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.

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.

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.

Physical properties and magnetic structure of a layered antiferromagnet PrPd0.82Bi2

We report the physical properties, crystalline and magnetic structures of singe crystals of a new layered antiferromagnetic(AFM) material PrPd0.82Bi2. The measurements of magnetic properties and heat capacity indicate an AFM phase transition at TN^7K. A large Sommerfeld coefficient of 329.23 m J·mol-1·K-2 is estimated based on the heat capacity data, implying a possible heavy-fermion behavior. The magnetic structure of this compound is investigated by a combined study of neutron powder and single-crystal diffraction. It is found that an A-type AFM structure with magnetic propagation wavevector k =(0 0 0) is formed below TN. The Pr3+ magnetic moment is aligned along the crystallographic c-axis with an ordered moment of 1.694(3) μBat 4K, which is smaller than the effective moment of the free Pr3+ ion of 3.58 μB.PrPd0.82Bi2 can be grown as large as 1 mm×1 cm in area with a layered shape, and is very easy to be cleaved, providing a unique opportunity to study the interplay between magnetism, possible heavy fermions, and superconductivity.

Magnetic Structure of Continental Crust: Implications for Crustal Structure and Evolution

Magnetic structure of the continental crust is one of the important geophysical aspects of continental lithosphere. This paper reviews the achievements in the research into the magnetic structure and its significance for crustal tectonics, composition, metamorphic facies, crust mantle interaction and magnetization of deep crust. Further studies are suggested according to the basic principles of rock and mineral magnetism in terms of petrology, geochemistry and structural geology. Emphasis is placed on new geological ideas and synthetic studies of the relationship between deep geological processes and interpretation of gravity, magnetic, electrical and seismic data. The relationships between magnetic, density, electricity, velocity, geothermal structures and deep geodynamic processes are taken as a system for the research into the deep geology.

A single-crystal neutron diffraction study on magnetic structure of CsCo_2Se_2

The magnetic structure of CsCo_2 Se_2 was investigated using single-crystal neutron diffraction technique. An antiferromagnetic transition with the propagation vector（0,0,1） was observed at TN= 78 K. The Co magnetic moment 0.772（6） μB at 10 K pointing in the basal plane couples ferromagnetically in the plane, which stacks antiferromagnetically along the c direction. Tuning and suppressing the interplane antiferromagnetic interaction may be crucial to induce a superconducting state in the material.

Survey on the Magnetic Structure of the Neutral Sheets in Earth's Magnetotail

Based on the multipoint magnetic observations of Cluster from 2001 to 2004,the magnetic field structure in magnetotail Neutral Sheet(NS) is statistically surveyed.The results are as follows.In NS,a cubic function is selected to reveal the relation between y(GSM) and positional parameter z.The relation between y and magnetic field values indicates that the magnetic field is weak at midnight region and strengthens gradually at the duskside and dawnside.The relation between y and curvature radius is expressed by a quadratic function.And R_c of flattened CS is less than that of the normal CS.B_y determines the orientation of MFLs' configuration.The polar angle of the curvature vector is affected by the NS configuration.In addition,the correlation between the polar angle of the curvature vector and z is higher.The polar angle of the normal of the osculating plane is uncertain in the center area.The relation between the azimuthal angles of the curvature vector(the normal of the osculating plane) and y is negatively correlated.An empirical model applied to yz plane of the three-dimensional structure of the magnetic field lines in the NS are developed,and it is represented as a function of the positional parameter y.Finally,the current density is also statistically surveyed.

Neutron Diffraction Study on the Magnetic Structure of 153EuMnO3-δ: One Way to Assess the Magnetic Structure of EuMnO3-δ

Owing to the strong neutron absorption of 151Eu,151Eu free 153EuMnO3-δhas been synthesized to collect the neutron diffraction data for analyzing the magnetic structure of EuMnO3-δ.The obtained neutron diffraction data of 153EuMnO3-δindicates that the magnetic diffraction peaks corresponding to cAAFM(canted A-type antiferromagnetic)phase can be observed,but the magnetic diffraction peaks corresponding to expected ICAFM(incommensurate antiferromagnetic)phase may be too weak to be observed.

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.

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.

Magnetic structure of Pr_6Fe_(13)Ge studied by Mossbauer effect and neutron diffraction

Magnetic structure of Pr6Fe13Ge at room temperature has been investigated by magnetic measurement, Mossbauer effect and neutron diffraction. Magnetic atoms are closely packed up and down the mirror planes at z = 0 and 1/2 and separated by the non-magnetic atoms located on the planes at z= 1/4 and 3/4, which constructs an M/NM/M sandwich structure (M: magnetic, NM: non-magnetic). The intralayer magnetic moments couple ferromagnetically and are out of ab plane at a small angle so as to form a component along c-axis. The interlayer coupling is antiferromagnetic for the ab component while ferromagnetic for the c component.

Electronic and magnetic structures of ternary iron telluride KF2T2

We examine the electronic and magnetic structures of iron telluride KFe2Te2 using first-principle calculations. We demonstrate that the ground state of this compound is in bicollinear antiferromag- netic order with Fe local moments （- 2.6 μB） that are ferromagnetically aligned along a diagonal direction and antiferromagnetically aligned along the other diagonal in the Fe-Fe square lattice, sim- ilar to the alignment discovered in the parent compound of superconductor α-FeTe. This bicollinear antiferromagnetic order results from the interplay among the nearest, next-nearest, and next-next- nearest neighbor exchange interactions, which are mediated by Te 5p orbitals. This finding may aid our understanding of the interplay between magnetism and superconductivity in the family of iron-based materials.

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.

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.

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

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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, 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.