The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a...The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a charge ordering transition at TCO-257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below Too accompanied by an attenuation peak were observed. These features imply a strong electron phonom interaction via the Jahn-Teller effect iu the sample, Another broad attenuation peak was observed at around Tp-80 K. This anomaly is attributed to the phase separtion between the antiferromagnetic （AFM） and paramagnetic （PM） phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0.5Ca0.5MnO3 are both partially suppressed by replacing Mn with A1.展开更多
Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge orderi...Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge ordering phase of La0.4Ca0.6MnO3 was studied through the measurements of X-ray diffraction （XRD）, magnetization-temperature （M-T） curves and electron spin resonance （ESR） spectra. The experimental results indicate that the mother＇s body of La0.4Ca0.6MnO3 has very complicated magnetic structure, exhibits charge ordering phase at 258 K, and shows long-range strongly correlated charge ordering-antiferromagnetism （CO-AFM） phase from 175 to 50 K. Spin glass state appears when the temperature decreases to about 41 K. When the Cr substitution amount is x = 0.06, the charge ordering phase of the mother＇s body is de-stroyed, because the Cr3＋ substitution for Mn3＋ destroys the spin order of CE-type antiferromagnetism, and thus leads to the melting of charge ordering. It is verified experimentally that the strong coupling between charge order and spin order exists in the charge order system of CE-type antiferromagnetism.展开更多
The perovskite manganite sample La0.3Ca0.7Mn1-xWxO3 （x = 0.08, 0.12） was prepared by the solid-state reaction method. The effect of W doping on the Mn site to La0.3Ca0.7MnO3 charge ordering phase and the changing pr...The perovskite manganite sample La0.3Ca0.7Mn1-xWxO3 （x = 0.08, 0.12） was prepared by the solid-state reaction method. The effect of W doping on the Mn site to La0.3Ca0.7MnO3 charge ordering phase and the changing process of magnetic properties were studied through the measurement of the M-T curve, M-H curves, and ESR curves of the sample. The results showed that when x = 0.08, the charge ordering （CO） phase exists in the system, the transition temperature Tco= 275 K, and the system exhibits PM when T 〉 275 K. The system transforms from spin-disordering paramagnetism to spin-ordering antiferromagnetism in the charge ordering state with the temperature decreasing from 275 K to 230 K. The long-range antiferromagnetism forms and AFM/CO states coexist between 230 K and 5 K. There is a little ferromagnetic component in the AFM/CO background in a low temperature range. When x = 0.12, the CO phase in the system has almost melted completely. There is a little remnant of the CO phase below 150 K. The system exhibits paramagnetism when T 〉 150 K and transforms from paramagnetism to ferromagnetism when T〈 150 K.展开更多
The structure, transport, and magnetic properties of LaxBi0.5.xSr0.5MnO3 （LBSMO） （x=0.1 and 0.4） were studied through X-ray diffraction, magnetization, and electron spin resonance （ESR） measurements. The structu...The structure, transport, and magnetic properties of LaxBi0.5.xSr0.5MnO3 （LBSMO） （x=0.1 and 0.4） were studied through X-ray diffraction, magnetization, and electron spin resonance （ESR） measurements. The structural analysis showed that the LBSMO crystallized in an orthorhombic perovskite structure with Pbnm space group for x=-0.1 and Imma space group for x=0.4 and the highly polarizable 6s^2 lone pair of Bi^3＋ was the ttming factor for the structural variations. Magnetic studies revealed that the replacement of Bi ions by La ions resulted in the collapse high temperature charge ordering state of BSMO and it order Ferro Magnetically （FM） with Tc around 355 and 330 K for x=0.1 and 0.4, respectively. Both ESR, temperature and field dependant magnetization suggested that there was a coexistence of FM and the paramagnetic phases well below Tc and the FM and CO-AFM phases below 250 K of LBSMO.展开更多
Polycrystalline samples of La0.67-xPrxCa0.33MnO3(x=0～0.67) were synthesized by a conventional solid state reaction. X-ray diffraction revealed that the samples were all of single phase with an orthorhombic distorted ...Polycrystalline samples of La0.67-xPrxCa0.33MnO3(x=0～0.67) were synthesized by a conventional solid state reaction. X-ray diffraction revealed that the samples were all of single phase with an orthorhombic distorted perovskite structure. The magnetization depended on temperature measured in FC (field cooling) and ZFC (zero field cooling). It revealed that the compounds mainly underwent a ferromagnetic transition (TC) when the less Pr doped (x<0.4). With increasing doping content (x>0.5), the ferromagnetic transition disappeared and the antiferromagnetic transition (TN) was dominant. Charge ordering (TCO) also emerged when x>0.36. The transition temperatures TN and TCO would change with the Pr doping content. The phase separation could be used to explain these characters occurred in these polycrystalline samples.展开更多
The sample La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was prepared by the solid-state method. Magnetic properties of La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was studied through the measurement of M-T curve, M-H curves and ESR curves o...The sample La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was prepared by the solid-state method. Magnetic properties of La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was studied through the measurement of M-T curve, M-H curves and ESR curves of the sample. The results show that: charge ordering (CO) phase forms at 265 K; the system exhibits paramagnetism when T>265 K; it exhibits long-range anti-ferromagnetism (there is a little FM component in AFM background) and the coexistence of a little FM phase and AFM/CO phase forms when T<225 K; the system transforms from paramagnetism to antiferromagnetism in charge-ordering state with temperature decreasing from 265 to 225 K. The width of ESR spectrum line of the sample La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was measured, and the value of the line width of paramagnetic resonance ΔH_ PP increases with temperature decreasing, which indicates that ferromagnetic connection of the sample strengthens with temperature decreasing.展开更多
The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi0.4Ca0.6MnO3 film with a thickness of 110 nm at 103 K. Six different types of superla...The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi0.4Ca0.6MnO3 film with a thickness of 110 nm at 103 K. Six different types of superlattice structures are observed using the selected-area electron diffraction （SAED） technique, while three of them match well with the modulation stripes in high-resolution transmission electron microscopy （HRTEM） images. It is found that the modulation periodicity and direction are completely different in the region close to the Bi0.4Ca0.6MnO3/SrTiO3 interface from those in the region a little further from the Bi0.4Ca0.6MnO3/SrTiO3 interface, and the possible reasons for this are discussed. Based on the experimental results, structural models are proposed for these localized modulated structures.展开更多
The first-principles calculations were used to explore the tunable electronic structure in DyNiO_(3)(DNO)under the effects of the biaxial compressive and tensile strains.We explored how the biaxial strain tunes the or...The first-principles calculations were used to explore the tunable electronic structure in DyNiO_(3)(DNO)under the effects of the biaxial compressive and tensile strains.We explored how the biaxial strain tunes the orbital hybridization and influences the charge and orbital ordering states.We found that breathing mode and Jahn–Teller distortion play a primary role in charge ordering state and orbital ordering state,respectively.Additionally,the calculated results revealed that the biaxial strain has the ability to manipulate the phase competition between the two states.A phase transition point has been found under tensile train.If the biaxial train is larger than the point,the system favors orbital ordering state.If the strain is smaller than the point,the system is in charge ordering state favorably.展开更多
Subject Code:A04With the support by the National Natural Science Foundation of China,a collaborative study by the research groups led by Profs.Li Wei(李渭),Chen Xi(陈曦)and Xue Qikun(薛其坤)from Tsinghua University an...Subject Code:A04With the support by the National Natural Science Foundation of China,a collaborative study by the research groups led by Profs.Li Wei(李渭),Chen Xi(陈曦)and Xue Qikun(薛其坤)from Tsinghua University and Prof.Shen Zhixun(沈志勋)from Stanford University,demonstrates stripes developed展开更多
The alkali adatoms with controlled coverage on the surface have been demonstrated to effectively tune the surface band of quantum materials through in situ electron doping.However,the interplay of orderly arranged alk...The alkali adatoms with controlled coverage on the surface have been demonstrated to effectively tune the surface band of quantum materials through in situ electron doping.However,the interplay of orderly arranged alkali adatoms with the surface states of quantum materials remains unexplored.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we observed the emergent 3×3 super modulation of electronic states on the√3×√3R30°(R3)Cs ordered surface of kagome superconductor CsV_(3)Sb_(5).The nondispersive 3×3 superlattice at R3 ordered surface shows contrast inversion in positive and negative differential conductance maps,indicating a charge order origin.The 3×3 charge order is suppressed with increasing temperature and undetectable at a critical temperature of~62 K.Furthermore,in the Ta substituted sample CsV_(2.6)Ta_(0.4)Sb_(5),where long-range 2×2×2 charge density wave is significantly suppressed,the 3×3 charge order on the R3 ordered surface becomes blurred and much weaker than that in the undoped sample.It indicates that the 3×3 charge order on the R3 ordered surface is directly correlated to the bulk charge density waves in CsV_(3)Sb_(5).Our work provides a new platform for understanding and manipulating the cascade of charge orders in kagome superconductors.展开更多
In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction ...In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, wecalculate again its ground-state phase diagram at Glling x = 0.5 by the unrestricted real-spaceHartree-Fock approximation method. We find that, as the SSH electron-phonon interaction increases,the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomesmore stable. In other words, the charge order is much more fragile than the CE-type or theNeel-type antiferromagnetic orders under the electron-phonon perturbation. These results support theproposed theory in the recent publications that the charge order in these systems is induced by theantiferromagnetic correlations.展开更多
An oxide p-n heterojunction composed of Pro.6Ca0.4MnO3 film, with a charge order （CO） transition, and lwt% Nb- doped SrTiO3 substrate is fabricated, and the transport properties of the interface are experimentally s...An oxide p-n heterojunction composed of Pro.6Ca0.4MnO3 film, with a charge order （CO） transition, and lwt% Nb- doped SrTiO3 substrate is fabricated, and the transport properties of the interface are experimentally studied. The rectifying behavior of the junction, well described by the Newman equation, is observed, indicating that tunneling is the dominant process by which the carriers pass through the interface. Above and below the CO transition temperature, satisfactory linear dependencies of junction resistance on temperature are observed, but the slopes of the two resistance-temperature relations are different. The CO process is believed to be relevant to this difference.展开更多
The layered charges were calculated by means of constructing the complete structure of Tl Ba Ca Cu O superconductor. The weak link between Cu O and Ba O, or between Cu O and Tl O or Ba O or Tl O layers i...The layered charges were calculated by means of constructing the complete structure of Tl Ba Ca Cu O superconductor. The weak link between Cu O and Ba O, or between Cu O and Tl O or Ba O or Tl O layers is explained with the aid of the charge of limited layer unit calculated from the values of ions obtained, in addition to the possibility of forming charges fluctuation, which depends on the π coordination covalent bond on Cu O plane and O Tl O structure. The possible chemical tight bonding orbitals are in accordance with those of other superconductors obtained by quantum theoretical method, which occur at Cu 3d (x 2-y 2) and O 2p x,y . The valence band composed of Cu 3d and O 2p orbital energy levels is obviously an energy band of conduction. The ordered charge on layers is the main reason that raises T c of superconductors. The difference of electronic structure of ab plane and c axis leads to the anisotropy properties.展开更多
Aiming at the problem of increasing the peak-to-valley difference of grid load and the rising cost of user charging caused by the disorderly charging of large-scale electric vehicles,this paper proposes a coordinated ...Aiming at the problem of increasing the peak-to-valley difference of grid load and the rising cost of user charging caused by the disorderly charging of large-scale electric vehicles,this paper proposes a coordinated charging scheduling strategy for multiple types of electric vehicles based on the degree of urgency of vehicle use.First,considering the range loss characteristics,dynamic time-sharing tariff mechanism,and user incentive policy in the lowtemperature environment of northern winter,a differentiated charging model is constructed for four types of vehicles:family cars,official cars,buses,and cabs.Then,we innovatively introduce the urgency parameter of charging demand for multiple types of vehicles and dynamically divide the emergency and non-emergency charging modes according to the difference between the regular charging capacity and the user’s minimum power demand.When the conventional charging capacity is less than the minimum power demand of the vehicle within the specified time,it is the emergency vehicle demand,and this type of vehicle is immediately charged in fast charging mode after connecting to the grid.On the contrary,it is a non-emergency demand,and the vehicle is connected to the grid to choose the appropriate time to charge in conventional charging mode.Finally,by optimizing the objective function to minimize the peakto-valley difference between the grid and the vehicle owner’s charging cost,and designing the charging continuity constraints to avoid battery damage,it ensures that the vehicle is efficiently dispatched under the premise of meeting the minimum power demand.Simulation results show that the proposed charging strategy can reduce the charging cost of vehicle owners by 26.33%,reduce the peak-to-valley difference rate of the grid by 29.8%,and significantly alleviate the congestion problem during peak load hours,compared with the disordered charging mode,while ensuring that the electric vehicles are not overcharged and meet the electricity demand of vehicle owners.This paper solves the problems of the existing research on the singularity of vehicle models and the lack of environmental adaptability and provides both economic and practical solutions for the cooperative optimization of electric vehicles and power grids in multiple scenarios.展开更多
The polycrystalline samples of Pro.45（Ca1-xSrx）0.55MnO3 （x = 0.0, 0.2, 0.4, 0.6） were prepared by solid-state reaction. Influence of Sr2＋ substitution for Ca2＋ at A site on magnetism was studied through the meas...The polycrystalline samples of Pro.45（Ca1-xSrx）0.55MnO3 （x = 0.0, 0.2, 0.4, 0.6） were prepared by solid-state reaction. Influence of Sr2＋ substitution for Ca2＋ at A site on magnetism was studied through the measurements of X-ray diffraction （XRD） spectrum, the magnetization-temperature （M-T） curves and electron spin resonance （ESR） curves. The results show that the magnetism strengthens and charge ordering weakens gradually with the increase of Sr2＋ substitution amount, respectively. The transition of paramagnetism（PM）-antiferromagnetism（AFM） occurs below the transition temperature of charge ordering （Tco）, and there is tittle ferromagnetic phase in the antiferromagnetic background at the lower temperature, which results in complex magnetic phases of the samples. Ferromagnetic clusters appear and grow larger with the increase of substitution amount./n addition, the reentrant spin-glass behavior appears at about 41 K. The magnetism phenomenon of the samples is mainly due to the competition between double exchange and Jahn-Teller coupling. The Jahn-Teller coupling becomes weak, and the double exchange wins the advantage in the competition with the increase of substitution amount, which leads to the magnetism variation of the system.展开更多
Polycrystalline Nd0.75Na0.25Mn1-xCrxO3（0≤x≤0.1） samples were prepared by sol-gel method and their magnetic and electrical transport properties were investigated experimentally.The parent compound with x=0 was a ch...Polycrystalline Nd0.75Na0.25Mn1-xCrxO3（0≤x≤0.1） samples were prepared by sol-gel method and their magnetic and electrical transport properties were investigated experimentally.The parent compound with x=0 was a charge ordered manganite and the charge ordering transition occurred at 170 K.For lower Cr concentration（x0.03）,the samples preserved the charge ordering features of the parent compound,but the charge ordering transition temperature decreased with increasing x,in particular from 170 K for x=0 to 154 K for x=0.02.For the x≥0.03 samples,paramagnetic to ferromagnetic phase transition took place and the Curie temperature increased from 112.8 K for x=0.04 to 125.5 K for x=0.1.The electrical transport properties were also influenced by Cr doping.For x0.03,the samples displayed insulator characteristics below 300 K.For x=0.04,the sample showed insulator-metal transition around 75 K.For x≥0.05,the insulator-metal transition disappeared and the compounds showed insulator features again.The magnetic and electrical properties could be well explained by the phase separation scenario.展开更多
Metal-to-insulator transitions (MITs),which are achieved in 3d-band correlated transitional metal oxides,trigger abrupt variations in electrical,optical,and/or magnetic properties beyond those of conventional semicond...Metal-to-insulator transitions (MITs),which are achieved in 3d-band correlated transitional metal oxides,trigger abrupt variations in electrical,optical,and/or magnetic properties beyond those of conventional semiconductors.Among such material families,iron(Fe:3d^(6)4s^(2))-containing oxides pique interest owing to their widely tunable MIT properties,which are associated with the various valence states of Fe.Their potential electronic applications also show promise,given the large abundance of Fe on Earth.Representative MIT properties triggered by critical temperature (TMIT) were reported for ReFe_(2)O_(4)(Fe^(2.5+)),ReBaFe_(2)O_(5)(Fe^(2.5+)),Fe_(3)O_(4)(Fe^(2.67+)),Re_(1/3)Sr_(2/3)FeO_(3)(Fe^(3.67+)),Re Cu_(3)Fe_(4)O_(12)(Fe^(3.75+)),and Ca_(1-x)Sr_(x)FeO_(3)(Fe^(4+))(where Re represents rare-earth elements).The common feature of MITs of these Fe-containing oxides is that they are usually accompanied by charge ordering transitions or disproportionation associated with the valence states of Fe.Herein,we review the material family of Fe-containing MIT oxides,their MIT functionalities,and their respective mechanisms.From the perspective of potentially correlated electronic applications,the tunability of the TMITand its resultant resistive change in Fe-containing oxides are summarized and further compared with those of other materials exhibiting MIT functionality.In particular,we highlight the abrupt MIT and wide tunability of TMITof Fe-containing quadruple perovskites,such as Re Cu3Fe4O12.However,their effective material synthesis still needs to be further explored to cater to potential applications.展开更多
Measurements of crystal structures, electrical and magnetic properties for the electron doped BixCa1-xMnO3 （0〈x≤〈0.33） reveal the presence of a variety of notable changes in correlation with magnetic transitions ...Measurements of crystal structures, electrical and magnetic properties for the electron doped BixCa1-xMnO3 （0〈x≤〈0.33） reveal the presence of a variety of notable changes in correlation with magnetic transitions and charge ordering. Samples with x〈0.2 in general show a clear ferromagnetic transitions around 130 K. On the other hand, samples with 0.2≤x≤0.33 show much more complex low-temperature magnetic properties perhaps due to the coupling between the magnetic states and orbital/charge ordering. Structural transformations and structural modulations in the x=0.25 and 0.33 samples have been observed by transmission electron microscopy.展开更多
V-based kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)have attracted much attention due to their novel properties such as unconventional superconductivity,giant anomalous Hall effect,charge density wave(CDW)and pair density...V-based kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)have attracted much attention due to their novel properties such as unconventional superconductivity,giant anomalous Hall effect,charge density wave(CDW)and pair density wave.Except for the 2a_(0)×2a_(0)CDW(charge density wave with in-plane 2×2 superlattice modulation)in AV_(3)Sb_(5),an additional 1×4(4a_(0))unidirectional stripe order has been observed at the Sb surface of Rb V3 Sb5 and CsV_(3)Sb_(5).However,the stability and electronic nature of the 4a_(0) stripe order remain controversial and unclear.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we systematically study the 4a_(0) stripe order on the Sb-terminated surface of CsV_(3)Sb_(5).We find that the 4a_(0) stripe order is visible in a large energy range.The STM images with positive and negative bias show contrast inversion,which is the hallmark for the Peierls-type CDW.In addition,below the critical temperature about 60 K,the 4a_(0)stripe order keeps unaffected against the topmost Cs atoms,point defects,step edges and magnetic field up to 8 T.Our results provide experimental evidences on the existence of unidirectional CDW in CsV_(3)Sb_(5).展开更多
The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently d...The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.展开更多
基金supported by the National Natural Science Foundation of China(No.10274075)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20030358056).
文摘The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a charge ordering transition at TCO-257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below Too accompanied by an attenuation peak were observed. These features imply a strong electron phonom interaction via the Jahn-Teller effect iu the sample, Another broad attenuation peak was observed at around Tp-80 K. This anomaly is attributed to the phase separtion between the antiferromagnetic （AFM） and paramagnetic （PM） phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0.5Ca0.5MnO3 are both partially suppressed by replacing Mn with A1.
基金supported by the Key Program of the National Natural Science Foundation of China (No.19934003)the Key Program of Natural Science Research of Anhui Education Department (No.KJ2011A259+3 种基金 KJ2008A34ZC)the Natural Science Research Programs of Anhui Education Department, China (No.KJ2010B229No.KJ2010B228No.KJ2009B281Z)
文摘Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge ordering phase of La0.4Ca0.6MnO3 was studied through the measurements of X-ray diffraction （XRD）, magnetization-temperature （M-T） curves and electron spin resonance （ESR） spectra. The experimental results indicate that the mother＇s body of La0.4Ca0.6MnO3 has very complicated magnetic structure, exhibits charge ordering phase at 258 K, and shows long-range strongly correlated charge ordering-antiferromagnetism （CO-AFM） phase from 175 to 50 K. Spin glass state appears when the temperature decreases to about 41 K. When the Cr substitution amount is x = 0.06, the charge ordering phase of the mother＇s body is de-stroyed, because the Cr3＋ substitution for Mn3＋ destroys the spin order of CE-type antiferromagnetism, and thus leads to the melting of charge ordering. It is verified experimentally that the strong coupling between charge order and spin order exists in the charge order system of CE-type antiferromagnetism.
基金This project was financially supported by the National Natural Science Foundation Key Project of China (No. 19934003)the National Key Fundamental Research Project of China (No. 001CB610604)+1 种基金the Natural Science Research Project of the Education Department of Anhui Province (No. 2004KJ331)the Natural Science Research Project of Colleges and Universities of Anhui Province, China (No. 2005KJ234)
文摘The perovskite manganite sample La0.3Ca0.7Mn1-xWxO3 （x = 0.08, 0.12） was prepared by the solid-state reaction method. The effect of W doping on the Mn site to La0.3Ca0.7MnO3 charge ordering phase and the changing process of magnetic properties were studied through the measurement of the M-T curve, M-H curves, and ESR curves of the sample. The results showed that when x = 0.08, the charge ordering （CO） phase exists in the system, the transition temperature Tco= 275 K, and the system exhibits PM when T 〉 275 K. The system transforms from spin-disordering paramagnetism to spin-ordering antiferromagnetism in the charge ordering state with the temperature decreasing from 275 K to 230 K. The long-range antiferromagnetism forms and AFM/CO states coexist between 230 K and 5 K. There is a little ferromagnetic component in the AFM/CO background in a low temperature range. When x = 0.12, the CO phase in the system has almost melted completely. There is a little remnant of the CO phase below 150 K. The system exhibits paramagnetism when T 〉 150 K and transforms from paramagnetism to ferromagnetism when T〈 150 K.
基金the Ministry of Hunan Resources and Development (India)
文摘The structure, transport, and magnetic properties of LaxBi0.5.xSr0.5MnO3 （LBSMO） （x=0.1 and 0.4） were studied through X-ray diffraction, magnetization, and electron spin resonance （ESR） measurements. The structural analysis showed that the LBSMO crystallized in an orthorhombic perovskite structure with Pbnm space group for x=-0.1 and Imma space group for x=0.4 and the highly polarizable 6s^2 lone pair of Bi^3＋ was the ttming factor for the structural variations. Magnetic studies revealed that the replacement of Bi ions by La ions resulted in the collapse high temperature charge ordering state of BSMO and it order Ferro Magnetically （FM） with Tc around 355 and 330 K for x=0.1 and 0.4, respectively. Both ESR, temperature and field dependant magnetization suggested that there was a coexistence of FM and the paramagnetic phases well below Tc and the FM and CO-AFM phases below 250 K of LBSMO.
基金the Nature Science Foundation of Hebei Province (E2006000058)Doctor Foundation of Hebei Univ.Tech.
文摘Polycrystalline samples of La0.67-xPrxCa0.33MnO3(x=0～0.67) were synthesized by a conventional solid state reaction. X-ray diffraction revealed that the samples were all of single phase with an orthorhombic distorted perovskite structure. The magnetization depended on temperature measured in FC (field cooling) and ZFC (zero field cooling). It revealed that the compounds mainly underwent a ferromagnetic transition (TC) when the less Pr doped (x<0.4). With increasing doping content (x>0.5), the ferromagnetic transition disappeared and the antiferromagnetic transition (TN) was dominant. Charge ordering (TCO) also emerged when x>0.36. The transition temperatures TN and TCO would change with the Pr doping content. The phase separation could be used to explain these characters occurred in these polycrystalline samples.
文摘The sample La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was prepared by the solid-state method. Magnetic properties of La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was studied through the measurement of M-T curve, M-H curves and ESR curves of the sample. The results show that: charge ordering (CO) phase forms at 265 K; the system exhibits paramagnetism when T>265 K; it exhibits long-range anti-ferromagnetism (there is a little FM component in AFM background) and the coexistence of a little FM phase and AFM/CO phase forms when T<225 K; the system transforms from paramagnetism to antiferromagnetism in charge-ordering state with temperature decreasing from 265 to 225 K. The width of ESR spectrum line of the sample La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was measured, and the value of the line width of paramagnetic resonance ΔH_ PP increases with temperature decreasing, which indicates that ferromagnetic connection of the sample strengthens with temperature decreasing.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10974105 and 50832007)the Project of Introducing Talents to Support Thousand Talents Programs,China (Grant No. P201101032)+1 种基金the Program of Upgrading Technology for Scientific Instruments in Shandong Province,China (Grant No. 2011SJGZ16)the Program of Science and Technology in Qingdao City,China (Grant No. 11-2-4-23-hz)
文摘The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi0.4Ca0.6MnO3 film with a thickness of 110 nm at 103 K. Six different types of superlattice structures are observed using the selected-area electron diffraction （SAED） technique, while three of them match well with the modulation stripes in high-resolution transmission electron microscopy （HRTEM） images. It is found that the modulation periodicity and direction are completely different in the region close to the Bi0.4Ca0.6MnO3/SrTiO3 interface from those in the region a little further from the Bi0.4Ca0.6MnO3/SrTiO3 interface, and the possible reasons for this are discussed. Based on the experimental results, structural models are proposed for these localized modulated structures.
基金Project supported by the National Key Basic Research Program of China(Grant No.2019YFA0308500)the National Natural Science Foundation of China(Grant No.11721404)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB33030200).
文摘The first-principles calculations were used to explore the tunable electronic structure in DyNiO_(3)(DNO)under the effects of the biaxial compressive and tensile strains.We explored how the biaxial strain tunes the orbital hybridization and influences the charge and orbital ordering states.We found that breathing mode and Jahn–Teller distortion play a primary role in charge ordering state and orbital ordering state,respectively.Additionally,the calculated results revealed that the biaxial strain has the ability to manipulate the phase competition between the two states.A phase transition point has been found under tensile train.If the biaxial train is larger than the point,the system favors orbital ordering state.If the strain is smaller than the point,the system is in charge ordering state favorably.
文摘Subject Code:A04With the support by the National Natural Science Foundation of China,a collaborative study by the research groups led by Profs.Li Wei(李渭),Chen Xi(陈曦)and Xue Qikun(薛其坤)from Tsinghua University and Prof.Shen Zhixun(沈志勋)from Stanford University,demonstrates stripes developed
基金Project supported by the National Key Research and Development Project of China(Grant Nos.2022YFA1204100 and 2019YFA0308500)the National Natural Science Foundation of China(Grant No.62488201)+1 种基金the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-003)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘The alkali adatoms with controlled coverage on the surface have been demonstrated to effectively tune the surface band of quantum materials through in situ electron doping.However,the interplay of orderly arranged alkali adatoms with the surface states of quantum materials remains unexplored.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we observed the emergent 3×3 super modulation of electronic states on the√3×√3R30°(R3)Cs ordered surface of kagome superconductor CsV_(3)Sb_(5).The nondispersive 3×3 superlattice at R3 ordered surface shows contrast inversion in positive and negative differential conductance maps,indicating a charge order origin.The 3×3 charge order is suppressed with increasing temperature and undetectable at a critical temperature of~62 K.Furthermore,in the Ta substituted sample CsV_(2.6)Ta_(0.4)Sb_(5),where long-range 2×2×2 charge density wave is significantly suppressed,the 3×3 charge order on the R3 ordered surface becomes blurred and much weaker than that in the undoped sample.It indicates that the 3×3 charge order on the R3 ordered surface is directly correlated to the bulk charge density waves in CsV_(3)Sb_(5).Our work provides a new platform for understanding and manipulating the cascade of charge orders in kagome superconductors.
文摘In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, wecalculate again its ground-state phase diagram at Glling x = 0.5 by the unrestricted real-spaceHartree-Fock approximation method. We find that, as the SSH electron-phonon interaction increases,the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomesmore stable. In other words, the charge order is much more fragile than the CE-type or theNeel-type antiferromagnetic orders under the electron-phonon perturbation. These results support theproposed theory in the recent publications that the charge order in these systems is induced by theantiferromagnetic correlations.
基金Project supported by the National Natural Science Foundation of China(Grant No.10804089)
文摘An oxide p-n heterojunction composed of Pro.6Ca0.4MnO3 film, with a charge order （CO） transition, and lwt% Nb- doped SrTiO3 substrate is fabricated, and the transport properties of the interface are experimentally studied. The rectifying behavior of the junction, well described by the Newman equation, is observed, indicating that tunneling is the dominant process by which the carriers pass through the interface. Above and below the CO transition temperature, satisfactory linear dependencies of junction resistance on temperature are observed, but the slopes of the two resistance-temperature relations are different. The CO process is believed to be relevant to this difference.
文摘The layered charges were calculated by means of constructing the complete structure of Tl Ba Ca Cu O superconductor. The weak link between Cu O and Ba O, or between Cu O and Tl O or Ba O or Tl O layers is explained with the aid of the charge of limited layer unit calculated from the values of ions obtained, in addition to the possibility of forming charges fluctuation, which depends on the π coordination covalent bond on Cu O plane and O Tl O structure. The possible chemical tight bonding orbitals are in accordance with those of other superconductors obtained by quantum theoretical method, which occur at Cu 3d (x 2-y 2) and O 2p x,y . The valence band composed of Cu 3d and O 2p orbital energy levels is obviously an energy band of conduction. The ordered charge on layers is the main reason that raises T c of superconductors. The difference of electronic structure of ab plane and c axis leads to the anisotropy properties.
基金funded by Science and Technology Project of SGCC(SGJLCC00KJJS2203595).
文摘Aiming at the problem of increasing the peak-to-valley difference of grid load and the rising cost of user charging caused by the disorderly charging of large-scale electric vehicles,this paper proposes a coordinated charging scheduling strategy for multiple types of electric vehicles based on the degree of urgency of vehicle use.First,considering the range loss characteristics,dynamic time-sharing tariff mechanism,and user incentive policy in the lowtemperature environment of northern winter,a differentiated charging model is constructed for four types of vehicles:family cars,official cars,buses,and cabs.Then,we innovatively introduce the urgency parameter of charging demand for multiple types of vehicles and dynamically divide the emergency and non-emergency charging modes according to the difference between the regular charging capacity and the user’s minimum power demand.When the conventional charging capacity is less than the minimum power demand of the vehicle within the specified time,it is the emergency vehicle demand,and this type of vehicle is immediately charged in fast charging mode after connecting to the grid.On the contrary,it is a non-emergency demand,and the vehicle is connected to the grid to choose the appropriate time to charge in conventional charging mode.Finally,by optimizing the objective function to minimize the peakto-valley difference between the grid and the vehicle owner’s charging cost,and designing the charging continuity constraints to avoid battery damage,it ensures that the vehicle is efficiently dispatched under the premise of meeting the minimum power demand.Simulation results show that the proposed charging strategy can reduce the charging cost of vehicle owners by 26.33%,reduce the peak-to-valley difference rate of the grid by 29.8%,and significantly alleviate the congestion problem during peak load hours,compared with the disordered charging mode,while ensuring that the electric vehicles are not overcharged and meet the electricity demand of vehicle owners.This paper solves the problems of the existing research on the singularity of vehicle models and the lack of environmental adaptability and provides both economic and practical solutions for the cooperative optimization of electric vehicles and power grids in multiple scenarios.
基金financially supported by the National Natural Foundation of China (Grant No.19934003)the Natural Science Research Key Program of Anhui Educational Committee (KJ2011A259)the Cultivating Base of Anhui Key Laboratory of Spintronics and Nano-materials Research Program(No.2010YKF04)
文摘The polycrystalline samples of Pro.45（Ca1-xSrx）0.55MnO3 （x = 0.0, 0.2, 0.4, 0.6） were prepared by solid-state reaction. Influence of Sr2＋ substitution for Ca2＋ at A site on magnetism was studied through the measurements of X-ray diffraction （XRD） spectrum, the magnetization-temperature （M-T） curves and electron spin resonance （ESR） curves. The results show that the magnetism strengthens and charge ordering weakens gradually with the increase of Sr2＋ substitution amount, respectively. The transition of paramagnetism（PM）-antiferromagnetism（AFM） occurs below the transition temperature of charge ordering （Tco）, and there is tittle ferromagnetic phase in the antiferromagnetic background at the lower temperature, which results in complex magnetic phases of the samples. Ferromagnetic clusters appear and grow larger with the increase of substitution amount./n addition, the reentrant spin-glass behavior appears at about 41 K. The magnetism phenomenon of the samples is mainly due to the competition between double exchange and Jahn-Teller coupling. The Jahn-Teller coupling becomes weak, and the double exchange wins the advantage in the competition with the increase of substitution amount, which leads to the magnetism variation of the system.
基金supported by the Key Project of Chinese Ministry of Education(109042)Natural Science Foundation of Tianjin City(10JCYBJC02400)
文摘Polycrystalline Nd0.75Na0.25Mn1-xCrxO3（0≤x≤0.1） samples were prepared by sol-gel method and their magnetic and electrical transport properties were investigated experimentally.The parent compound with x=0 was a charge ordered manganite and the charge ordering transition occurred at 170 K.For lower Cr concentration（x0.03）,the samples preserved the charge ordering features of the parent compound,but the charge ordering transition temperature decreased with increasing x,in particular from 170 K for x=0 to 154 K for x=0.02.For the x≥0.03 samples,paramagnetic to ferromagnetic phase transition took place and the Curie temperature increased from 112.8 K for x=0.04 to 125.5 K for x=0.1.The electrical transport properties were also influenced by Cr doping.For x0.03,the samples displayed insulator characteristics below 300 K.For x=0.04,the sample showed insulator-metal transition around 75 K.For x≥0.05,the insulator-metal transition disappeared and the compounds showed insulator features again.The magnetic and electrical properties could be well explained by the phase separation scenario.
基金financially supported by the National Key Research and Development Program of China (No.2021YFA0718900)the National Natural Science Foundation of China (No.62074014)the Xiaomi Scholar project。
文摘Metal-to-insulator transitions (MITs),which are achieved in 3d-band correlated transitional metal oxides,trigger abrupt variations in electrical,optical,and/or magnetic properties beyond those of conventional semiconductors.Among such material families,iron(Fe:3d^(6)4s^(2))-containing oxides pique interest owing to their widely tunable MIT properties,which are associated with the various valence states of Fe.Their potential electronic applications also show promise,given the large abundance of Fe on Earth.Representative MIT properties triggered by critical temperature (TMIT) were reported for ReFe_(2)O_(4)(Fe^(2.5+)),ReBaFe_(2)O_(5)(Fe^(2.5+)),Fe_(3)O_(4)(Fe^(2.67+)),Re_(1/3)Sr_(2/3)FeO_(3)(Fe^(3.67+)),Re Cu_(3)Fe_(4)O_(12)(Fe^(3.75+)),and Ca_(1-x)Sr_(x)FeO_(3)(Fe^(4+))(where Re represents rare-earth elements).The common feature of MITs of these Fe-containing oxides is that they are usually accompanied by charge ordering transitions or disproportionation associated with the valence states of Fe.Herein,we review the material family of Fe-containing MIT oxides,their MIT functionalities,and their respective mechanisms.From the perspective of potentially correlated electronic applications,the tunability of the TMITand its resultant resistive change in Fe-containing oxides are summarized and further compared with those of other materials exhibiting MIT functionality.In particular,we highlight the abrupt MIT and wide tunability of TMITof Fe-containing quadruple perovskites,such as Re Cu3Fe4O12.However,their effective material synthesis still needs to be further explored to cater to potential applications.
基金the Outstanding Youth Fund(J.Q.Li)organized by the National Natural Science Foundation of China(No.10225415)the National Science Foundation of China(19804004)
文摘Measurements of crystal structures, electrical and magnetic properties for the electron doped BixCa1-xMnO3 （0〈x≤〈0.33） reveal the presence of a variety of notable changes in correlation with magnetic transitions and charge ordering. Samples with x〈0.2 in general show a clear ferromagnetic transitions around 130 K. On the other hand, samples with 0.2≤x≤0.33 show much more complex low-temperature magnetic properties perhaps due to the coupling between the magnetic states and orbital/charge ordering. Structural transformations and structural modulations in the x=0.25 and 0.33 samples have been observed by transmission electron microscopy.
基金financially supported by the National Key Research and Development Project of China(Grant Nos.2018YFA0305800 and 2019YFA0308500)the National Natural Science Foundation of China(Grant Nos.61888102and 52022105)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB30000000 and XDB28000000)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-003)the University of Chinese Academy of Sciences。
文摘V-based kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)have attracted much attention due to their novel properties such as unconventional superconductivity,giant anomalous Hall effect,charge density wave(CDW)and pair density wave.Except for the 2a_(0)×2a_(0)CDW(charge density wave with in-plane 2×2 superlattice modulation)in AV_(3)Sb_(5),an additional 1×4(4a_(0))unidirectional stripe order has been observed at the Sb surface of Rb V3 Sb5 and CsV_(3)Sb_(5).However,the stability and electronic nature of the 4a_(0) stripe order remain controversial and unclear.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we systematically study the 4a_(0) stripe order on the Sb-terminated surface of CsV_(3)Sb_(5).We find that the 4a_(0) stripe order is visible in a large energy range.The STM images with positive and negative bias show contrast inversion,which is the hallmark for the Peierls-type CDW.In addition,below the critical temperature about 60 K,the 4a_(0)stripe order keeps unaffected against the topmost Cs atoms,point defects,step edges and magnetic field up to 8 T.Our results provide experimental evidences on the existence of unidirectional CDW in CsV_(3)Sb_(5).
基金Project supported by the National Basic Research Program of China(Grant No.2014CB921500)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07030300)the National Natural Science Foundation of China(Grant No.11574378)
文摘The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.
