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.

Synthesis, Crystal Structure and Magnetic Properties of a One-dimensional Loop-like Iron(Ⅱ) Complex:[Fe(Haip)_2(H_2O)_2]_n (Haip = 5-Ammoniumisophthalato)

An iron（Ⅱ） coordination polymer, [Fe（Haip）2（H2O）2]n （1, Haip = 5-ammoniumiso- phthalato）, has been hydro/solvothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectrum and magnetic measurement. Compound 1 crystalizes in monoclinic, space group P2/c with a = 6.9874（14）, b = 9.960（2）, c = 12.894（4） A, β = 117.47（2）°, Fe（C8H6NO4）2（H2O）2, Mr = 452.16, V= 796.2（3） A3, Z = 2, Dc = 1.886 g.cm-3, p = 1.017 mm-1, F（000） = 464.0, 2.71〈0〈28.42°, R = 0.0307, wR = 0.0840 and S = 1.005. Single-crystal X-ray diffraction analysis reveals that 1 features an infinite one-dimensional loop-like chain structure and Haip ligand in 1 is of zwitterionic form. Magnetic measurement results show the dominated ferromagnetic interactions among Fe11 atoms.

Structural and Magnetic Studies of Ga-doped Yttrium Iron Garnet

Ga-doped Yttrium Iron Garnet (Y_(3)Ga_(x)Fe_(5-x)O_(12),Ga:YIG) was prepared by solid state reaction method and sintering at 1 300 ℃.Rietveld analysis of X-ray diffraction patterns indicated that all samples crystallized in a single cubic structure (space group Ia-3d) with decreasing lattice constant as Ga concentration increased.SEM surface micrograph images of YIG samples showed highly compacted grains with small reduction in the grain size with increasing Ga concentration.Raman spectroscopy measurements confirmed the replacement of Fe^(3+) ions by Ga^(3+) ions in the garnet structure was revealed by the observed blue shifts in Raman spectra.The saturation magnetization decreased from 28.2 to 4.98 emu g^(-1) with increasing x from 0.0 to 1.0 due to the preferential substitution of Ga^(3+) ions for Fe^(3+) ions at tetrahedral sites.Room temperature Mössbauer spectra for the samples revealed a reduction of the hyperfine field values for octahedral and tetrahedral sites,and the development of additional components with increasing Ga concentration.Analysis of the magnetic data and Mössbauer spectra confirmed that spin canting in the substituted garnets plays an important role in explaining the observed reduction of the saturation magnetization as x increased.

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.

Structure and Magnetic Property of an Oxygenand Carboxamide-bridged One-dimensional Iron(Ⅲ) Complex [Fe_2(μ-O)(bpb)_2]_n

The structure of the title complex [Fe2（μ-O）（bpb）2]n （bpb 2=1,2-bis（pyridine-2carboxamido） benzenate） has been characterized by single-crystal X-ray diffraction analysis.The complex （C36 H24 Fe2N8O5,Mr=760.33） crystallizes in the monoclinic space group P2 1/c with a=8.4615（17）,b=33.704（7）,c=11.173（2）,β=91.12（3）o,V=3185.7（11）3,Z=4,D c=1.585 g/cm 3,μ（MoK）=0.970 mm-1,F（000）=1552,R int=0.0381,the final R=0.0454 and wR=0.1114.The magnetic susceptibilities of the complex have been examined in the temperature range of 2-300 K.The magnetic data were fitted to give the parameters of J d=-77.7（9） and J c=-11.5（6） cm-1.

STRUCTURE AND MAGNETIC PROPERTIES OF YFe_(12-x)Ti_x COMPOUNDS

The structure and magnetic properties of the YFe12-xTix compounds (x=0.85, 1.00, 1.10, 1.20 and 1.30) have been investigated. Both the thermomagnetic analysis and X-ray diffraction patterns show that all compounds studied are almost single phase and crystallize in the ThMn12-type structure. The lattice parameters a, c and unit cell volume V increase monotonously with the increase of Ti content. Curie temperature Tc is almost independent on the Ti content while the spontaneous magnetization M0, the anisotropy field Ba and the anisotropy constant K1 decrease monotonously with the increase of Ti content and the temperature increases from 1.5 K to 293 K.

Synthesis of coral-like structures of Pr-Yb co-doped YIG: Structural,optical, magnetic and antimicrobial properties

Coral-like structures of the Y_(3-x)Pr_(x)Fe_(5-y)Yb_(y)O_(12),(0.00 ≤ x ≤ 0.04, 0.00 ≤ y ≤ 0.02) compound were synthesized using the sol-gel method. Structural investigation certified the YIG cubic crystal structure formation, without any secondary phase. It is shown that, the relatively large ionic radius of the dopant cations results in an expansion of the lattice parameter, variations in the Iona-O-Iondangle, Iona-O,Iond-O and Ionc-O bond distances and decrease in the average crystallite size. Fourier transform infrared(FTIR) and Raman measurements are essential to testify the single-phase formation of YIG crystal structure and are observed changes in the stretching and vibrational modes, respectively. The morphological study, energy dispersive spectroscopy(EDS) spectra and textural properties show corallike structures, peaks associated with Pr^(3+) and Yb^(3+) atoms and the effect of dopants on surface area,diameter, and pore volume, respectively. The optical analysis from diffuse reflectance spectra witnessed an increase in the optical gap band, a decrease in Urbach energy and blue shift in the charge transfer,correlated with the expansion of the unit cell due to the dopant's insertion in the YIG structure. A typical ferrimagnetic behavior is exhibited by the Y_(3-x)Pr_(x)Fe_(5-y)Yb_(y)O_(12)compound. The saturation magnetization(M_(s)), cubic anisotropy constant(K_(1)) and coercive field(H_(c)) increase with the Pr^(3+)cations content, as consequence of their magnetic nature and distribution around of Fe^(3+)ions due to the coexistence with the Yb^(3+). Finally, for the first time, antibacterial tests by mean of the direct contact method were performed for YIG co-doped with Pr^(3+)and Yb^(3+)and it is shown that, relatively high dosages of Pr^(3+) cations favored the activity against S. aureus, therefore, a new biological property for YIG doped with rare earths is presented.

Effect of La^(3+)substitution on structural,microstructure,magnetic properties,and microwave absorbing ability of yttrium iron garnet

Synthesis and characterization of lanthanum-doped yttrium iro n garnet(YIG)in the compositional se ries of Y_(3-x)La_(x)Fe_(5)O_(12)(x=0.0,0.1,0.3,and 0.5)were carried out.All compositions were made by using solid state reaction method with ball-milling technique.The phase formation,surface morphology,magnetic properties,and microwave absorbing ability of all compositions were characterized by using an X-ray diffractometer,a scanning electron microscope,a vibrating sample magnetometer,and a Vector network analyzer.The results reveal that all compositions are crystallized into Y_(3)Fe_(5)O_(12)phase(space group la-3d(230).It was observed that the lattice constant is increased from 1.2373 to 1.2421 nm with the increase of lanthanum substitution level from x=0.0-0.5.The crystallite size of Y_(3-x)La_(x)Fe_(5)O_(12)series calculated by Scherrer method is found to decrease from 78 nm in x=0.0-63 nm in x=0.5.The particle size distribution from the surface morphology image analysis is shifted to lower-range number with the increase of lanthanum substitution level from x=0.0 to 0.5.The substitution process also affects the lattice distortion in La-doped samples and changes the bond angles and bond lengths of the YIG structure.As the results,a linear correlation between the Fe'-O-Fe bond angle with magnetic properties parameters of saturation magnetization(M_(s))and remanence magnetization(M_(r))was studied.Due to the lanthanum substitution process,all La^(3+)-doped samples possess higher M_(s)and M_(r)values compared to the original composition.The results of Vector network analyzer show that the improvement of the M_(s)and M_(r)plays an important role in enhancing the microwave absorbing ability of the materials.The minimum RL changes from-8.22 dB(~85.22%microwave absorption)in x=0.0 to-14.21 dB(~96.25%microwave absorption)in x=0.5.The enhancement is mainly ascribed to the natural magnetic resonance loss and dipoIe-polarization loss due to the substitution process.The decreasing particle size also enhances the microwave absorbing ability of the La-doped samples via multiple-reflections mechanism.

Domain Structure of Iron Thin Films Prepared by Sputtering

Microstructure and magnetic domain structure of thin iron film prepared by sputtering were studied by magnetic force microscopy (MFM). Owing to the high lateral resolution of MFM magnetic structure of a single domain is able to be studied. Two series of iron thin films were grown on microcrystalline glass substrate by DC magnetron sputtering. They were prepared at different Ar pressure and annealing time. The results by magnetic force microscopy show both surface topography of the films and their local magnetic domain structure. It is suggested that the pin effect by single domain wall influence magnetic properties of the iron thin films.

Structure,magnetization, and magnetostriction of Sm-R-Fe (R=Pr,Nd) thin films

The structure, magnetization, and magnetostriction of Sm0.9Pr0.1Fex and Sm1-xNdxFel.9 thin films have been investigated using X-ray diffraction, vibrating sample magnetometer, and optical cantilever method. It is found that the structure of Sm0.9Pr0.1Fex thin films consists of an Sm-Pr-Fe amorphous phase when x≤2.69 and that of Sm1-xNdxFel.9 thin films consists of an Sm-Nd-Fe amorphous phase. The in-plane magnetization of Sm0.91Pr0.1Fex thin films increases with increase in the Fe content, and low values of the in-plane coercivity occur in the range of 1.62≤ x≤ 2.28. The magnetostriction value of Sm0.91Pr0.1Fex thin films increases with increasing the Fe content when x ≤ 1.94 and decreases when x 〉 1.94. The in-plane magnetostriction of Sm1-xNdxFe1.9 thin films under low magnetic fields has been improved by the substitution of Nd for Sm when x = 0.2.

核壳式球形铁基磁性磨料的制备及其抛光性能

[目的]混合式和镶嵌式磁性磨料的尺寸效应,以及磨粒出刃高度不一致所引起的抛光硬冲击问题亟待解决。[方法]将不规则铝粉与球形羰基铁粉均匀混合,通过加热扩散在接触界面生成金属间化合物并均匀分布在球形羰基铁粉表面,从而形成铁/铝核壳式球形磁性磨料,随后用它对氟化钙基片进行抛光。[结果]通过单因素试验优选出制备该核壳式铁基磁性磨料的最佳工艺参数为:反应时间4 h,反应温度770℃,Al含量质量分数12%。X射线衍射(XRD)、扫描电镜(SEM)观察、能谱(EDS)分析和磁化强度测试表明所得磁性磨料以羰基铁粉为内核,Fe Al、Fe_(3)Al、Fe_(0.4)Al_(0.6)等金属间化合物为壳,粒度符合正态分布,磨料相外壳分布均匀且出刃高度较为一致。氟化钙晶体经铁/铝核壳式磁性磨料抛光后表面变得光滑、平坦,粗糙度均方根值由初始的1.102μm下降到33 nm。[结论]所制备的核壳式球形铁基磁性磨料可用于软脆材料的磁力抛光。

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.

非晶合金-取向硅钢组合铁心结构设计及其磁-振动特性分析

非晶合金和取向硅钢是制作配电变压器铁心常用的两种软磁材料,各有优劣。采用非晶合金-取向硅钢组合铁心结构可以综合两者的优势。该文以非晶合金和取向硅钢铁心并排的组合结构为基础,选取组合铁心的取向硅钢占比和尺寸参数为自由变量,提出一种基于自由参数扫描法的组合铁心结构设计方法。首先,根据非晶合金-取向硅钢组合铁心结构特点,建立组合铁心的等效双非线性磁路模型;其次,采用磁路法迭代求解组合铁心的磁通密度分布,并制定组合铁心的结构设计流程;最后,根据结构设计结果制作了组合铁心的实验模型,采用实验和有限元仿真结合的方法分析了其磁-振动特性,验证了所提设计方法的准确性,并与传统纯非晶合金和纯取向硅钢铁心进行对比分析,阐述了组合铁心的优势。

高铁含量2∶17型钐钴永磁材料研究进展

新能源汽车和轨道交通等领域的快速发展对永磁材料的耐温能力和最大磁能积提出了更高要求。基于2∶17型钐钴(SmCo)磁体的高居里温度优势,适当增加铁对钴的替代量,是开发耐高温磁能积磁体的重要途径。然而,当铁的质量分数超过20%时,磁体中结构缺陷大幅增加,退磁曲线方形度和矫顽力急剧恶化,制约了最大磁能积的提升。基于高铁含量2∶17型SmCo永磁材料的研究现状及问题,本文从晶内和晶界两个方面概述了磁体中常见的结构缺陷,并总结了结构优化与磁性能提升的新进展,最后对高铁含量SmCo永磁材料的研究趋势进行了展望。

机械合金化制备铁基纳米晶合金的粉末粒度、结构演变和磁学性能

采用单质粉末混合物球磨1~24h制备Fe_(79)Mo_(10)B_(10)Cu_(1)合金粉末,考察合金粉末的粒度、结构和磁学性能。结果表明,延长球磨时间能够细化颗粒粒径(约8μm)和晶粒尺寸(约5 nm),并均匀化粒度分布和合金元素分布。Mo元素置换固溶于α-Fe,降低了合金粉末的饱和磁化强度,且在球磨15h后生成了纳米晶α-(Fe,Mo)单相固溶体,其晶格常数随Mo含量的增加而增大。在合金化前期(˂5h),由于残余应力和磁致伸缩系数的增大,磁弹各向异性成为矫顽力的主导因素,导致矫顽力随晶粒尺寸的减小而反常增大。球磨24h后合金的矫顽力为约2200A/m,微观压应变(约0.52%)和细小B夹杂物(˂1μm)是合金矫顽力较高的主要因素。

Structural, magnetic and electronic properties of the iron-chalcogenide AxFe2-ySe2 （A=K, Cs, Rb, and TI, etc.） superconductors

The latest discovery of a new iron-chalcogenide superconductor AXFe2-ySe2 （A =K, Cs, Rb, and Tl, etc.） has attracted much attention due to a number of its unique characteristics, such as the possible insulating state of the parent compound, the existence of Fe-vacancy and its ordering, a new form of magnetic structure and its interplay with superconductivity, and the peculiar electronic structures that are distinct from other Fe-based superconductors. In this paper, we present a brief review on the structural, magnetic and electronic properties of this new superconductor, with an emphasis on the electronic structure and superconducting gap. Issues and future perspectives are discussed at the end of the paper.

Influence of rare earth ion substitutions on the structural,optical,transport,dielectric,and magnetic properties of superparamagnetic iron oxide nanoparticles

Superparamgnetic Fe_3O_4 and RE:Fe_3O_4(RE=Dy,Nd,La)nanoparticles with an average crystallite size in the range of 15–24 nm,were synthesized by co-precipitation method.The samples were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),vibrating sample magnetometer(VSM),UV–Vis spectroscopy,LCR bridge,and two-probe technique.X-ray diffraction patterns of all the investigated samples reveal the typical phase of magnetite structure,with a small contribution of orthoferrite(NdFeO_3)as a secondary phase in Nd:Fe_3O_4 sample.The saturation magnetization(M_s)of the samples has values in the range from 41.8 to 52.3 emu/g,and decreases with RE ion doping depending on the ionic radius.Negligible values of the coercivity H_c and remanenceM_r,indicate the superparamagnetic nature of the investigated samples.The calculated values of indirect optical band gap of Fe_3O_4 and RE:Fe_3O_4 nanoparticles are in the range of0.9–1.25 eV.The dielectric constant of the samples decreases,while their activation energy increases with the increasing of ionic radii of dopants.

A 2D Cobalt(Ⅱ) Coordination Polymer [Co(iqnc)_2]_n: Synthesis, Crystal Structure and Characterization

A new cobalt（Ⅱ） coordination polymer with the formula of [Co（iqnc）2]n（1, iqnc = l-isoquinolinecarboxylate） has been synthesized through hydrothermal synthesis and structurally characterized by single-crystal X-ray diffraction method. The title coordination polymer represents a two-dimensional layer structure featuring adjacent one-dimensional [Co（iqnc）2]n chains connected with each other by uncoordinated oxygen atoms of carboxylate. Crystal data： monoclinic, space group P21/c, a = 15.4302（2）, b = 5.6743（7）, c = 9.2307（1） A, β = 98.459（2）o, V = 799.41（2） A3, Z = 2, S = 1.019, the final R = 0.0346, w R = 0.0876（I 2σ（I）） and R = 0.0477 and wR = 0.1159 for all reflections. In addition, elemental analysis, IR, and magnetism properties are presented.

Preparation of Carbon Encapsulated Iron Nanoparticles with Very Thin Shells by DC Arc Discharge

Carbon encapsulated iron nanoparticles （CEINPs） with very thin shells and good core-shell structures were prepared by DC arc discharge at argon intake temperature （AIT） of 800 ℃. The results of high resolution transmission electron microscope （HRTEM）, energy dispersive X-ray （EDX） spectroscope, X-ray diffraction （XRD）, and X-ray photoelectron spectroscope （XPS） characterizations on the product B show that the thickness of the carbon shells of CEINPs in the product B is in the range of ca. 0.5-5.3 nm, i. e., which can be as thin as only two layers of graphite. The average diameter of the CEINPs is about 24. 7 nm. The total content of Fe element in the product B is 77.0 wt%. The saturation magnetization （Ms） and coercivity （Hc） of the product B are 107.4 emu/g and 143 Oe. resnectivelv. The formation of the CEINPs in the oroduct B is discussed briefly.

桐城市高谷岭铁矿成矿地质特征及找矿方向

高谷岭铁矿是位于桐城市罗岭镇的一处小型隐伏铁矿床,以钻探、地质测量、地形测量、样品分析测试等手段揭露矿区地层、构造、岩浆岩分布、矿体规模及赋存状态等地质特征,在此基础上结合物探异常特征进一步研究矿区岩浆岩的类型、成矿物质来源以及物探异常与矿体的关联,以查明矿床成因类型及控矿因素。结果表明:本矿区矿体赋存于杂岩体中,受构造控制明显,主要为正长岩、二长岩、闪长岩等。矿石自然类型主要为阳起石磁铁矿、磷灰石阳起石磁铁矿、黑云母阳起石磁铁矿类型、浸染状正长岩磁铁矿;其次为石膏阳起石磁铁矿、阳起石赤(镜)铁矿等;工业类型为需选贫磁铁矿石。同时区内磁异常多为磁铁矿(化)体引起,二者关联性较好,下一步找矿可围绕区内尚未有工程验证的磁异常开展工作。