Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr_(2)IrO_(4). It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0....Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr_(2)IrO_(4). It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0.3 in Sr_(2-x)Pb_(x)IrO_(4). The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr_(2)IrO_(4) matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x=0.2.The present results give a fresh material base to explore new physics in doped Sr_(2)IrO_(4) systems.展开更多
The transport properties of La_(0.67)Sr_(0.33)Mn_(O3) (LSMO) epitaxial films on differently orientated LaAlO3 substrates have been studied. The as-deposited films with different orientation exhibit different transport...The transport properties of La_(0.67)Sr_(0.33)Mn_(O3) (LSMO) epitaxial films on differently orientated LaAlO3 substrates have been studied. The as-deposited films with different orientation exhibit different transport behaviours. The resistivity of the films on the (100) and (110) substrates undergoes a metal--insulator transition while the resistivity of the film on the (111) substrate is insulator-like. This is attributed to the discrepancy of oxygen deficiency in the samples which is influenced by the lattice mismatch between the film and the substrate. After being annealed at 700℃ in 1-atm flowing pure oxygen for half an hour, all films have the same resistivity behaviour as the bulk LSMO, which may be important for future applications.展开更多
Non-stoichiometry effect on the extreme magnetoresistance is systematically investigated for the Weyl semimetal WTe_2. Magnetoresistance and Hall resistivity are measured for the as-grown samples with a slight differe...Non-stoichiometry effect on the extreme magnetoresistance is systematically investigated for the Weyl semimetal WTe_2. Magnetoresistance and Hall resistivity are measured for the as-grown samples with a slight difference in Te vacancies and the annealed samples with increased Te vacancies. The fits to a two-band model show that the magnetoresistance is strongly dependent on the residual resistivity ratio(i.e., the degree of non-stoichiometry),which is eventually understood in terms of electron doping that not only breaks the balance between electron-type and hole-type carrier densities, but also reduces the average carrier mobility. Thus the compensation effect and ultrahigh mobility are probably the main driving force of the extreme magnetoresistance in WTe_2.展开更多
The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast s...The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast sharply with those previously reported for nematically ordered Fe Se by chemical-vapor-transport(CVT)growth.No signature of the electronic nematicity,but an evident metal-to-nonmetal crossover with increasing temperature,is detected in the normal state of the present hydrothermal samples.Interestingly,a higher superconducting critical temperature T_c of 13.2 K is observed compared to a suppressed T_c of 9 K in the presence of the nematicity in the CVT Fe Se.Moreover,the upper critical field in the zero-temperature limit is found to be isotropic with respect to the field direction and to reach a higher value of-42 T,which breaks the Pauli limit by a factor of 1.8.展开更多
HgCr_2S_4 is a typical compound manifesting competing ferromagnetic(FM) and antiferromagnetic(AFM) exchanges as well as strong spin-lattice coupling.Here we study these effects by intentionally choosing a combination ...HgCr_2S_4 is a typical compound manifesting competing ferromagnetic(FM) and antiferromagnetic(AFM) exchanges as well as strong spin-lattice coupling.Here we study these effects by intentionally choosing a combination of magnetization under external hydrostatic pressure and thermal conductivity at various magnetic fields.Upon applying pressure up to 10 kbar at 1kOe,while the magnitude of magnetization reduces progressively,the AFM ordering temperature T_N enhances concomitantly at a rate of about 1.5K/kbar.Strikingly,at 10 kOe the field polarized FM state is found to be driven readily back to an AFM one even at only 5 kbar.In addition,the thermal conductivity exhibits drastic increments at various fields in the temperature range with strong spin fluctuations,reaching about 30% at 50 kOe.Consequently,the results give new experimental evidence of spin-lattice coupling.Apart from the colossal magnetocapacitance and colossal magnetoresistance reported previously,the findings here may enable new promising functionalities for potential applications.展开更多
We measure the current–voltage(I–V)characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2with the superconducting transition temperature(TC)around 30.5 K,under a 10 T magnetic field applied perpendicular and ...We measure the current–voltage(I–V)characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2with the superconducting transition temperature(TC)around 30.5 K,under a 10 T magnetic field applied perpendicular and parallel to the ab plane.We find that the shapes of the I–V isotherms are very different from the description by the vortex-glass(VG)model.Combining theoretical calculations and analysis of theρH⊥ab–T andρH ab–T data,we give an explicit discussion over the suitability of the VG model for the A0.8Fe2Se2superconductors,and point out the possibility of the material acting as a convenient platform for re-examination and further study of the complex vortex behaviors in the layered superconductors.展开更多
The transition from vortex glass to a liquid phase is studied in Ba Ni0.1Fe1.9As2 single crystal with Tc = 19.4 K by magneto-resistance measurements. The resistivity curves are measured in magnetic fields in a range o...The transition from vortex glass to a liquid phase is studied in Ba Ni0.1Fe1.9As2 single crystal with Tc = 19.4 K by magneto-resistance measurements. The resistivity curves are measured in magnetic fields in a range of 0 T–13 T for H c and H⊥c. Good scalings for all values of resistivity ρ(H, T) and the effective pinning potential U0(H, T) are obtained with the modified vortex glass theory by using the critical exponents s and H0. Phase diagrams for H c and H⊥c are determined based on the obtained vortex glass temperature Tg, the vortex dimensionality crossover temperature T*, and the upper critical magnetic field Hc2. Our results suggest that both below and above 5 T, single vortex pinning co-exists with collective creep, and collective creep is dominant. There is a narrower vortex liquid region for H⊥c than for H c in the vortex phase diagram, which may originate from a stronger pinning force.展开更多
Since high magnetic field(MF) intensity can improve the image quality and reduce magnetic resonance imaging(MRI) acquisition time, the field intensity of MRIs has continued to increase over the past few decades. Altho...Since high magnetic field(MF) intensity can improve the image quality and reduce magnetic resonance imaging(MRI) acquisition time, the field intensity of MRIs has continued to increase over the past few decades. Although MRIs in most current hospitals are 0.5 T–3 T, there are preclinical studies have been carried out using 9.4 T MRI, and engineers are also putting efforts on building MRIs with even higher MFs. However, the accompanied safety issue of high-field MRIs is an emergent question to address before their clinical applications. In the meantime, the static magnetic field(SMF) has been shown to inhibit tumor growth in previous studies. Here, we investigated both the safety issue and the anti-tumor potentials of 3.7 T–24.5 T SMFs on GIST-T1 gastrointestinal stromal tumor-bearing nude mice. We followed up the mice three weeks after their exposure to high SMF and found that none of the mice died or had severe organ damage, except for slightly decreased food intake, weight gain, and liver function. Moreover, the tumor growth was inhibited by 3.7 T–24.5 T SMFs(up to ～54%). It is interesting that the effects are more dependent on MF gradient than intensities, and for the same gradient and intensity, mice responded differently to hypogravity and hypergravity conditions. Therefore, our study not only demonstrated the safeness of high SMFs up to 24.5 T on mice but also revealed their anti-tumor potentials in the future.展开更多
The binary pnictide semimetals have attracted considerable attention due to their fantastic physical properties that include topological effects, negative magnetoresistance, Weyl fermions, and large non-saturation mag...The binary pnictide semimetals have attracted considerable attention due to their fantastic physical properties that include topological effects, negative magnetoresistance, Weyl fermions, and large non-saturation magnetoresistance. In this paper, we have successfully grown the high-quality V_(1-δ)Sb_(2) single crystals by Sb flux method and investigated their electronic transport properties. A large positive magnetoresistance that reaches 477% under a magnetic field of 12 T at T = 1.8 K was observed. Notably, the magnetoresistance showed a cusp-like feature at the low magnetic fields and such feature weakened gradually as the temperature increased, which indicated the presence of a weak antilocalization effect(WAL). In addition, based upon the experimental and theoretical band structure calculations, V_(1-δ)Sb_(2) is a research candidate for a flat band.展开更多
We report our nuclear magnetic resonance(NMR) study on the structurally spin chain compound Ni_(2)NbBO_(6) with complex magnetic coupling.The antiferromagnetic transition is monitored by the line splitting resulting f...We report our nuclear magnetic resonance(NMR) study on the structurally spin chain compound Ni_(2)NbBO_(6) with complex magnetic coupling.The antiferromagnetic transition is monitored by the line splitting resulting from the staggered internal hyperfine field.The magnetic coupling configuration proposed by the first-principle density functional theory(DFT) is supported by NMR spectral analysis.For the spin dynamics,a prominent peak at T~35 K well above the Neel temperature(T_(N)~20 K at μ0 H=10 T) is observed from the spin-lattice relaxation data.As compared with the dc-susceptibility,this behavior indicates an antiferromagnetic coupling with the typical energy scale of ~3 meV.Thus,the Ni_(2)NbBO_(6) compound can be viewed as strongly ferromagnetically coupled armchair spin chains along the crystalline b-axis.These facts place strong constraints on the theoretical model for this compound.展开更多
High-quality epitaxial LaRhO3(LRO) thin films on SrTiO3(110) single-crystalline substrates are fabricated by pulsed laser deposition and their photoconductivity properties are studied. The transient photoconductivity(...High-quality epitaxial LaRhO3(LRO) thin films on SrTiO3(110) single-crystalline substrates are fabricated by pulsed laser deposition and their photoconductivity properties are studied. The transient photoconductivity(TPC) effect is found in this semiconductor LRO film at room temperature. The magnitude of TPC increases almost linearly with the laser power intensities and the photon energies in visible light range. Moreover, the difference in the TPC results under two airflow conditions confirms that both intrinsic photoinduced carrier accumulation and extrinsic photoinduced heating effects contribute to the magnitude of TPC effect.展开更多
基金Project supported by the National Key R&D Program of China (Grant Nos.2022YFA1403203 and 2021YFA1600201)the National Natural Science Foundation of China (Grant Nos.11974356 and 12274414)+1 种基金the Joint Funds of the National Natural Science Foundation of Chinathe Chinese Academy of Sciences Large-Scale Scientific Facility (Grant No.U1932216)。
文摘Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr_(2)IrO_(4). It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0.3 in Sr_(2-x)Pb_(x)IrO_(4). The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr_(2)IrO_(4) matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x=0.2.The present results give a fresh material base to explore new physics in doped Sr_(2)IrO_(4) systems.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10504029 and 10334090, and the State Key Project of Fundamental Research of China under Grant No 001CB610604.
基金Supported by the National Natural Science Foundation of China under Grant No.19934003the Research Fund for the Doctoral Program of Higher Education and the Chinese Academy of Sciences.
文摘The transport properties of La_(0.67)Sr_(0.33)Mn_(O3) (LSMO) epitaxial films on differently orientated LaAlO3 substrates have been studied. The as-deposited films with different orientation exhibit different transport behaviours. The resistivity of the films on the (100) and (110) substrates undergoes a metal--insulator transition while the resistivity of the film on the (111) substrate is insulator-like. This is attributed to the discrepancy of oxygen deficiency in the samples which is influenced by the lattice mismatch between the film and the substrate. After being annealed at 700℃ in 1-atm flowing pure oxygen for half an hour, all films have the same resistivity behaviour as the bulk LSMO, which may be important for future applications.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10504029 and 10334090）, and the State Key Project of Fundamental Research, China （Grant No 001CB610604）.
基金Supported by the National Key R&D Program of China under Grant Nos 2016YFA0300404 and 2017YFA0403600the National Natural Science Foundation of China under Grant Nos 51603207,U1532267,11574288 and 11674327the Natural Science Foundation of Anhui Province under Grant No 1708085MA08
文摘Non-stoichiometry effect on the extreme magnetoresistance is systematically investigated for the Weyl semimetal WTe_2. Magnetoresistance and Hall resistivity are measured for the as-grown samples with a slight difference in Te vacancies and the annealed samples with increased Te vacancies. The fits to a two-band model show that the magnetoresistance is strongly dependent on the residual resistivity ratio(i.e., the degree of non-stoichiometry),which is eventually understood in terms of electron doping that not only breaks the balance between electron-type and hole-type carrier densities, but also reduces the average carrier mobility. Thus the compensation effect and ultrahigh mobility are probably the main driving force of the extreme magnetoresistance in WTe_2.
基金Supported by the National Key Research and Development Program of China (Grant Nos.2016YFA0300300 and 2017YFA0303003)the National Natural Science Foundation of China (Grant Nos.12061131005,11834016 and 11888101)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No.XDB25000000)the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant Nos.QYZDY-SSW-SLH001)。
文摘The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast sharply with those previously reported for nematically ordered Fe Se by chemical-vapor-transport(CVT)growth.No signature of the electronic nematicity,but an evident metal-to-nonmetal crossover with increasing temperature,is detected in the normal state of the present hydrothermal samples.Interestingly,a higher superconducting critical temperature T_c of 13.2 K is observed compared to a suppressed T_c of 9 K in the presence of the nematicity in the CVT Fe Se.Moreover,the upper critical field in the zero-temperature limit is found to be isotropic with respect to the field direction and to reach a higher value of-42 T,which breaks the Pauli limit by a factor of 1.8.
基金Supported by the National Natural Science Foundation of China under Grant Nos U1332143 and 11574323
文摘HgCr_2S_4 is a typical compound manifesting competing ferromagnetic(FM) and antiferromagnetic(AFM) exchanges as well as strong spin-lattice coupling.Here we study these effects by intentionally choosing a combination of magnetization under external hydrostatic pressure and thermal conductivity at various magnetic fields.Upon applying pressure up to 10 kbar at 1kOe,while the magnitude of magnetization reduces progressively,the AFM ordering temperature T_N enhances concomitantly at a rate of about 1.5K/kbar.Strikingly,at 10 kOe the field polarized FM state is found to be driven readily back to an AFM one even at only 5 kbar.In addition,the thermal conductivity exhibits drastic increments at various fields in the temperature range with strong spin fluctuations,reaching about 30% at 50 kOe.Consequently,the results give new experimental evidence of spin-lattice coupling.Apart from the colossal magnetocapacitance and colossal magnetoresistance reported previously,the findings here may enable new promising functionalities for potential applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404002,11404003,and 11074001)the Scientific Research Foundation for the Returned Overseas Chinese Scholarsthe"211 Project"of Anhui University,China(Grant No.J01001319-J10113190007)
文摘We measure the current–voltage(I–V)characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2with the superconducting transition temperature(TC)around 30.5 K,under a 10 T magnetic field applied perpendicular and parallel to the ab plane.We find that the shapes of the I–V isotherms are very different from the description by the vortex-glass(VG)model.Combining theoretical calculations and analysis of theρH⊥ab–T andρH ab–T data,we give an explicit discussion over the suitability of the VG model for the A0.8Fe2Se2superconductors,and point out the possibility of the material acting as a convenient platform for re-examination and further study of the complex vortex behaviors in the layered superconductors.
基金Project supported by the Foundation of Henan Educational Committee,China(Grant No.13B140951)the Foundation of Henan University of Technology,China(Grant Nos.11JCYJ15 and 2011BS030)
文摘The transition from vortex glass to a liquid phase is studied in Ba Ni0.1Fe1.9As2 single crystal with Tc = 19.4 K by magneto-resistance measurements. The resistivity curves are measured in magnetic fields in a range of 0 T–13 T for H c and H⊥c. Good scalings for all values of resistivity ρ(H, T) and the effective pinning potential U0(H, T) are obtained with the modified vortex glass theory by using the critical exponents s and H0. Phase diagrams for H c and H⊥c are determined based on the obtained vortex glass temperature Tg, the vortex dimensionality crossover temperature T*, and the upper critical magnetic field Hc2. Our results suggest that both below and above 5 T, single vortex pinning co-exists with collective creep, and collective creep is dominant. There is a narrower vortex liquid region for H⊥c than for H c in the vortex phase diagram, which may originate from a stronger pinning force.
基金Project supported by the National Key R&D Program of China(Grant Nos.2016YFA0400900 and 2017YFA0402903)the National Natural Science Foundation of China(Grant Nos.U1532151 and 51627901)+2 种基金the Major/Innovative Program of Development Foundation of Hefei Center for Physical Science,Technology(Grant No.2016FXCX004)Hefei Science Center,CAS(Grant No.2016HSC-IU007)the CASHIPS Director’s Fund(Grant No.YZJJ201704)to Qingyou Lu and Xin Zhang
文摘Since high magnetic field(MF) intensity can improve the image quality and reduce magnetic resonance imaging(MRI) acquisition time, the field intensity of MRIs has continued to increase over the past few decades. Although MRIs in most current hospitals are 0.5 T–3 T, there are preclinical studies have been carried out using 9.4 T MRI, and engineers are also putting efforts on building MRIs with even higher MFs. However, the accompanied safety issue of high-field MRIs is an emergent question to address before their clinical applications. In the meantime, the static magnetic field(SMF) has been shown to inhibit tumor growth in previous studies. Here, we investigated both the safety issue and the anti-tumor potentials of 3.7 T–24.5 T SMFs on GIST-T1 gastrointestinal stromal tumor-bearing nude mice. We followed up the mice three weeks after their exposure to high SMF and found that none of the mice died or had severe organ damage, except for slightly decreased food intake, weight gain, and liver function. Moreover, the tumor growth was inhibited by 3.7 T–24.5 T SMFs(up to ～54%). It is interesting that the effects are more dependent on MF gradient than intensities, and for the same gradient and intensity, mice responded differently to hypogravity and hypergravity conditions. Therefore, our study not only demonstrated the safeness of high SMFs up to 24.5 T on mice but also revealed their anti-tumor potentials in the future.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. U2032214, U2032163, and 11904002)the Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2017483)the Natural Science Foundation of Anhui Province, China (Grant No. 1908085QA15)。
文摘The binary pnictide semimetals have attracted considerable attention due to their fantastic physical properties that include topological effects, negative magnetoresistance, Weyl fermions, and large non-saturation magnetoresistance. In this paper, we have successfully grown the high-quality V_(1-δ)Sb_(2) single crystals by Sb flux method and investigated their electronic transport properties. A large positive magnetoresistance that reaches 477% under a magnetic field of 12 T at T = 1.8 K was observed. Notably, the magnetoresistance showed a cusp-like feature at the low magnetic fields and such feature weakened gradually as the temperature increased, which indicated the presence of a weak antilocalization effect(WAL). In addition, based upon the experimental and theoretical band structure calculations, V_(1-δ)Sb_(2) is a research candidate for a flat band.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0401802)the National Natural Science Foundation of China(Grant Nos.11874057,11504377,11574288,11874158,U1732273,and 21927814)+1 种基金the Users with Excellence Program of Hefei Science Center CAS(Grant No.2019HSC-UE008)supported by the High Magnetic Field Laboratory of Anhui Province。
文摘We report our nuclear magnetic resonance(NMR) study on the structurally spin chain compound Ni_(2)NbBO_(6) with complex magnetic coupling.The antiferromagnetic transition is monitored by the line splitting resulting from the staggered internal hyperfine field.The magnetic coupling configuration proposed by the first-principle density functional theory(DFT) is supported by NMR spectral analysis.For the spin dynamics,a prominent peak at T~35 K well above the Neel temperature(T_(N)~20 K at μ0 H=10 T) is observed from the spin-lattice relaxation data.As compared with the dc-susceptibility,this behavior indicates an antiferromagnetic coupling with the typical energy scale of ~3 meV.Thus,the Ni_(2)NbBO_(6) compound can be viewed as strongly ferromagnetically coupled armchair spin chains along the crystalline b-axis.These facts place strong constraints on the theoretical model for this compound.
基金Supported by the National Key R&D Program of China under Grant Nos 2017YFA0303603 and 2016YFA0401803the National Natural Science Foundation of China under Grant Nos 11574316,U1532155,61805256 and U1832106the Key Research Program of Frontier Sciences of CAS under Grant No QYZDB-SSW-SLH011
文摘High-quality epitaxial LaRhO3(LRO) thin films on SrTiO3(110) single-crystalline substrates are fabricated by pulsed laser deposition and their photoconductivity properties are studied. The transient photoconductivity(TPC) effect is found in this semiconductor LRO film at room temperature. The magnitude of TPC increases almost linearly with the laser power intensities and the photon energies in visible light range. Moreover, the difference in the TPC results under two airflow conditions confirms that both intrinsic photoinduced carrier accumulation and extrinsic photoinduced heating effects contribute to the magnitude of TPC effect.
