Hole density dependent magnetic structure and anisotropy in Fe-pnictide superconductor

The competition between different magnetic structures in hole-doped Fe-pnicitides is explored based on an extended five-orbital Hubbard model including long-range Coulomb interactions.Our results show that the stabilized magnetic structure evolves with increasing hole doping level.Namely,the stripe antiferromagnetic phase dominates at zero doping,while magnetic structures with more antiferromagnetic linking numbers such as the staggered tetramer,staggered trimer,and staggered dimer phases become energetically favorable as the hole density increases.At a certain doping level,energy degeneracy of different magnetic structures appears,indicating strong magnetic frustration and magnetic fluctuations in the system.We suggest that the magnetic competition induced by the hole doping may explain the fast decrease of the Neel temperature TNand the moderately suppressed magnetic moment in the hole doped Fe-pnicitides.Moreover,our results show a sign reversal of the kinetic energy anisotropy as the magnetic ground state evolves,which may be the mechanism behind the puzzling sign reversal of the in-plane resistivity anisotropy in hole-doped Fe-pnicitides.

The 3D magnetic structure beneath the continental margin of the northeastern South China Sea

Understanding the continental margin of the Northeastern South China Sea is critical to the study of deep structures, tectonic evolution, and dynamics of the region. One set of important data for this endeavor is the total-field magnetic data. Given the challenges associated with the magnetic data at low latitudes and with remanent magnetism in this area, we combine the equivalent-source technique and magnetic amplitude inversion to recover 3D subsurface magnetic structures. The inversion results show that this area is characterized by a north-south block division and east-west zonation. Magnetic regions strike in EW, NE and NW direction and are consistent with major tectonic trends in the region. The highly magnetic zone recovered from inversion in the continental margin differs visibly from that of the magnetically quiet zones to the south. The magnetic anomaly zone strikes in NE direction, covering an area of about 500 km × 60 km, and extending downward to a depth of 25 km or more. In combination with other geophysical data, we suggest that this strongly magnetic zone was produced by deep underplating of magma associated with plate subduction in Mesozoic period. The magnetically quiet zone in the south is an EW trending unit underlain by broad and gentle magnetic layers of lower crust. Its magnetic structure bears a clear resemblance to oceanic crust, assumed to be related to the presence of ancient oceanic crust there.

Magnetic Structure of Archean Kongling Group from Yangtze Craton,South China

Densities and various magnetic parameters (susceptibility, saturation magnetization, saturation isothermal remanent magnetization and intrinsic coercivity) were measured for 20 representative rock samples of different lithologies from the Archean Kongling amphibolite to granulite facies terrain of the Yangtze craton. Metasedimentary rocks and tonalitic trondhjemitic granodioritic granitic (TTGG) gneisses show that values of susceptibility κ and saturation isothermal remanent magnetization SIRM are higher than those of amphibolites and gabbros. The felsic gneisses have averages of κ =(1 163±375)×10 -6 SI, SIRM =(18.23±8.38) A/m and R 1=0.083 3± 0.005 7 and the metasedimentary rocks κ =(1 236±823)×10 -6 SI, SIRM =(20.70±10.91) A/m and R I=0.071 4±0.025 2. In contrast, mafic rocks have average κ =(764±316)×10 -6 SI, SIRM = (10.46±3.94)A/m and R 1=0.036±0.009 4, and are dominated by a mixed paramagnetic and ferrimagnetic behavior. Thermal magnetic analyses indicate that magnetite and maghemite of low coercivity are the major carriers of remanent magnetism in the metaclastic sedimentary rocks and TTGG gneisses. The amphibolite and gabbro contain minor amounts of magnetite and pyrrhotite. Magnetism of metaclastic sedimentary rocks and TTGG gneisses is highly heterogeneous; variation coefficients of κ and SIRM are as high as 67 % and 53 % for the former and 32 % and 46 % for the latter. Mineral compositions suggest that biotite may be responsible for the higher magnetism of the metasedimentary rocks. The highest variations in κ, SIRM and R I exhibited by metasedimentary rocks can also be interpreted by their largest absolute variations in biotite mass fraction relative to mafic rocks and felsic gneisses. The average ratio ( Q ) of natural remanent magnetization to induced magnetization of felsic gneisses and metasediments is 0.47 . Ratios ( REM ) of natural remanent to saturation isothermal remanent magnetization ranges between 0.000 001 and 0.027 000 and averages 0.002 540. These values are comparable to those of rocks of similar lithologies from the Archean Taihua high grade terrain of the North China craton and from the Ivrea zone, northern Italy. The dominant phase of magnetism carried by the Kongling rocks is suggested to be thermal remanent magnetization. Consequently, high temperature metamorphism exceeding the Curie point of magnetite (585 ℃) might be responsible for the formation of rock magnetism of the exposed crust in the area of investigation.

Influence of Zinc Doping upon Magnetic Structure of LaMnO_3 System

M-T curves, M-H curves and electron spin resonance (ESR) curves of LaMn_(1-x)Zn_xO_3(x=0.05, 0.10, (0.20,) 0.30, 0.40) were studied. Experimental results indicate that: with increasing Zn doping, the T_C value decreases monotonously, and the system undergoes a transition from long-range ferromagnetic order to cluster-spin glass stated. The results are attributed to double exchange interaction, magnetic dilution and lattice effects by Zn doping.

Mechanical Analysis and Measurements of a Multicomponent NbTi/Cu Superconducting Magnets Structure for the Fully Superconducting Electron Cyclotron Resonance Ion Source

A fully superconducting electron cyclotron resonance （ECR） ion source （SECRAL ID is currently being built in the Institute of Modern Physics, Chinese Academy of Sciences. Its key components are three superconducting solenoids （Nb-Ti/Cu） and six superconducting sextupoles （Nb-Ti/Cu）. Different from the conventional supercon- ducting ECR magnetic structure, the SEC17AL Ⅱ includes three superconducting solenoid coils＇ that are located inside the superconducting sextupoles. The SECRAL Ⅱ can significantly reduce the interaction forces between the sextupole and the solenoids, and the magnets can also be more compact in size. For this multi-component SECRAL Ⅱ generating its self field of -8 T and being often exposed to the high self field, the mechanical analysis has become the main issue to keep their stress at 〈200 MPa on coils. The analytical and experimental results in mechanics are presented in the SECRAL Ⅱ structure. To improve the accuracy and efficiency of analysis, according to the composite rule of micromechanics, the equivalent uniform windings are used to simulate the epoxy-impregnated Nb-Ti/Cu coils. In addition, using low temperature strain gauges and a wireless fast strain acquisition system, a fundamental experiment on the based on our analysis, the stresses and deformations optimized. strains developments of a sextupole is reported. Finally, for its assembly of each SECRAL Ⅱ coil will be further

Synthesis,Structure,and Property of a Three-dimensional Channel Quaternary Compound:Cs_(0.75(6))Er_(4.43(5))In_(3.32(6))S_(12)

A new quaternary rare-earth sulfide, Cs0.75（6）Er443（5）In3.32（6）S12 （1）, is discovered by high temperature solid state reactions with a slight excess of CsCI flux. The structure is characterized by single-crystal X-ray diffraction data, while crystallizes in hexagonal space group P63/m （No. 176） with a = 12.0329（6）, c = 3.8693（5）A, V= 485.18（7） A3, Z = 1, Mr = 1606.57, Dc = 5.499 g/cm3,μ = 25.457 mm-1, F（000） = 752, the final R = 0.0337 and wR = 0.0904 for 328 observed reflections with I 〉 2σ（I）. Its structure features a three-dimensional framework with hexagonal channels that are centered by Cs cations. Such channels are formed by double chains of edge-sharing M（1）S6 （M（1） = Er（1）/In（1）） octahedra and single chains of Er（2）S6 triprism interconnected by corner-sharing. The syntheses, single-crystal analyses, optical band gap and magnetic property are reported.

Evolution of magnetic domain structure of martensite in Ni–Mn–Ga films under the interplay of the temperature and magnetic field

Ferromagnetic shape memory Ni-Mn-Ga films with 7M modulated structure were prepared on MgO （001） substrates by magnetron sputtering. Magnetization process with a typical two-hysteresis loop indicates the occurrence of the reversible magnetic field-induced reorientation. Magnetic domain structure and twin structure of the film were controlled by the in- terplay of the magnetic and temperature field. With cooling under an out-of-plane magnetic field, the evolution of magnetic domain structure reveals that martensitic transformation could be divided into two periods： nucleation and growth. With an in-plane magnetic field applied to a thermomagnetic-treated film, the evolution of magnetic domain structure gives evidence of a reorientation of twin variants of martensite. A microstructural model is described to define the twin structure and to produce the magnetic domain structure at the beginning of martensitic transformation; based on this model, the relationship between the twin structure and the magnetic domain structure for the treated film under an in-plane field is also described.

Crystal Structure and Magnetic Properties of a Dinuclear Terbium Compound Tb_2(μ_2-anthc)_4(anthc)_2(1,10-phen)_2

A dinuclear Tb（Ⅲ） compound, Tb_2（μ_2-anthc）_4（anthc）_2（1,10-phen）_2（1, Hanthc = 9-anthracenecarboxylic acid and 1,10-phen = 1,10-phenanthroline）, was synthesized under solvothermal condition and structurally characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the triclinic system, space group P1, with a = 12.5061（12）, b = 13.3168（10）, c = 15.0079（12） ？, α = 110.620（7）, β = 102.941（7）, γ = 107.036（7）o, V = 2081.8（3） ？~3, Z = 1, C_（114）H_（70）N_4O_（12）Tb_2, M_r = 2005.58, D_c = 1.600 g/cm^3, μ = 1.759 mm^（-1）, F（000） = 1008, the final R = 0.0294 and w R = 0.0608 for 8900 observed reflections with I 〉 2s（I）. In compound 1, two Tb（Ⅲ） ions are linked by four carboxylate groups of the bridging anthc– ligands to give a dinuclear Tb_2（μ_2-anthc）_4 unit wherein each Tb（III） ion is further capped by a terminal anthc– ligand and a 1,10-phen ligand in a chelating fashion. Detailed direct-current and alternating-current susceptibility measurements showed no slow magnetism relaxation phenomenon was observed for 1.

Synthesis,Crystal Structure and Magnetic Property of Ternary Neodymium Zirconium Sulfide,Nd2ZrS5

A new ternary neodymium zirconium sulfide Nd_2ZrS_5 was synthesized by high-temperature solid-state reaction and structurally characterized by single-crystal X-ray diffraction. It crystallizes in the orthorhombic space group Pnma（No. 62） belonging to the Y_2HfS_5 structure-type with a = 11.461（4）, b = 8.009（3）, c = 7.315（3） A, Z = 2 and V = 671.5（4）A3. Its structure features NdS_8 and ZrS_7 polyhedra-constructed a 3-D network. The data of magnetic susceptibility indicate its antiferromagnetic-like behavior without magnetic order down to 2 K.

Syntheses,Crystal Structures and Characterization of Two Coordination Polymers Based on Mixed Ligands

Two new coordination polymers,namely,{[Cd（1.5）（bc）2（HL）]（13）H2O}（2n）（1） and [Mn（ip）（H2L）（H2O）]n（2）（H2L = 3-（1 H-pyrazol-4-yl）-5-（pyridin-2-yl）-1,2,4-triazole,Hbc = benzoic acid,H2 ip = isophthalic acid） were constructed by solvothermal reaction.The compounds were characterized by elemental analysis,FT-IR spectroscopy,and single-crystal X-ray diffraction.Compound 1 displays a two-dimensional plane structure consisting of [Cd3（bc）2（HL）] subunits.Compound 2 possesses a one-dimensional chain structure and is further extended into a 3-D supramolecular architecture via hydrogen bonds.Moreover,photoluminescence studies showed compound 1 exhibits luminescent emissions with emission maxima at 375 nm.Magnetic susceptibility measurements of 2 indicate that domain antiferromagnetic interactions exist between Mn（Ⅱ） ions.In addition,thermogravimetric properties of 1 and 2 were also measured.

Structure and Magnetic Properties of Fe_(76.5)Si_(13.5)B_9Cu_1 Alloy with Nanoscale Grain Size

The structure and magnetic properties of Fe76.5Si13.5B9Cu1 alloys with a nanocrystalline (NC) bcc Fe(Si) phase trom about 23 to 46 nm in diameter, which were first formed into amorphous ribbons and then annealed at various temperatures between 703 and 773 K, have been investigated. At annealing temperatures from 703 to 748 K, the single NC bcc(Si) phase is obtained in the crystallized alloys. The grain size and the Si-content in the NC bcc Fe(Si) phase for the alloys annealed at different temperatures are presented. The soft magnetic properties and the saturation magnetostriction for the alloys with the NC bcc Fe(Si) phase are also measured. The results show that, the saturation magnetizotion and the permeability are improved for the alloys with only the NC bcc Fe(Si) phase and become better with decreasing of the NC bcc phase size, and the saturation magnetostriction declines for the alloys with increasing Si-content in the NC bcc Fe(Si) phase.

A Dinuclear Dysprosium-2-quinolinecarboxylate-1,10-Phenanthroline Compound:Crystal Structure and Magnetism

A dinuclear dysprosium（III） compound,[Dy2（μ2-OH）2（QLC）4（1,10-phen）2]·4H2O（1）（QLC-= 2-quinolinecarboxylate and 1,10-phen = 1,10-phenanthroline）,was synthesized and structurally and magnetically characterized.Compound 1 crystallizes in triclinic system,space group P1 with a = 10.9439（3）,b = 11.2823（3）,c = 12.2323（4） ？,α = 107.446（3）,β = 91.700（3）,γ = 91.511（2）°,V = 1439.25（8） A3,Z = 1,C（64）H（50）N8O（14）Dy2,Mr = 1480.12,Dc = 1.708 g/cm3,μ = 2.653 mm-1 and F（000） = 734.The final R = 0.0366 and w R = 0.0736 for 5816 observed reflections with I 〉 2σ（I）.Compound 1 contains the mononuclear [Dy（QLC）2（1,10-phen）] subunit formed from one 1,10-phen and two QLC-ligands chelating Dy（III） ion.Two mononuclear [Dy（QLC）2（1,10-phen）] subunits are bridged by a pair of μ2-OH groups to give a centrosymmetric dinuclear [Dy2（μ2-OH）2（QLC）4（1,10-phen）2] with each Dy（III） ion being eight-coordinated.Detailed susceptibility measurements revealed that compound 1 does not show slow magnetic relaxation under zero direct-current field but exhibits field-induced slow magnetic relaxation under 2 kOe applied field.

Crystal Structure and Magnetic Properties of a Two-dimensional Compound{(Me2NH2)4[Co(SIP)2]·2(DMF)·3(H2O)}n

-

The Experiments Detecting of Real Magnetic Charges in Structures of Atoms and Substance

Magnetic neutron scattering in Y-type hexagonal ferrite crystals, studied by the author in 1968-1971 and presented in the article showed that the entire density of the so-called magnetic moments of Fe3+ ions can significantly shift from the position of their nuclei. As result of these shift the structure in form of the chain magnetic spiral is realized in ferrite lattice. The noted shifts of the “magnetic moments” served as the basis for the author’s assumption that these “moments” are “fig sheets” behind which the magnetic poles (magnetic charges) real existing in the shells of atoms are hidden. In this case, the scattering of neutrons is carried out by magnetic charges, and not theoretical surrogates in the form of magnetic moments. In addition to participating in atomic structures, magnetic charges populate potential conduction zones in conductors, where they are exist in compositions of magnetic dipoles. Under the influence of an external magnetic field, a polarization of magnetic dipoles is realized in the conductor, the field strengths of which are directed against the external magnetic field. It is these dipole magnetic fields that are responsible for such a well-known physical phenomenon as diamagnetism. Under the conditions of noted polarization of magnetic dipoles the author managed to perform mechanical separation of magnetic charges in pairs ±g and to charge experienced bodies (metal plates) by the magnetic charges of one sign. The fact of such a charging was detected through magnetostatic interaction between magnetic charges on the plates using highly sensitive torsion balances. This experiment is presented in detail in this article. The results of these experiments, as well as subsequent experimental and theoretical studies of the author, which, in general composition, were carried out from 1968 to the present, showed that magnetic charges are real structural components of the atoms and substance. So, for example, the atomic shells are not electronic but electromagnetic. The main reason that real magnetic charges were “buried alive” in the existing physical theories is the physics of their confinement in substance forces of which, in its rigidity, is many times greater than the electron confinement forces.

Structure and magnetic properties of Osn （n=11～22） clusters

The structure and magnetic properties of Osn （n=11～22） clusters are systematically studied by using density functional theory （DFT）. For each size, the average binding energy per atom, the second-order differences of total energies and the highest occupied molecular orbital （HOMO）–the lowest unoccupied molecular orbital （LUMO） gaps are calculated to analyze the stability of the cluster. The structures of Os14 and Os18 clusters are based on a close-packed hexagonal structure, and they have maximum stabilities, so n=14, 18 are the magic numbers. The 5d electrons play a dominant role in the chemical reaction of Osn clusters. The magnetic moments of Osn clusters are quenched around n=12, and when n=18～22 the value approximates to zero, due to the difference of electron transfer.

Synthesis,Crystal Structure,Physical Properties and Theoretical Studies of the New Ternary Sulfide with Closed Cavities:CsYb_7S_(11)

A novel ternary rare-earth sulfide, CsYb7S（11）, has been successfully synthesized by high-temperature solid-state reaction of an elemental mixture with modified Cs Cl flux. The single-crystal X-ray diffraction data reveal its orthorhombic symmetry in space group Cmca（no. 64） with a = 15.271（3）, b = 13.414（2）, c = 18.869（3） A°, V = 3865.2（2） A°^3, Z = 8, Mr = 1696.85, Dc = 5.832 g/cm^3, μ = 36.538 mm^-1, F（000） = 5768, the final R = 0.0225 and w R = 0.0517 for 2258 observed reflections with I 〉 2σ（I）, 2.67〈θ〈27.48o, w = 1/[σ^2（Fo^2） ＋（0.0443 P）2 ＋ 8.7453 P], where P =（Fo^2 ＋ 2Fc^2）/3, S = 1.036,（Δρ）max = 1.609 and（Δρ）min = –1.922. The remarkable structural feature is the dual tricapped Cs2@S18 cube closed cavities far apart within the three-dimensional [Yb7S（11）]-covalent bonding matrix. Magnetic susceptibility measurements show that the title compound exhibits temperature-dependent（50～300 K） para-magnetism and obey the Curie-Weiss law. Moreover, the optical gap of 2.03 Ev for CsYb7S11 was deduced from the UV/Vis reflectance spectroscopy and DFT study indicates an indirect band gap with an electronic transfer excitation of S-3p to Yb-5d orbital.

Synthesis, Crystal Structure, and Magnetic Properties of a New Dinuclear Iron Complex with Schiff Base Ligand

A new dinuclear iron（Ill） complex has been synthesized and structurally charac- terized by X-ray crystallography： [Fem2（L）（C6HsCOO）（SO4）（CH3OH）2]·CH3CN＇CH3OH （1, H3L = N,N＇-bis（salicylidene）q,3-diamino-2-propanol）. Complex 1 belongs to orthorhombic space group Pna21 with a= 11.4400（8）, b = 22.9705（2）, c = 12.5712（9）A, V= 3303.5（4）A3, Z= 4, F（000） = 1576, Dc= 1.531 g·cm-3, Mr= 761.36,μ = 1.007 mm-1, S = 1.014, the final R= 0.0505 and wR= 0.1018. The crystal packing is stabilized by intermolecular O-H…O hydrogen bonds, forming an extended one-dimensional chain structure. The temperature dependence of magnetic susceptibility measurement shows that antiferromagnetic interaction is propagated between the metal centers. Fit as dinuclear arrangement gave parameters ofJ= 19.7 cm-1, g = 1.89 and R2 = 0.9999.

Tunable Electronic and Magnetic Properties from Structure Phase Transition of Layered Vanadium Diselenide

The atomic geometry, structure stability, electronic and magnetic properties of VSe2 were systematically investigated based on the density functional theory（DFT）. Varying from 3D to 2D four VSe2 structures, bulk 2H-VSe2 and 1T-VSe2, monolayer H-VSe2 and T-VSe2 are all demonstrated as thermodynamically stable by lattice dynamic calculations. More interestingly, the phase transition temperature is dramatically different due to the lattice size. Finally, owing to different crystal structures, H-VSe2 is semimetallic whereas T-VSe2 is totally metallic and also they have different magnetic moments. Our main argument is that being exfoliated from bulk to monolayer, 2H-VSe2 transforms to T-VSe2, accompanied by both semimetallic-metallic transition and dramatic magnetic moment variation. Our calculations provide a novel structure phase transition and an efficient way to modulate the electronic structure and magnetic moment of layered VSe2, which suggests potential applications as high-performance functional nanomaterial.

Synthesis,Crystal Structures and Intermolecular Magnetic Coupling Mechanism of the Mononuclear Radical Complex[1-N-methyl-1,10-phenanthrolium][Ni(dmit)_2]

The mononuclear radical anionic complex [1-N-methyl-1,10-phenanthrolium][Ni（dmit）2]（dmit = 1,3-dithiole-2-thione-4,5-dithiolate） with a new countercation has been prepared and its crystal structure was determined by X-ray crystallography at 298 and 80 K. In the mononuclear radical anionic complex, the nickel ion assumes a slightly distorted square-planar geometry. There are two and three kinds of intermolecular interactions between adjacent mononuclear radical anionic complexes in the crystal at 298 and 80 K, respectively（i.e., Models A and B at 298 K; and Models C, D and E at 80 K）. The variable-temperature magnetic moments indicate a strong antiferromagnetic interaction between the adjacent mononuclear radical anionic complexes, and the theoretical calculations reveal that the stronger antiferromagnetic coupling strength at lower temperature should be contributed to the larger overlap integrals between the short contact atoms. This study is the first to reveal the mechanism of stronger magnetic coupling strength at lower temperature for a mononuclear radical anionic nickel complex with dmit as the ligand.

A Single-Crystal Neutron Diffraction Study on Magnetic Structure of the Quasi-One-Dimensional Antiferromagnet SrCo_2V_2O_8

The magnetic structure of the spin-chain antiferromagnet SrCo2 V208 is determined by single-crystal neutron diffraction experiment. The system undergoes a long-range magnetic order below the critical temperature TN=4.96 K. The moment of 2.16#B per Co at 1.6K in the screw chain running along the c axis Mternates in the c axis. The moments of neighboring screw chains are arranged antiferromagnetically along one in-plane axis and ferromagnetieally Monk the other in-plane axis. This magnetic configuration breaks the four-fold symmetry of the tetragonM crystal structure and leads to two equally populated magnetic twins with the antiferromagnetic vector in the a or b axis. The very similar magnetic state to the isostructural BaCo2 V~ 08 warrants SrCo2 V2 08 as another interesting half-integer spin-chain antiferromagnet for investigation on quantum antiferromagnetism.