spintronic applications.展开更多
The electronic structures and magnetic properties of SmCo7-xMx （M=Ti, Si, Zr, Hf, Cu, B, Ag, Ga, Mn） compounds are investigated by using a spin-polarized MS-Xα method. The results show that the long-range ferromagn...The electronic structures and magnetic properties of SmCo7-xMx （M=Ti, Si, Zr, Hf, Cu, B, Ag, Ga, Mn） compounds are investigated by using a spin-polarized MS-Xα method. The results show that the long-range ferromagnetic order is determined by a stronger 3d-5d interaction, rather than the traditional RKKY interaction, and the effects of doping element M on 3d-5d coupling are negligible in Sm-Co-based compounds. The nonmagnetic dopant Si atoms have a larger effect on the moments of 2e site although they preferably occupy the Co 3g sites, which results in the stronger uniaxial anisotropy of this compound. Analysis of the formation energies indicates that 5d-element doped compounds are more stable than other dopants, and furthermore, they have a higher Curie temperature above room temperature, which will be in favor of their potential application as high-temperature permanent magnets.展开更多
The structural stability and magnetic properties of the icosahedral Ni13, Ni13^＋1 and Ni13^-1 clusters have been obtained by utilizing all-electron density functional theory with the generalized gradient approximatio...The structural stability and magnetic properties of the icosahedral Ni13, Ni13^＋1 and Ni13^-1 clusters have been obtained by utilizing all-electron density functional theory with the generalized gradient approximations for the exchange-correlation energy. The calculated results show that the ground states of neutral and charged clusters all favour a D3d structure, a distorted icosahedron, due to the Jahn-Teller effect. The radial distortions caused by doping one electron and by doping one hole are opposite to each other. Doping one electron will result in a 1/2 decrease and doping one hole will result in a 1/2 increase of the total spin. Both increasing interatomic spacing and decreasing coordination will lead to an enhancement of the spin magnetic moments for Nil3 clusters.展开更多
Electronic and magnetic structures of zinc blende ZnO doped with V impurities are studied by first-principles calculations based on the Korringa-Kohn-Rostoker （KKR） method combined with the coherent potential approx...Electronic and magnetic structures of zinc blende ZnO doped with V impurities are studied by first-principles calculations based on the Korringa-Kohn-Rostoker （KKR） method combined with the coherent potential approximation （CPA）. Calculations for the substitution of O by N or P are performed and the magnetic moment is found to be sensitive to the N or P content. Furthermore, the system exhibits a half-metallic band structure accompanied by the broadening of vanadium bands. The mechanism responsible for ferromagnetism is also discussed and the stability of the ferromagnetic state compared with that of the paramagnetic state is systematically investigated by calculating the total energy difference between them by using supercell method.展开更多
Based on ab initio total energy calculations, the structural, electronic, mechanic, and magnetic properties of PdHx are investigated. It is found that bulk modulus of PdHx is larger than the metM Pd with the hydrogen ...Based on ab initio total energy calculations, the structural, electronic, mechanic, and magnetic properties of PdHx are investigated. It is found that bulk modulus of PdHx is larger than the metM Pd with the hydrogen storage except Pd4H2. The calculated results for the magnetic moments show that the hydrogen addition weakens the magnetic properties of the PdHx systems. A strong magneto-volume effect is found in PdHx structures as well as Pd. The transition from paramagnetism to ferromagnetism is discussed. The corresponding densities of states for both structures are also shown to understand the magnetic behaviour.展开更多
Self-consistent ab initio calculations, based on the density functional theory （DFT） and using the full potential linear augmented plane wave （FLAPW） method, are performed to investigate both electronic and magnet...Self-consistent ab initio calculations, based on the density functional theory （DFT） and using the full potential linear augmented plane wave （FLAPW） method, are performed to investigate both electronic and magnetic properties of the MnS layers. Polarized spin and spin-orbit coupling are included in the calculations within the framework of the antiferromagnetic state between two adjacent Mn layers. Magnetic moments considered to lie along axes are computed. Obtained data from ab initio calculations are used as input data for the high temperature series expansion （HTSE） calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the spin-4.39 nearest-neighbour Heisenberg model on centred face cubic （FCC） and lattices is thoroughly analysed by a power series coherent anomaly method （CAM）. The exchange interactions between the magnetic atoms, the N@el temperature, and the critical exponent associated with the magnetic susceptibility are obtained for the MnS layer.展开更多
s The geometrical structures of Cd0.75TM0.25Se （TM = Ti, V, Cr and Mn） are optimized, and then their electric and magnetic properties are investigated by performing first-principles calculations within the generaliz...s The geometrical structures of Cd0.75TM0.25Se （TM = Ti, V, Cr and Mn） are optimized, and then their electric and magnetic properties are investigated by performing first-principles calculations within the generalized gradient approximation for the exchange-correlation function based on density functional theory. Cd0.75TM0.25Se （TM =Ti and V） are found to have high spin-polarization near 100% at the Fermi level. Cd0.75TM0.25Se （TM = Cr and Mn） are half-metallic ferromagnets whose spin-polarization at the Fermi level is absolutely ＋100%. The supercell magnetic moments of Cd0.75Cr0.25Se and Cdo.75Mno.25Se are 4.00 and 5.00 μB, which arise mainly from Cr-ions and Mnions, respectively. The half-metallicity of Cdo.75Cro.25Se is more stable than that of Cd0.75Mn0.25Se. The electronic structures of Cr-ions and Mn-ions are Cr eg2↑t22g↑ and Mn e2 3 ↑t23g↑, respectively.展开更多
The stable geometries,electronic structures,and magnetic behaviors of the ScLin(n=2-13)clusters are investigated by using particle swarm optimization(PSO)and density functional theory(DFT).The results show that these ...The stable geometries,electronic structures,and magnetic behaviors of the ScLin(n=2-13)clusters are investigated by using particle swarm optimization(PSO)and density functional theory(DFT).The results show that these clusters have three-dimensional(3D)structures except ScLi2,and ScLi12,and ScLi13 that possess the cage-like structures.In analyses of the average binding energy,second-order difference of energy,and fragmentation energy,ScLi12 cluster is identified as magnetic superatom.The magnetic moment for each of these clusters owns an oscillating curve of different cluster sizes,and their magnetic moments are further investigated using molecular orbitals and jellium model.Of ScLin(n=2-13)clusters,ScLi12 has the largest spin magnetic moment(3µB),and molecular orbitals of ScLi12 can be described as 1S^21P^61D^5αD^2β.Additionally,Mulliken population and AdNDP bonding analysis are discussed and the results reveal that the Sc atom and Lin atoms make equal contribution to the total magnetic moment,and atomic charges transfer between Sc atoms and Li atoms.展开更多
Electron magnetic circular dichroism opens a new door to explore magnetic properties by transmitted electrons in the transmission electron microscope. However, obtaining quantitative magnetic parameters, such as spin ...Electron magnetic circular dichroism opens a new door to explore magnetic properties by transmitted electrons in the transmission electron microscope. However, obtaining quantitative magnetic parameters, such as spin and orbital magnetic moment with element-specificity, goes a long way along with the development and improvement of this technique both in theoretical and experimental aspects. In this review, we will give a detailed description of the quantitative electron magnetic circular dichroism（EMCD） technique to measure magnetic parameters with spin-specificity, element-specificity,site-specificity, and orbital-spin-specificity. The discussion completely contains the procedures from raw experimental data acquisition to final magnetic parameters, together with the related custom code we have developed.展开更多
Using the first-principles calculations, we study the structural, electronic, and magnetic properties of vanadium adsorbed MoSe_2 monolayer, and the magnetic couplings between the V adatoms at different adsorption con...Using the first-principles calculations, we study the structural, electronic, and magnetic properties of vanadium adsorbed MoSe_2 monolayer, and the magnetic couplings between the V adatoms at different adsorption concentrations. The calculations show that the V atom is chemically adsorbed on the MoSe_2 monolayer and prefers the location on the top of an Mo atom surrounded by three nearest-neighbor Se atoms. The interatomic electron transfer from the V to the nearestneighbor Se results in the polarized covalent bond with weak covalency, associated with the hybridizations of V with Se and Mo. The V adatom induces local impurity states in the middle of the band gap of pristine MoSe_2, and the peak of density of states right below the Fermi energy is associated with the V- dz^2 orbital. A single V adatom induces a magnetic moment of 5 μBthat mainly distributes on the V-3d and Mo-4d orbitals. The V adatom is in high-spin state, and its local magnetic moment is associated with the mid-gap impurity states that are mainly from the V-3d orbitals. In addition,the crystal field squashes a part of the V-4s electrons into the V-3d orbitals, which enhances the local magnetic moment.The magnetic ground states at different adsorption concentrations are calculated by generalized gradient approximations（GGA） and GGA＋U with enhanced electron localization. In addition, the exchange integrals between the nearest-neighbor V adatoms at different adsorption concentrations are calculated by fitting the first-principle total energies of ferromagnetic（FM） and antiferromagnetic（AFM） states to the Heisenberg model. The calculations with GGA show that there is a transition from ferromagnetic to antiferromagnetic ground state with increasing the distance between the V adatoms. We propose an exchange mechanism based on the on-site exchange on Mo and the hybridization between Mo and V, to explain the strong ferromagnetic coupling at a short distance between the V adatoms. However, the ferromagnetic exchange mechanism is sensitive to both the increased inter-adatom distance at low concentration and the enhanced electron localization by GGA＋U, which leads to antiferromagnetic ground state, where the antiferromagnetic superexchange is dominant.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0208403 and 2016YFA0200403)the National Natural Science Foundation of China(Grant Nos.51472057,11874129,91323304,and 11674387)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA09040101)the Baotou Rare Earth Research and Development Centre,Chinese Academy of Sciences(Grant No.GZR 2018001)
文摘In this work we report that after single-walled carbon nanotubes(SWNTs) are sheared with a pair of titanium scissors,the magnetization becomes larger than that of the corresponding pristine ones. The magnetization increases proportionally with the number of SWNTs with sheared ends, suggesting that there exist magnetic moments at the sheared ends of SWNTs.By using the coefficient of this linear relation, the average magnetic moment is estimated to be 41.5 ± 9.8 μB(Bohr magneton) per carbon atom in the edge state at temperature of 300.0 K, suggesting that ultrahigh magnetic fields can be produced. The dangling sigma and pi bonds of the carbon atoms at sheared ends play important roles in determining the unexpectedly high magnetic moments, which may have great potential applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10774032 and 51472057)the Instrument Developing Project of the Chinese Academy of Sciences(Grant No.Y2010031)
文摘The attractions of cantilevers made of multiwalled carbon nanotubes（MWNTs） and secured on one end are studied in the non-uniform magnetic field of a permanent magnet. Under an optical microscope, the positions and the corresponding deflections of the original cantilevers（with iron catalytic nanoparticles at the free end） and corresponding cut-off cantilevers（the free ends consisting of open ends of MWNTs） are studied. Both kinds of CNT cantilevers are found to be attracted by the magnet, and the point of application of force is proven to be at the tip of the cantilever. By measuring and comparing deflections between these two kinds of cantilevers, the magnetic moment at the open ends of the CNTs can be quantified.Due to the unexpectedly high value of the magnetic moment at the open ends of carbon nanotubes, it is called giant magnetic moment, and its possible mechanisms are proposed and discussed.
基金Project supported by the National Science Fund for Distinguished Young Scholars of China (Grant No.50925101)the Innovation Foundation of Beihang University for Ph.D.Graduates,China
文摘A method based on the measurement of Fe average atomic magnetic moment to identify the structural transition caused by the increase of Ga content in quenched Fe1-xGax alloys （0.15 ≤ x ≤0.30） is proposed. The quenched Fe1-xGax alloys show a change of the Fe average atomic magnetic moment from 2.25μB to 1.78μB and then to 1.58μB, which corresponds to the structural transition from A2 to D03 and then to B2. The relationship between the structure and the magnetostriction is clarified, and the maximum magnetostriction appears in the A2 phase. The variation tendency of the magnetostriction is well characterized, which also reflects the structural transition.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61975224 and 12104004)the University Synergy Innovation Program of Anhui Province(Grant No.GXXT-2020-050)+2 种基金the Fund of Anhui Provincial Natural Science Foundation(Grant No.2008085MF206)New magnetoelectric materials and devices,the Recruitment Program for Leading Talent Team of Anhui Province 2020,State Key Laboratory of Luminescence and Applications(Grant No.SKLA-2021-03)the Open Fund of Infrared and Low-Temperature Plasma Key Laboratory of Anhui Province(Grant No.IRKL2022KF03)。
文摘Spin-valley polarization and bandgap regulation are critical in the developing of quantum devices.Here,by employing the density functional theory,we investigate the effects of stacking form,thickness and magnetic moment in the electronic structures of WSe_(2)–MoS_(2)heterostructures.Calculations show that spin-valley polarization maintains in all situations.Increasing thickness of 2H-MoS_(2)not only tunes the bandgap but also changes the degeneracy of the conduction band minimums(CBM)at K/K_(1) points.Gradual increase of micro magnetic moment tunes the bandgap and raises the valence band maximums(VBM)atΓpoint.In addition,the regulation of band gap by the thickness of 2H-MoS_(2)and introduced magnetic moment depends on the stacking type.Results suggest that WSe_(2)–MoS_(2)heterostructure supports an ideal platform for valleytronics applications.Our methods also give new ways of optical absorption regulation in spin-valley devices.
基金supported by the National Natural Science Foundation of China (Grant No. 51210003)the National Basic Research Program of China (Grant Nos. 2011CB921702 and 2011CB808401)
文摘In order to understand the Kondo effect observed in molecular systems, first-principles calculations have been widely used to predict the ground state properties of molecules on metal substrates. In this work, the interaction and the local magnetic moments of magnetic molecules （3d-metal phthalocyanine and tetraphenylporphyrin molecules） on noble metal surfaces are investigated based on the density functional theory. The calculation results show that the dz2 orbital of the transition metal atom of the molecule plays a dominant role in the molecule-surface interaction and the adsorption energy exhibits a simple declining trend as the adsorption distance increases. In addition, the Au（111） surface generally has a weak interaction with the adsorbed molecule compared with the Cu（ll 1） surface and thus serves as a better candidate substrate for studying the Kondo effect. The relation between the local magnetic moment and the Coulomb interaction U is examined by carrying out the GGA＋U calculation according to Dudarev＇s scheme. We find that the Coulomb interaction is essential for estimating the local magnetic moment in molecule-surface systems, and we suggest that the reference values of parameter U are 2 eV for Fe and 2-3 eV for Co.
基金supported by the National Key R&D Program of China (Grant No. 2020YFC2200500)the National Natural Science Foundation of China (Grant Nos. 12075325, 12005308, and 11605065)。
文摘In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment mr of 1.1 kg dummy copper test mass, and the measurement result is(6.45 ± 0.04(stat) ± 0.07(syst)) × 10^(-8)A · m^(2). The measurement precision of the mr is about 0.9 n A · m^(2), well below the present measurement requirement of Tian Qin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA10010800)the Double First Class Start-up Fund (WF220442603) provided by Shanghai Jiao Tong Universitysupport from the CAS Center for Excellence in Particle Physics (CCEPP)。
文摘Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μ_(v) = 2.1 × 10^(-11)μ_(B).However, tritium backgrounds or solar axion interaction in this energy window are equally plausible causes.Upcoming multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton·year exposure of liquid scintillator to solar neutrinos, a sensitivity of μ_(v) < 10^(-11)μ_(B) can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present.
基金Project supported by Chongqing Natural Science Foundation,China (Grant Nos.CSCT2010BB4405 and CSTC2008BB4083)the Doctoral Foundation of Chongqing University of Posts and Telecommunications,China(Grant No.A2008-63)
文摘Several rocksalt Sr4X3N （X = O, S, Se, and Te） are predicted to be potential half-metallic ferromagnets free of transition-metal and rare-earth elements by performing the first-principles calculations. Then their magnetic properties, such as the half metallicity and the crystal-cell magnetic moments are investigated. The Sr4X3N possibly have higher Curie temperatures and have more stable half metallicity than the Sr4X3C. Their crystal-cell magnetic moments are all 1.00 μB. The crystal-cell magnetic moments and the half metallicity arise mainly from the N ions. The main mechanism is the strong covalent interaction leading to the sp2 hybridized orbitals in the Sr4X3N. Then two Sr-5s and three N-2p electrons enter into three sp2 hybridized orbitals. Among these five electrons, four electrons are paired and one is unpaired, so there are three spin-up electrons and two spin-down electrons in these sp2 hybridized orbitals.
基金Project supported by the Chongqing Natural Science Foundation,China(Grant Nos.CSTC2007BB4391,CSTC2007BB2448 and CSTC2008BB4083)the Chongqing Science and Technology Foundation,China(Grant Nos.KJ060515 and KJ080518)the Doctoral Foundation of Chongqing University of Posts and Telecommunications(Grant No.A2008-63)
文摘The 2×2× 1 rocksalt C-doped MgS supercells are optimized and their magnetic and electric properties, including the half-metallicity, the conductivity and the supercell magnetic moments, are calculated or analysed by the first- principles researches based on the density functional theory. Results show that the concentration of C-dopants may cause important influence on the magnetic and the electric properties of rocksalt MgS. C dopants are inclined to have a scattering distribution. MGC0.0625S0.9375^, aMgC0.1250S0.8750 and MgC0.1875S0.8125 have evident half-metallicity. They have wide spin energy gaps, thus high Curie temperature possibly. Their supercell magnetic moments are near to integral numbers 2.0, 4.0 and 6.0μB. The main reason for spin polarization and half-metallicity of C-doped MgS is that there are sp hybridized orbitals in ligand compound ML6 caused by covalent interaction between C-ions and Mg-ions.
基金supported by the National Natural Science Foundation of China(Grant No.61475192)the Science Research Program of National University of Defense Technology,China(Grant No.JC140702)
文摘A dip of the transverse component of the magnetic moment as a function of resonance frequency-detuning will emerge when the intensity of oscillating magnetic field exceeds a specific value, which is demonstrated theoretically and experimentally. The linewidth of magnetic-resonance signal can be much smaller than when the Mx–MR magnetometer operates on condition that the intensity of oscillating magnetic field is smaller than this specific value, and the Mx–MR magnetometer can possess a much higher signal-to-noise ratio. The experimental result shows that the sensitivity of Mx–MR magnetometer can be improved by an order of magnitude under this condition.
基金A.Laref was sponsored by the‘Research Center of Female Scientific and Medical Colleges’,Deanship of Scientific Research,King Saud University。
文摘By employing the spin resolved density functional theory, half-metallic character is investigated in Cs2NpBr6 having a K2PtCl6-type structure. The results precisely predict the half-metallic behavior of Cs2NpBr6. In spin-down state it presents an indirect band gap, while in spin-up channel it turns metallic. The structure optimization confirms the half-metallic nature in ferromagnetic configuration. The calculated magnetic moment is 3 μB toward which the main contributor is the Np atom.Furthermore, all the computed results are compared with the available experimental and theoretical values. According to the present analysis, we recommend Cs2NpBr6 for spintronic applications.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10847134 and 60471042)the Natural Science Foundation of Shandong Province, China (Grant No Y2005A05)
文摘The electronic structures and magnetic properties of SmCo7-xMx （M=Ti, Si, Zr, Hf, Cu, B, Ag, Ga, Mn） compounds are investigated by using a spin-polarized MS-Xα method. The results show that the long-range ferromagnetic order is determined by a stronger 3d-5d interaction, rather than the traditional RKKY interaction, and the effects of doping element M on 3d-5d coupling are negligible in Sm-Co-based compounds. The nonmagnetic dopant Si atoms have a larger effect on the moments of 2e site although they preferably occupy the Co 3g sites, which results in the stronger uniaxial anisotropy of this compound. Analysis of the formation energies indicates that 5d-element doped compounds are more stable than other dopants, and furthermore, they have a higher Curie temperature above room temperature, which will be in favor of their potential application as high-temperature permanent magnets.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10574036 and 10574037）. and the Hebei Natural Science Foundation （Grant Nos A2004000141 and 2005000143）.
文摘The structural stability and magnetic properties of the icosahedral Ni13, Ni13^＋1 and Ni13^-1 clusters have been obtained by utilizing all-electron density functional theory with the generalized gradient approximations for the exchange-correlation energy. The calculated results show that the ground states of neutral and charged clusters all favour a D3d structure, a distorted icosahedron, due to the Jahn-Teller effect. The radial distortions caused by doping one electron and by doping one hole are opposite to each other. Doping one electron will result in a 1/2 decrease and doping one hole will result in a 1/2 increase of the total spin. Both increasing interatomic spacing and decreasing coordination will lead to an enhancement of the spin magnetic moments for Nil3 clusters.
文摘Electronic and magnetic structures of zinc blende ZnO doped with V impurities are studied by first-principles calculations based on the Korringa-Kohn-Rostoker （KKR） method combined with the coherent potential approximation （CPA）. Calculations for the substitution of O by N or P are performed and the magnetic moment is found to be sensitive to the N or P content. Furthermore, the system exhibits a half-metallic band structure accompanied by the broadening of vanadium bands. The mechanism responsible for ferromagnetism is also discussed and the stability of the ferromagnetic state compared with that of the paramagnetic state is systematically investigated by calculating the total energy difference between them by using supercell method.
基金supported by the National Natural Science Foundation of China (Grant No. 10764003)
文摘Based on ab initio total energy calculations, the structural, electronic, mechanic, and magnetic properties of PdHx are investigated. It is found that bulk modulus of PdHx is larger than the metM Pd with the hydrogen storage except Pd4H2. The calculated results for the magnetic moments show that the hydrogen addition weakens the magnetic properties of the PdHx systems. A strong magneto-volume effect is found in PdHx structures as well as Pd. The transition from paramagnetism to ferromagnetism is discussed. The corresponding densities of states for both structures are also shown to understand the magnetic behaviour.
文摘Self-consistent ab initio calculations, based on the density functional theory （DFT） and using the full potential linear augmented plane wave （FLAPW） method, are performed to investigate both electronic and magnetic properties of the MnS layers. Polarized spin and spin-orbit coupling are included in the calculations within the framework of the antiferromagnetic state between two adjacent Mn layers. Magnetic moments considered to lie along axes are computed. Obtained data from ab initio calculations are used as input data for the high temperature series expansion （HTSE） calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the spin-4.39 nearest-neighbour Heisenberg model on centred face cubic （FCC） and lattices is thoroughly analysed by a power series coherent anomaly method （CAM）. The exchange interactions between the magnetic atoms, the N@el temperature, and the critical exponent associated with the magnetic susceptibility are obtained for the MnS layer.
基金Project supported by Chongqing Natural Science Foundation (Grant Nos. CSTC2007BB4391,CSTC2007BB2448,CSTC2007BB4385 and CSTC2008BB4083)Chongqing Science and Technology Foundation (Grant Nos. kj060515 andkj080518)
文摘s The geometrical structures of Cd0.75TM0.25Se （TM = Ti, V, Cr and Mn） are optimized, and then their electric and magnetic properties are investigated by performing first-principles calculations within the generalized gradient approximation for the exchange-correlation function based on density functional theory. Cd0.75TM0.25Se （TM =Ti and V） are found to have high spin-polarization near 100% at the Fermi level. Cd0.75TM0.25Se （TM = Cr and Mn） are half-metallic ferromagnets whose spin-polarization at the Fermi level is absolutely ＋100%. The supercell magnetic moments of Cd0.75Cr0.25Se and Cdo.75Mno.25Se are 4.00 and 5.00 μB, which arise mainly from Cr-ions and Mnions, respectively. The half-metallicity of Cdo.75Cro.25Se is more stable than that of Cd0.75Mn0.25Se. The electronic structures of Cr-ions and Mn-ions are Cr eg2↑t22g↑ and Mn e2 3 ↑t23g↑, respectively.
基金Project supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region,China(Grant Nos.2018D01C079 and 2018D01C072).
文摘The stable geometries,electronic structures,and magnetic behaviors of the ScLin(n=2-13)clusters are investigated by using particle swarm optimization(PSO)and density functional theory(DFT).The results show that these clusters have three-dimensional(3D)structures except ScLi2,and ScLi12,and ScLi13 that possess the cage-like structures.In analyses of the average binding energy,second-order difference of energy,and fragmentation energy,ScLi12 cluster is identified as magnetic superatom.The magnetic moment for each of these clusters owns an oscillating curve of different cluster sizes,and their magnetic moments are further investigated using molecular orbitals and jellium model.Of ScLin(n=2-13)clusters,ScLi12 has the largest spin magnetic moment(3µB),and molecular orbitals of ScLi12 can be described as 1S^21P^61D^5αD^2β.Additionally,Mulliken population and AdNDP bonding analysis are discussed and the results reveal that the Sc atom and Lin atoms make equal contribution to the total magnetic moment,and atomic charges transfer between Sc atoms and Li atoms.
文摘Electron magnetic circular dichroism opens a new door to explore magnetic properties by transmitted electrons in the transmission electron microscope. However, obtaining quantitative magnetic parameters, such as spin and orbital magnetic moment with element-specificity, goes a long way along with the development and improvement of this technique both in theoretical and experimental aspects. In this review, we will give a detailed description of the quantitative electron magnetic circular dichroism（EMCD） technique to measure magnetic parameters with spin-specificity, element-specificity,site-specificity, and orbital-spin-specificity. The discussion completely contains the procedures from raw experimental data acquisition to final magnetic parameters, together with the related custom code we have developed.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB606405)the CAEP Microsystem and THz Science and Technology Foundation,China(Grant No.CAEPMT201501)the Science Challenge Project,China(Grant No.JCKY2016212A503)
文摘Using the first-principles calculations, we study the structural, electronic, and magnetic properties of vanadium adsorbed MoSe_2 monolayer, and the magnetic couplings between the V adatoms at different adsorption concentrations. The calculations show that the V atom is chemically adsorbed on the MoSe_2 monolayer and prefers the location on the top of an Mo atom surrounded by three nearest-neighbor Se atoms. The interatomic electron transfer from the V to the nearestneighbor Se results in the polarized covalent bond with weak covalency, associated with the hybridizations of V with Se and Mo. The V adatom induces local impurity states in the middle of the band gap of pristine MoSe_2, and the peak of density of states right below the Fermi energy is associated with the V- dz^2 orbital. A single V adatom induces a magnetic moment of 5 μBthat mainly distributes on the V-3d and Mo-4d orbitals. The V adatom is in high-spin state, and its local magnetic moment is associated with the mid-gap impurity states that are mainly from the V-3d orbitals. In addition,the crystal field squashes a part of the V-4s electrons into the V-3d orbitals, which enhances the local magnetic moment.The magnetic ground states at different adsorption concentrations are calculated by generalized gradient approximations（GGA） and GGA＋U with enhanced electron localization. In addition, the exchange integrals between the nearest-neighbor V adatoms at different adsorption concentrations are calculated by fitting the first-principle total energies of ferromagnetic（FM） and antiferromagnetic（AFM） states to the Heisenberg model. The calculations with GGA show that there is a transition from ferromagnetic to antiferromagnetic ground state with increasing the distance between the V adatoms. We propose an exchange mechanism based on the on-site exchange on Mo and the hybridization between Mo and V, to explain the strong ferromagnetic coupling at a short distance between the V adatoms. However, the ferromagnetic exchange mechanism is sensitive to both the increased inter-adatom distance at low concentration and the enhanced electron localization by GGA＋U, which leads to antiferromagnetic ground state, where the antiferromagnetic superexchange is dominant.
