Current and displacement stiffness are important parameters of axial magnetic bearing(AMB)and are usually considered as constants for the control system.However,in actual dynamic work situations,time-varying force lea...Current and displacement stiffness are important parameters of axial magnetic bearing(AMB)and are usually considered as constants for the control system.However,in actual dynamic work situations,time-varying force leads to time-varying currents and air gap with a specific frequency,which makes the stiffness of appear decrease and even worsens control performance for the whole system.In this paper,an AMB dynamic stiffness model considering the flux variation across the air gap due to frequency is established to obtain the accurate dynamic stiffness.The dynamic stiffness characteristics are analyzed by means of the dynamic equivalent magnetic circuit method.The analytical results show that the amplitude of current and displacement stiffness decreases with frequency increasing.Moreover,compared with the stiffness model without considering the variation of flux density across the air gap,the improved dynamic stiffness results are closer to the actual results.Through the dynamic stiffness measurement method of AMB,experiments of AMB in magnetically suspended molecular pump(MSMP)are carried out and the experimental results are consistent with theoretical analysis results.This paper proposes the dynamic stiffness model of axial magnetic bearing considering the variation of flux density across the air gap,which improves the accuracy of the AMB stiffness analysis.展开更多
We study the coutrol of gate voltage over the magnetization of a single-molecule magnet (SMM) weakly coupled to a ferromagnetic and a normal metal electrode in the presence of the temperature gradient between two el...We study the coutrol of gate voltage over the magnetization of a single-molecule magnet (SMM) weakly coupled to a ferromagnetic and a normal metal electrode in the presence of the temperature gradient between two electrodes. It is demonstrated that the SMM's magnetization can change periodically with periodic gate voltage due to the driving oI the temperature gradient. Under an appropriate matching of the electrode polarization, the temperature difference and the pulse width of gate voltage, the SMM's magnetization can be completely reversed in a period of gate voltage. The corresponding flipping time can be controlled by the system parameters. In addition, we also investigate the tunneling anisotropic magnetoresistance (TAMFt) of the device in the steady state when the ferromagnetic electrode is noncollinear with the easy axis of the SMM, and show the jump characteristic of the TAMR.展开更多
Owing to the bistable character of the single molecular magnet (SMM), it can generate 100% spin-polarized currents even connected with normal (N) leads. In this work, we study the phonon-assisted spin current in N...Owing to the bistable character of the single molecular magnet (SMM), it can generate 100% spin-polarized currents even connected with normal (N) leads. In this work, we study the phonon-assisted spin current in N- SMM-N systems. We mainly focus on the interplay of SMM's bistable character and electron-phonon coupling. It is found that when SMM is trapped in one of the lowest bistable states, it can generate phonon-assisted spin- polarized currents. At the up-spin transport channel, it is accompanied by a phonon-assisted up-spin current, while at the down-spin transport channel, it is accompanied by a phonon-assisted down-spin current.展开更多
One novel oxamido-bridged trinuclear complex [Cu(CuL)2(ClO4)2] has been syn-thesized and structurally determined.It crystallizes in the monoclinic system,space group P21/n with a = 10.636(4),b = 11.645(4),c = ...One novel oxamido-bridged trinuclear complex [Cu(CuL)2(ClO4)2] has been syn-thesized and structurally determined.It crystallizes in the monoclinic system,space group P21/n with a = 10.636(4),b = 11.645(4),c = 16.038(6) ,β = 91.029(5)°,V = 1986.2(12) 3,C38H32Cl2Cu3N8O12,Mr = 1054.24,Dc = 1.763 Mg/m3,μ(MoKα) = 1.802 mm-1,F(000) = 1066,Z = 2,the final R = 0.0328 and wR = 0.0882 for 3152 observed reflections.The crystal structure is a trinuclear complex in which the CuII ions are bridged by macrocyclic oxamide groups.C-H···O hydrogen bonding interactions link the trinuclear fragment to form a 2D supramolecular architecture.Magnetic measurements indicate that the compound is moderately antiferromagnetically coupled.展开更多
We have studied the quantum fluctuations of inelastic spin-electron scattering in quantum dot with an embedded biaxial single molecule-magnet and particularly investigated the zero-frequency shot noise and Fano factor...We have studied the quantum fluctuations of inelastic spin-electron scattering in quantum dot with an embedded biaxial single molecule-magnet and particularly investigated the zero-frequency shot noise and Fano factor in different magnetic fields. It is found that the shot noise and Fano factor exhibit a stepwise behaviour as bias increases in the presence of interaction between the electron and molecule-magnet for a weak magnetic field. As magnetic field becomes strong, a dip is displayed in the shot-noise-bias curve due to the suppression of inelastic shot noise caused by the quantum tunneling of magnetisation. Because of the spontaneous inelastic tunneling at zero bias, a small shot noise occurs, which results in the case of Fano factor F ≥ 1. Moreover, our results show that the sweeping speed can also influence the shot noise and Fano factor obviously.展开更多
This paper numerically investigates the magnetoelastic instability in the S = 1/2 {XXZ} rings containing finite spins N with antiferromagnetic nearest-neighbour ({NN}) and next-nearest neighbour ({NNN}) coupling. ...This paper numerically investigates the magnetoelastic instability in the S = 1/2 {XXZ} rings containing finite spins N with antiferromagnetic nearest-neighbour ({NN}) and next-nearest neighbour ({NNN}) coupling. It finds that, as the {NN} anisotropy Δ1 equals the {NNN} anisotropy /varDelta2, there exists a critical {NNN} coupling strength J2c(≈0.5), at which the systems always locate in dimerized phase for arbitrary large spring constant. As Δ1 /ne Δ2, the values of J2^{/rm c} are dependent on N and the difference of (Δ1-/varDelta2).展开更多
A single-molecule magnet (SMM) coupled to two normal metallic electrodes can both switch spin-up and spin- down electronic currents within two different windows of SMM gate voltage. Such spin current switching in th...A single-molecule magnet (SMM) coupled to two normal metallic electrodes can both switch spin-up and spin- down electronic currents within two different windows of SMM gate voltage. Such spin current switching in the SMM tunnel junction arises from spin-selected single electron resonant tunneling via the lowest unoccupied molecular orbit of the SMM. Since it is not magnetically controlled but all-electrically controlled, the proposed spin current switching effect may have potential applications in future spintronics.展开更多
We use non-equilibrium Green's function method to analyze the shot noise spectrum of artificial single molecular magnets(ASMM) model in the strong spin–orbit coupling limit in sequential tunneling regime, mainly f...We use non-equilibrium Green's function method to analyze the shot noise spectrum of artificial single molecular magnets(ASMM) model in the strong spin–orbit coupling limit in sequential tunneling regime, mainly focusing on the effects of local large spin. In the linear response regime, the shot noise shows 2S + 1 peaks and is strongly spin-dependent.In the nonlinear response regime, one can observe 2S + 1 steps in shot noise and Fano factor. In these steps one can see the significant enhancement effect due to the spin-dependent multi-channel process of local large spin, which reduces electron correlations.展开更多
Coordination complex of a copper cyanurate(Cu(Ⅱ)-CA) was transformed into coordination polymers upon the stimulus of extra Cu(Ⅱ) through “directed Ostwald ripening”. By increasing the molar ratio of Cu(Ⅱ) to CA, ...Coordination complex of a copper cyanurate(Cu(Ⅱ)-CA) was transformed into coordination polymers upon the stimulus of extra Cu(Ⅱ) through “directed Ostwald ripening”. By increasing the molar ratio of Cu(Ⅱ) to CA, we obtained two coordination polymers with selective coordination sites: Cu(Ⅱ)-κ N(HCA)κ NCu(Ⅱ) and Cu(Ⅱ)-κ N(HCA)κ O-Cu(Ⅱ), which display disparate magnetic interactions.展开更多
Metal clusters with photoswitching ligands can undergo magnetic changes under light radiation,which makes them potential optical-response magnetic-switching materials.Herein,a photoswitchable Mn-oxo cluster[Mn^(II)_(1...Metal clusters with photoswitching ligands can undergo magnetic changes under light radiation,which makes them potential optical-response magnetic-switching materials.Herein,a photoswitchable Mn-oxo cluster[Mn^(II)_(15)Mn^(III)_(4)(L)_(18)(OH)_(12)(N_(3))_(6)](ClO_(4))_(2)(C_(6)H_(5)CN)_(8),(Mn19azo,HL=1-(hydroxymethyl)-3,5-dimethyl-4-(phenyldiazenyl)-pyrazole)has been designed and synthesized to realize the photoswitching behavior.Mn19azo shows quick trans-to-cis transformation upon 365 nm light irradiation in CH2Cl2 solution and solid state as confirmed by UV-Vis spectra.After the powder sample was irradiated for 80 min,the Curie constant of Mn19azo increases by about 7%.The change of magnetic properties can be considered as the result of the change of intermolecular interactions.展开更多
A new material for both magnetic coupling and electrocatalytic hydrogen generation based on a copper complex,[(HL)CuCl-CuCl(HL)]HCl 1 is prepared by the reaction of 2-(pyridylmethyl)amino-N,N-bis(2-methylene-4,...A new material for both magnetic coupling and electrocatalytic hydrogen generation based on a copper complex,[(HL)CuCl-CuCl(HL)]HCl 1 is prepared by the reaction of 2-(pyridylmethyl)amino-N,N-bis(2-methylene-4,6-difluorophenol)(H2L) and CuCl2·2H2O.In solid,complex 1 is built from two copper units([(HL)CuCl]),and exhibits an antiferromagnetic exchange interaction between copper(Ⅱ) ions(J=-160cm^-1).In liquid,1 can electrocatalyze hydrogen generation both from acetic acid with a turnover frequency(TOF) of 16.3 moles of hydrogen per mole of catalyst per hour at an overpotential(OP)of 941.6 mV(in DMF),and a neutral buffer with a TOF of 1415.6 moles of hydrogen per mole of catalyst per hour at an OP of 787.6 mV.展开更多
There is a small fraction of fast-relaxation species in Mn12-acetate, which is utilized to determine the dipolar field of Mn12. Here we report an easier way to precisely obtain the dipolar field by measuring the M-H c...There is a small fraction of fast-relaxation species in Mn12-acetate, which is utilized to determine the dipolar field of Mn12. Here we report an easier way to precisely obtain the dipolar field by measuring the M-H curves above the blocking temperature of fastrelaxation species. We found that there is a simple linear relationship between the magnetic moment and dipolar field; besides the dipolar field is also dependent on the sample shape, which is consistent with the numerical calculation.展开更多
Background The hairpin cell-penetrating peptides (hCPPs) demonstrate an interesting characteristic of conditioned activation by molecules. We hypothesized that hCPPs have the potential to selectively deliver a param...Background The hairpin cell-penetrating peptides (hCPPs) demonstrate an interesting characteristic of conditioned activation by molecules. We hypothesized that hCPPs have the potential to selectively deliver a paramagnetic gadolinium probe into the matrix metalloproteinase 2 (MMP-2) positive human ovary adenocarcinoma cell lines, SKOV-3. Methods hCPPs were synthesized and labeled with 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid gadolinium (111) (Gd-DOTA) and fluorescein isothiocyanate (FITC) by f-moc strategy using a standard solid phase peptide synthesis protocol. MMP-2 expression and activity were demonstrated by reverse transcriptase polymerase chain reaction (RT-PCR) and zymography. Internalization and location of hCPPs in SKOV-3 cells were observed by fluorescein imaging and flow cytometery. Selective delivery of Gd-DOTA in SKOV-3 cells was observed by magnetic resonance imaging (MRI) and transmission electron microscopy (TEM). Results The uptake of hCPPs by SKOV-3 cells depended on the activity of MMP-2. T1WI signals of SKOV-3 cells treated with Gd-DOTA-hCPPs suggested the uptake of Gd-DOTA-hCPPs increased in a time- (r=0.990, P 〈0.01) and concentration-dependent manner (r=0.964, P 〈0.001), but was inhibited by a MMP-2 inhibitor. Electron-dense particles observed in the cytoplasm and nucleus by transmission electron microscopy proved the intracellular penetration of gadolinium. Conclusions hCPPs can be used as an effective vector for an MRI molecular probe to assess the activity of MMP-2.展开更多
基金Excellent Youth Science Foundation of China(Grant No.51722501)National Natural Science Foundation of China(Grant No.51575025)+1 种基金National Natural Science Foundation of China-Youth Science Foundation(Grant No.61603052)Opening Foundation of State Key Laboratory of Advanced Welding and Joining(Grant No.AWJ-20-R02).
文摘Current and displacement stiffness are important parameters of axial magnetic bearing(AMB)and are usually considered as constants for the control system.However,in actual dynamic work situations,time-varying force leads to time-varying currents and air gap with a specific frequency,which makes the stiffness of appear decrease and even worsens control performance for the whole system.In this paper,an AMB dynamic stiffness model considering the flux variation across the air gap due to frequency is established to obtain the accurate dynamic stiffness.The dynamic stiffness characteristics are analyzed by means of the dynamic equivalent magnetic circuit method.The analytical results show that the amplitude of current and displacement stiffness decreases with frequency increasing.Moreover,compared with the stiffness model without considering the variation of flux density across the air gap,the improved dynamic stiffness results are closer to the actual results.Through the dynamic stiffness measurement method of AMB,experiments of AMB in magnetically suspended molecular pump(MSMP)are carried out and the experimental results are consistent with theoretical analysis results.This paper proposes the dynamic stiffness model of axial magnetic bearing considering the variation of flux density across the air gap,which improves the accuracy of the AMB stiffness analysis.
基金Supported by the National Natural Science Foundation of China under Grant No 11274208
文摘We study the coutrol of gate voltage over the magnetization of a single-molecule magnet (SMM) weakly coupled to a ferromagnetic and a normal metal electrode in the presence of the temperature gradient between two electrodes. It is demonstrated that the SMM's magnetization can change periodically with periodic gate voltage due to the driving oI the temperature gradient. Under an appropriate matching of the electrode polarization, the temperature difference and the pulse width of gate voltage, the SMM's magnetization can be completely reversed in a period of gate voltage. The corresponding flipping time can be controlled by the system parameters. In addition, we also investigate the tunneling anisotropic magnetoresistance (TAMFt) of the device in the steady state when the ferromagnetic electrode is noncollinear with the easy axis of the SMM, and show the jump characteristic of the TAMR.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11504210,11504211,11504212,11274207,11274208,11174115 and 11325417the Key Program of the Ministry of Education of China under Grant No 212018+2 种基金Shanxi Provincial Scientific and Technological Project(2015031002-2)Shanxi Provincial Natural Science Foundation under Grant Nos2013011007-2 and 2013021010-5Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province
文摘Owing to the bistable character of the single molecular magnet (SMM), it can generate 100% spin-polarized currents even connected with normal (N) leads. In this work, we study the phonon-assisted spin current in N- SMM-N systems. We mainly focus on the interplay of SMM's bistable character and electron-phonon coupling. It is found that when SMM is trapped in one of the lowest bistable states, it can generate phonon-assisted spin- polarized currents. At the up-spin transport channel, it is accompanied by a phonon-assisted up-spin current, while at the down-spin transport channel, it is accompanied by a phonon-assisted down-spin current.
基金supported by the National Natural Science Foundation of China (No.20771083 and 20901059)
文摘One novel oxamido-bridged trinuclear complex [Cu(CuL)2(ClO4)2] has been syn-thesized and structurally determined.It crystallizes in the monoclinic system,space group P21/n with a = 10.636(4),b = 11.645(4),c = 16.038(6) ,β = 91.029(5)°,V = 1986.2(12) 3,C38H32Cl2Cu3N8O12,Mr = 1054.24,Dc = 1.763 Mg/m3,μ(MoKα) = 1.802 mm-1,F(000) = 1066,Z = 2,the final R = 0.0328 and wR = 0.0882 for 3152 observed reflections.The crystal structure is a trinuclear complex in which the CuII ions are bridged by macrocyclic oxamide groups.C-H···O hydrogen bonding interactions link the trinuclear fragment to form a 2D supramolecular architecture.Magnetic measurements indicate that the compound is moderately antiferromagnetically coupled.
文摘We have studied the quantum fluctuations of inelastic spin-electron scattering in quantum dot with an embedded biaxial single molecule-magnet and particularly investigated the zero-frequency shot noise and Fano factor in different magnetic fields. It is found that the shot noise and Fano factor exhibit a stepwise behaviour as bias increases in the presence of interaction between the electron and molecule-magnet for a weak magnetic field. As magnetic field becomes strong, a dip is displayed in the shot-noise-bias curve due to the suppression of inelastic shot noise caused by the quantum tunneling of magnetisation. Because of the spontaneous inelastic tunneling at zero bias, a small shot noise occurs, which results in the case of Fano factor F ≥ 1. Moreover, our results show that the sweeping speed can also influence the shot noise and Fano factor obviously.
文摘This paper numerically investigates the magnetoelastic instability in the S = 1/2 {XXZ} rings containing finite spins N with antiferromagnetic nearest-neighbour ({NN}) and next-nearest neighbour ({NNN}) coupling. It finds that, as the {NN} anisotropy Δ1 equals the {NNN} anisotropy /varDelta2, there exists a critical {NNN} coupling strength J2c(≈0.5), at which the systems always locate in dimerized phase for arbitrary large spring constant. As Δ1 /ne Δ2, the values of J2^{/rm c} are dependent on N and the difference of (Δ1-/varDelta2).
基金supported by the National Natural Science Foundation of China (Grant Nos. 60825402,60421003,11074111 and 10974058)the State Key Program for Basic Research of China (Grant Nos. 2011CB922103,2009CB929504 and 2011CBA00205)
文摘A single-molecule magnet (SMM) coupled to two normal metallic electrodes can both switch spin-up and spin- down electronic currents within two different windows of SMM gate voltage. Such spin current switching in the SMM tunnel junction arises from spin-selected single electron resonant tunneling via the lowest unoccupied molecular orbit of the SMM. Since it is not magnetically controlled but all-electrically controlled, the proposed spin current switching effect may have potential applications in future spintronics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.1150421011504211+11 种基金11504212112742071127420811174115and11325417)the Key Program of the Ministry of Education of China(Grant No.212018)the Scientific and Technological Project of Shanxi ProvinceChina(Grant No.2015031002-2)the Natural Science Foundation of Shanxi ProvinceChina(Grant Nos.2013011007-2 and 2013021010-5) the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi ProvinceChina
文摘We use non-equilibrium Green's function method to analyze the shot noise spectrum of artificial single molecular magnets(ASMM) model in the strong spin–orbit coupling limit in sequential tunneling regime, mainly focusing on the effects of local large spin. In the linear response regime, the shot noise shows 2S + 1 peaks and is strongly spin-dependent.In the nonlinear response regime, one can observe 2S + 1 steps in shot noise and Fano factor. In these steps one can see the significant enhancement effect due to the spin-dependent multi-channel process of local large spin, which reduces electron correlations.
基金the financial support from the Australian Research Council (No.DP190101607)National Natural Science Foundation of China (No.21971203)。
文摘Coordination complex of a copper cyanurate(Cu(Ⅱ)-CA) was transformed into coordination polymers upon the stimulus of extra Cu(Ⅱ) through “directed Ostwald ripening”. By increasing the molar ratio of Cu(Ⅱ) to CA, we obtained two coordination polymers with selective coordination sites: Cu(Ⅱ)-κ N(HCA)κ NCu(Ⅱ) and Cu(Ⅱ)-κ N(HCA)κ O-Cu(Ⅱ), which display disparate magnetic interactions.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52261135637,22171164)the Natural Science Foundation of Shandong Province(No.ZR2022QB191)+2 种基金the Taishan Scholar Project of Shandong Province of China(Nos.tsqn201812003 and ts20190908)the Instrument Improvement Funds of Shandong University Public Technology Platform(No.ts20220102)the Slovenian Research Agency(Grant No.P2-0348).
文摘Metal clusters with photoswitching ligands can undergo magnetic changes under light radiation,which makes them potential optical-response magnetic-switching materials.Herein,a photoswitchable Mn-oxo cluster[Mn^(II)_(15)Mn^(III)_(4)(L)_(18)(OH)_(12)(N_(3))_(6)](ClO_(4))_(2)(C_(6)H_(5)CN)_(8),(Mn19azo,HL=1-(hydroxymethyl)-3,5-dimethyl-4-(phenyldiazenyl)-pyrazole)has been designed and synthesized to realize the photoswitching behavior.Mn19azo shows quick trans-to-cis transformation upon 365 nm light irradiation in CH2Cl2 solution and solid state as confirmed by UV-Vis spectra.After the powder sample was irradiated for 80 min,the Curie constant of Mn19azo increases by about 7%.The change of magnetic properties can be considered as the result of the change of intermolecular interactions.
基金supported by the National Natural Science Foundation of China (Nos. 20971045, 21271073)
文摘A new material for both magnetic coupling and electrocatalytic hydrogen generation based on a copper complex,[(HL)CuCl-CuCl(HL)]HCl 1 is prepared by the reaction of 2-(pyridylmethyl)amino-N,N-bis(2-methylene-4,6-difluorophenol)(H2L) and CuCl2·2H2O.In solid,complex 1 is built from two copper units([(HL)CuCl]),and exhibits an antiferromagnetic exchange interaction between copper(Ⅱ) ions(J=-160cm^-1).In liquid,1 can electrocatalyze hydrogen generation both from acetic acid with a turnover frequency(TOF) of 16.3 moles of hydrogen per mole of catalyst per hour at an overpotential(OP)of 941.6 mV(in DMF),and a neutral buffer with a TOF of 1415.6 moles of hydrogen per mole of catalyst per hour at an OP of 787.6 mV.
基金supported by the National Basic Research Program of China(Grant No. 2006CB921304)
文摘There is a small fraction of fast-relaxation species in Mn12-acetate, which is utilized to determine the dipolar field of Mn12. Here we report an easier way to precisely obtain the dipolar field by measuring the M-H curves above the blocking temperature of fastrelaxation species. We found that there is a simple linear relationship between the magnetic moment and dipolar field; besides the dipolar field is also dependent on the sample shape, which is consistent with the numerical calculation.
基金This work was supported by National Natural Science Foundation of China (No. 30770619, 30900364) and Beijing Municipal Commission of Education Research Foundation (No. KM200910025017).
文摘Background The hairpin cell-penetrating peptides (hCPPs) demonstrate an interesting characteristic of conditioned activation by molecules. We hypothesized that hCPPs have the potential to selectively deliver a paramagnetic gadolinium probe into the matrix metalloproteinase 2 (MMP-2) positive human ovary adenocarcinoma cell lines, SKOV-3. Methods hCPPs were synthesized and labeled with 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid gadolinium (111) (Gd-DOTA) and fluorescein isothiocyanate (FITC) by f-moc strategy using a standard solid phase peptide synthesis protocol. MMP-2 expression and activity were demonstrated by reverse transcriptase polymerase chain reaction (RT-PCR) and zymography. Internalization and location of hCPPs in SKOV-3 cells were observed by fluorescein imaging and flow cytometery. Selective delivery of Gd-DOTA in SKOV-3 cells was observed by magnetic resonance imaging (MRI) and transmission electron microscopy (TEM). Results The uptake of hCPPs by SKOV-3 cells depended on the activity of MMP-2. T1WI signals of SKOV-3 cells treated with Gd-DOTA-hCPPs suggested the uptake of Gd-DOTA-hCPPs increased in a time- (r=0.990, P 〈0.01) and concentration-dependent manner (r=0.964, P 〈0.001), but was inhibited by a MMP-2 inhibitor. Electron-dense particles observed in the cytoplasm and nucleus by transmission electron microscopy proved the intracellular penetration of gadolinium. Conclusions hCPPs can be used as an effective vector for an MRI molecular probe to assess the activity of MMP-2.