Crystal and magnetic structure of UCuSn

A polycrystalline sample of antiferromagnet UCuSn has been studied by neutron diffraction. The data obtained at 90 K (paramagnetic state) indicate that the crystal structure is hexagonal with an ordered distribution of Cu and Sn atoms in the unit cell (P6₃mc). In the antiferromagnetic state, the uranium moments with a value of 1.9(1)μ_B lie in the bc plane and form an angle of 25° with the b-axis. The magnetic space group UCuSn is P2′₁m′c.     

Crystal and electronic structure and magnetic properties of CeRhPb

The new intermetallic cerium compound CeRhPb was synthesized by arc melting and studied by means of X-ray diffraction and magnetic measurements. The crystal structure determined from the single-crystal X-ray data is of the ZrNiAl type (space group P6¯2m). The compound was found to be a Pauli paramagnet with 4f⁰ ground state of the Ce atoms. The ab-initio band structure calculations performed without and with spin polarization confirmed the nonmagnetic character of the plumbide studied.     

Crystal structure and magnetic ordering of RNi Si compounds

The element distributions and the magnetic ordering behaviour of compounds RNi₁₀Si₂ (R = Tb, Dy, Ho, Er, Tm) have been studied by neutron powder diffraction down to temperatures of 1.6 K. The compounds crystallize in an ordered variant of the ThMn₁₂ structure type in the tetragonal space group P4/nmm. An ordered 1:1 distribution of Ni and Si on sites 4d and 4e, respectively, corresponds to a modulation vector [0, 0, 1] with respect to the space group I4/mmm of the ThMn₁₂ structure. TbNi₁₀Si₂ orders antiferromagnetically below T _N = 4.5 K with a magnetic propagation vector of [0, 0, 1/2]. The magnetic Tb moments, 8.97(2) /Tb atom at 1.6 K, are aligned along the c-axis. The Ni sites in TbNi₁₀Si₂ do not carry any ordered magnetic moments. The compounds with R = Dy, Ho, Er, and Tm are paramagnetic down to 1.6 K and 3.0 K, respectively. Received 10 July 2002 / Received in final form 12 September 2002 Published online 29 October 2002     

Crystal and magnetic structure of KFeO2

The crystal and magnetic structures of KFeO₂ have been determined by neutron and X-ray powder-diffraction and Mössbauer-effect techniques. The crystal structure at 4.2 K and 300 K is orthorhombic and the magnetic space group is Pbca'. The Fe³⁺-ions in this structure are tetrahedrally coordinated by oxygen ions, and each Fe³⁺-ion has a magnetic moment which is antiferromagnetically coupled to the moments of four Fe³⁺-neighbours. The direction of the moments is parallel to the a-axis. A crystal phase transition has been observed near the Néel temperature?960 K.     

Crystal structure and the magnetic properties of CeTiGe3

The crystal structure of the RTiGe₃ compounds (R=La, Ce and Pr) has been studied by X-ray powder diffraction methods; Rietveld refinement has been carried out on the La homologue. These compounds crystallise in the BaNiO₃ prototype structure, hP10-P6₃/mmc, also called the hexagonal perovskite (a=6.300(1), c=5.915(1) Å for LaTiGe₃). This seems to be the first example in which an intermetallic phase adopts such a structure type which can be considered as derived from the Ni₃Sn type (anti) by a distortion of the lattice and the occupation of the quasi-octahedral 2a site at the origin of the cell (0, 0, 0) by Ti. The composition, also confirmed by microprobe analyses, was found to be strictly 1:1:3 indicating that these are line compounds, forming very likely by a peritectoid reaction. The existence of homologous compounds has been established for the lighter rare earths La, Ce and Pr. Heat capacity and magnetisation data show that CeTiGe₃ orders ferromagnetically with a Curie temperature of nearly 14 K. On the other hand a−ln T variation of the magnetic part of the resistivity below 300 K is consistent with that expected for single impurity Kondo behaviour. CeTiGe₃ is thus an uncommon example of a ferromagnetic dense Kondo lattice.     

Crystal structure,thermal expansion and magnetic properties of Nd2Cu0.8Ge3 compound

A new ternary intermetallic compound, Nd₂Cu_0.8Ge₃, was synthesized and its crystal structure was determined by Rietveld refinement of X-ray powder diffraction data. The Nd₂Cu_0.8Ge₃ compound crystallizes in space group I4₁/amd (No. 141), with a tetragonal a-ThSi₂ structure type, and a=0.41783(2) nm, c=1.43689(9) nm, Z=2 and D_calc=7.466 g/cm³. Using the high temperature powder X-ray diffraction (HTXRD) technique, the lattice thermal expansion behavior of the compound was investigated in the temperature range of 298–648 K, and the result shows that its unit-cell parameters increased anisotropically when temperature increased. The magnetic susceptibility measured in the temperature range of 5–300 K indicated antiferromagnetic order of Nd₂Cu_0.8Ge₃ at low temperatures, and the magnetic susceptibility can be well described over the range of 50–300 K using Curie–Weiss law. The calculated effective magnetic moment (μ_eff) is 3.53 μ_B and dominated by the contribution of the Nd³⁺ ions.     

Crystal structure and magnetic properties of lepidocrocite upon thermal transformation to hematite

Synthesized lepidocrocite (-FeOOH) has a unit cell of the rhombic system (a = 3.86 Å, b = 12.49, and c = 3.36). In the 230–250°C region the structure of lepidocrocite is reconstructed to cubic (a = 8.331 ± 0.003 A) maghemite (-Fe₂O₃), which at 375°C is transformed completely to hematite (-Fe₂O₃) with a hexagonal structure which becomes more perfect with further heating (a = 5.0330 ± 0.002 Å, c = 13.748 ± 0.002 Å). Lepidocrocite occurs in a paramagnetic state. The intermediate substance of its thermal transformation, maghemite, as a consequence of high dispersion, is characterized by superparamagnetic properties and the end product, hematite, owing to the presence of Dzialoshinski's moment, has weak ferromagnetism.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 84–90, May, 1972.     

Crystal and magnetic structure of Ho2NiGe6

The crystal and magnetic structure of Ho₂NiGe₆ was studied by powder neutron diffraction. The paramagnetic neutron diffraction data confirmed the Ce₂CuGe₆-type crystal structure reported earlier for this compound. Below the Néel temperature equal to 11 K the Ho magnetic moments form a uniaxial antiferromagnetic ordering. The Ho magnetic moments equal to 8.16(7)μ_B at 1.5 K are parallel to the b-axis. The data are compared with those published for HoNi_0.46(6)Ge₂.     

Crystal and magnetic structure of CeVO<Subscript>3</Subscript>

The crystal structure and the magnetic ordering pattern of the electrically insulating perovskite CeVO₃ was investigated by high-resolution powder X-ray diffraction and single-crystal neutron diffraction. A structural phase transition from an orthorhombic to a monoclinic structure (with space groups Pbnm and P2₁/b, respectively) was observed upon cooling below T _s = 136 K. This transition is associated with a strong distortion of the VO₆-octahedra and can be attributed to orbital ordering. A magnetic ordering transition driven by exchange interactions between vanadium moments is observed at T _N = 124 K, and antiferromagnetic interactions between magnetic moments on vanadium and cerium ions induce a progressive magnetic polarization of the cerium sublattice at lower temperatures. The full magnetic structure is described by a superposition of the modes (C _x , F _y , −) and (F _x , C _y , −). The unit cell volume and the tilt angles of the VO₆-octahedra in the CeVO₃-crystal structure are anomalous compared to those of other members of the series RVO₃ (R = lanthanide atom), and the ordered magnetic moments on both vanadium and cerium sublattices at low temperatures are considerably smaller than the free-ion values of V³⁺ and Ce³⁺. Possible origins of this behavior are discussed.     

Crystal structure and magnetic properties of disordered alloy ErGa_(3-x)Mn_x

ErGa_(3-x)Mn_x disordered alloy is successfully prepared by the vacuum arc melting technology, and the crystal structure and magnetic properties are investigated by using the x-ray diffraction and magnetic measurements. The Rietveld structural analysis indicates that the ErGa_(3-x)Mn_x crystallizes into a cubic structure with space group of Pm3m in Mn doping range of x = 0–0.1. However, the disordered alloy with structural formula of Er_(0.8)Ga_2~Ⅰ(Ga~Ⅱ, Mn)0.4 as the second phase is separated from cubic phase for the samples with x = 0.2 and 0.3, which is induced by substituting the(Ga~Ⅱ, Mn)–(Ga~Ⅱ, Mn) pair at 2e crystal position for the rare earth Er at 1 a site. The lattice parameters tend to increase with Mn content increasing due to the size effect at Ga(1.30°A) site by substituting Mn(1.40°A) for Ga. The paramagnetic characteristic is observed by doping Mn into ErGa_3 at room temperature. With Mn content increasing from x = 0 to 0.1, the magnetic susceptibility χtends to increase. This phenomenon can be due to the increase of effective potential induced by doping Mn into ErGa_3.However, the magnetic susceptibility χ continues to decrease with the increase of Mn content in a range of x 0.2, which is due to the phase separation from the cubic Er(Ga, Mn)_3 to the hexagonal Er_(0.8)Ga_2(Ga, Mn)_(0.4).     

Crystal and magnetic structure of the CoMn1−xTixSi system

The magnetic and crystallographic nature of the compounds CoMn_1?xTi_xSi (0?x?0.5) is studied by X-ray, neutron diffraction and magnetometric measurements. It is shown that the solid solutions arise for 0?x?0.5, with the crystal structure of the NiTiSi type. All compounds are antiferromagnets. The magnetic moment localized on Mn and Co atoms forms a double spiral in both sites. The dilution of the Mn sublattice by Ti atoms change only slightly the magnetic properties - Néel temperature and parameters of magnetic structure.     

Crystal structure and magnetic properties of HoPt2Si2

The crystal structure of HoPt₂Si₂ was determined using powder neutron diffraction data. It is tetragonal, CaBe₂Ge₂ type (space group P4/_n mm). Neutron diffraction and magnetometric measurements indicate that HoPt₂Si₂ remains paramagnetic at the temperature of 2.0 K.     

Crystal growth, structure and electrical properties of thorium phosphorosulfide

Single crystals of thorium phosphorosulfide have been grown by the chemical vapour transport method. The X-ray diffraction examination showed that the unit cell of the crystals belongs to a tetragonal system of the PbFCl-type structure. The basal plane resistivity ρ(300 K)=64 μΩ cm and thermoelectric power S(300 K)=−7.7 μV/K, examined between 0.4 and 315 K, show metallic behaviour.     

Crystal structure and magnetic properties of TbFe0.4Ge2 compound

Neutron diffraction and magnetic measurements were performed on polycrystalline TbFe_0.4Ge₂ which crystallizes with the orthorhombic structure of the CeNiSi₂-type. Despite the presence of some clear anomalies in the low-temperature magnetic susceptibility, the neutron diffraction experiment did not reveal any long-range magnetic ordering of the Tb magnetic moments down to 1.57 K.     

Crystal structure and the magnetic state of Pr0.5Sr0.5Co0.5Fe0.5O3

The magnetic properties and crystal structure of the Pr_0.5Sr_0.5Co_0.5Fe_0.5O₃ compound are studied by neutron and x-ray diffractions using synchrotron radiation. These measurements show that this compound is a dielectric spin glass with a magnetic moment freezing temperature of about 70 K. As temperature decreases in the range 30–95 K, a structure phase transition of the first order occurs with an increase in the symmetry from orthorhombic (space group Imma) to tetragonal (space group I4/mcm). It is assumed that the transition is caused by a change in the 4f electron configuration of the Pr³⁺ ions.     

Synthesis, structure, and magnetic properties of anion-substituted manganese chalcogenides

The anion-substituted solid solutions of the MnSe_{1 t x} Te _x system have been synthesized. The crystal structure and magnetic properties of the synthesized solid solutions have been investigated. It has been shown that, in the concentration range 0 ?? x ?? 0.4, the solid solutions have a face-centered cubic structure. It has been revealed that an increase in the concentration of the substituting element in the MnSe_{1 ? x} Te _x system leads to an increase in the coefficient of thermal expansion of the sample. The investigation of the magnetic properties has been carried out at temperatures in the range 80 K < T < 1000 K in a magnetic field up to 8.6 kOe. It has been experimentally found that the type of antiferromagnetic order (the second type of ordering) remains unchanged over the entire concentration range up to x = 0.4 and that the paramagnetic Curie temperature and the Néel temperature decrease within the limits of 20%. Theoretical calculations have been performed using the Monte Carlo method, and the model of nanoclusters with an uncompensated antiferromagnetic moment has been proposed.     

Tm掺杂的激光晶体生长、结构和光谱性能研究

采用顶部籽晶生长法从K2Mo3O10-B2O3助熔剂中生长出15 mm×15 mm×25 mm优质TmxGd1-x Al3(BO3)4(x=1,0.06)晶体.利用X射线单晶衍射仪测定了TmAl3(BO3)4晶体的结构.对Tm3+GAB晶体进行定向切割,测量得到了σ和π方向的偏振的吸收和发射光谱,并根据Judd-Ofelt理论计算了Tm3+在GdAl3(BO3)4中的J-O参数、各个能级的振子强度、自发辐射几率、荧光分支比等参数.