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1.
A new mixed-valence iron phosphate Na 1.25Mg 1.10Fe 1.90(PO 4) 3 has been synthesized as single crystals by a flux technique and its structure has been refined from X-ray data to a residual R1 = 0.032. The compound crystallizes in the monoclinic space group C2/ c with the parameters: a = 11.7831(3) Å, b = 12.4740(3) Å, c = 6.3761(2) Å, β = 113.643(2)° and Z = 4. The structure belongs to the alluaudite structural type, and thus it obeys to the X(2)X(1)M(1)M(2) 2(PO 4) 3 general formula. The X(2) and X(1) sites are occupied by sodium while the M(1) and M(2) sites feature a statistical distribution of iron and magnesium. Additional information about the cation distribution has been extracted from a Mössbauer spectroscopy study which confirmed the mixed valency of the compound. A magnetic susceptibility study has also been undertaken and has shown the compound to be antiferromagnetic with a Neel temperature of about 35 K. 相似文献
2.
A new ternary compound Ce(Au,Sb) 2, with a homogeneity range has been observed from X-ray powder diffraction of as cast alloys, a = 4.743–4.712 Å, c = 3.567–3.768 Å. Its crystal structure was investigated by X-ray diffraction from Ce(Au 1−xSb x) 2 ( x = 0.266) single crystal: CAD-4 automatic diffractometer, Mo K radiation, a = 4.7256(6) Å, c = 3.6711(6) Å, P6/ mmm space group, V = 70.997(17) Å 3, Z = 1, ρ = 10.732 Mg/m 3, μ = 76.369 mm −1, R1 = 0.0415, wR2 = 0.0793 for 99 reflections with I > 2 σ( I0). The coordination polyhedron of X (X = 0.734Au + 0.266Sb) atom is a full-capped trigonal prism [XCe 6X 3X 2]. Ce atom is coordinated by 14 atoms: [CeX 12Ce 2]. The compound is isotypic with UHg 2 structure, a deformation derivative of AlB 2 structure type. It forms isostructural compounds with La and Pr. 相似文献
3.
The nature of the magnetic ordering of Tb 4Sb 3 compound (Th 3P 4-type, cubic; cI28, space group , No. 220, a = 0.91518(7) nm) has been investigated by using the techniques of magnetization and neutron diffraction. AC and DC magnetisation measurements indicate antiferromagnetic ordering at 108 K in zero magnetic field that is accompanied by a field-induced metamagnetic transition to a ferromagnetic state, in fields above 0.3 T. Neutron diffraction experiment in zero applied magnetic field shows that below TN = 112(4) K Tb 4Sb 3 exhibits an antiferromagnetic flat spiral-type ordering with propagation vector K 1 = [±1/8, ±1/8, ±1/8]. The magnetic moment of Tb atoms is found to be MTb = 6.7(3) μ B at 80 K. The magnetic moment of Tb atoms lie in the (1 1 1) plane of Tb 4Sb 3 unit cell (the cone axis arranges along [1 1 1] direction with cone angle β = 90°). Below TN2 50 K, Tb 4Sb 3 shows second antiferromagnetic transition with K 2 = [1/2, 1/2, 1/2] with possible re-orientation of Tb magnetic moments. 相似文献
4.
The Nd 11Pd 4In 9 compound was prepared by arc melting of pure metals under an argon atmosphere. Crystal structure was refined from X-ray single crystal diffractometer data (space group Cmmm, a = 14.843(3), b = 22.284(3), c = 3.7857(6) Å, Z = 2, RI = 0.0584, 653 F2 values). It has own structure type and together with Mn 2AlB 2, Cr 3AlB 4, Mo 2FeB 2 and Lu 5Ni 2In 4 structure types belongs to homological series based on AlB 2 and CsCl structure types with common formula R m+nM 2nX m. 相似文献
5.
Magnetic properties and magnetocaloric effects of Pr 6Co 1.67Si 3 compound have been investigated by magnetization measurements. The saturation moment at 5 K is found to be 10.7 μB. The compound undergoes two magnetic transitions below Curie temperature TC = 48 K and shows a reversible second-order magnetic transition around TC. A magnetic entropy change Δ S = 6.9 J/(kg K) is observed for a magnetic field change from 0 to 5 T. The full width at half maximum of the Δ S peak is found to be about 38 K. 相似文献
6.
A new compound CePt 2+xSb 2−y ( x = 0.125, y = 0.25) was synthesized by arc-melting of the elements. The chemical and structural characterizations were carried out at room temperature on as-cast samples using X-ray diffractometry, metallographic analysis and EDS-microanalysis. According to the results of X-ray single crystal diffraction this antimonide crystallizes in I4 cm space group (no. 108), Z = 32, ρ = 12.19 Mg/m 3, μ = 89.05 mm −1 ( a = 12.5386(3) Å, c = 21.4692(6) Å (crystal I) and a = 12.5455(2) Å, c = 21.4791(5) Å (crystal II)). The structure and composition were confirmed by powder X-ray diffraction ( a = 12.4901(2) Å, c = 21.3620(4) Å) and EDS-microanalysis respectively. Isotypic compounds were observed with La and Pr from X-ray powder diffraction of as-cast alloys at room temperature ( a = 12.6266(4) Å, c = 21.4589(6) Å for LaPt 2+xSb 2−y and a = 12.5184(5) Å, c = 21.4178(7) Å for PrPt 2+xSb 2−y). The CePt 2+xSb 2−y structure is derived from CaBe 2Ge 2 ( a = 2 a0 − 2 b0, b = 2 a0 + 2 b0, c = 2 c0) and comprises a new atomic arrangement with both vacancy on 4(b) pyramidal site and substitution of antimony atoms (X) by platinum (B) in the B–XX–B layers (referring to the subcell structure) forming two B––1/2B1/2XX–3/4B and two X–BB–X layers per cell. The structure of CePt 2+xSb 2−y is compared with those reported before for URh 1.6As 1.9 and CeNi 1.91As 1.94. 相似文献
7.
Two ternary alkali earth silver bismuthides, CaAgBi and BaAg 1.837Bi 2, have been synthesized by solid-state reactions of the corresponding metals in welded Nb tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. CaAgBi crystallizes in the hexagonal space group P6 3mc (No.186) with cell parameters of a = b = 4.8113(4) Å, c = 7.8273(9) Å, V = 156.92(3) Å 3, and Z = 2. BaAg 1.837Bi 2 belongs to tetragonal space group P4/ nmm (No.129) with cell parameters of a = b = 4.9202(2) Å, c = 11.628(1) Å, V = 281.50(3) Å 3, and Z = 2. The structure of CaAgBi is of the LiGaGe type, and features a three-dimensional four-connected (3D4C) anionic network with Ca 2+ encapsulated in the channels formed by [Ag 3Bi 3] six-membered rings. BaAg 1.837Bi 2 is isostructural with CaBe 2Ge 2, a variant of the tetragonal ThCr 2Si 2-type structure. Its structure exhibits a three-dimensional anionic network built of (0 0 1) and (0 0 2) puckered [Ag 2Bi 2] layers interconnected via additional Ag–Bi bonds along the c-axis. BaAg 1.837Bi 2 is metallic based on band structure calculations. 相似文献
8.
Two polymorphs (I and II) of Ba 3Sn 2P 4 have been found in the same preparative batch. Both compounds crystallize in the centrosymmetric monoclinic space group P2 1/ c (#14, a = 7.8669(2) Å, b = 19.2378(5) Å, c = 7.8472(2) Å, β = 112.77(1)°, V = 1095.06(5) Å 3, Z = 4, and R/ wR = 0.0303/0.0710 for I; a = 7.8771(3) Å, b = 19.4099(7) Å, c = 7.7040(3) Å, β = 112.44(1)°, V = 1088.67(7) Å 3, Z = 4, and R/ wR = 0.0224/0.0415 for II). Both structures consist of one-dimensional chains separated by Ba 2+ cations. The isolated chain consists of condensed ethane-like [Sn 2P 6] units. In polymorphs I and II, the condensation and connectivity of the [Sn 2P 6] units are quite different. While [Sn 2P 6] units form four- and six-membered rings in I, they form the five-membered rings in II. The electronic structure calculations indicate that semiconducting behavior is expected for both compounds. 相似文献
9.
The new compound Li 2VGeO 5 with a layered structure has been synthesized at 580 °C via the hydrothermal method. The compound crystallizes in the space group P4/ n of the tetragonal system with two formula units in a cell of dimensions a=6.5187(9) Å, c=4.5092(9) Å ( T=298 K), V=191.61(5) Å 3. The structure is composed of layers made of repeating [(VO 5)(GeO 4)] 1− units. Li + ions reside between the layers. The magnetic susceptibility data show an antiferromagnetic coupling below 5 K with C=0.47 emu K mol −1, and θ=−13 K with μ eff=1.89 μB for each Li 2VGeO 5 unit. 相似文献
10.
In our investigation of non-centrosymmetric rare earth sulfides in the La 3AgSnS 7/KBr, LaAlGeS 5/NaBr, HoAlGeS 5/KBr, ErAlGeS 5/NaBr, Er 3AgGeS 7/KBr and La 3NaSnS 7/NaBr systems, five compounds belonging to the R 6B 2C 2Q 14 family have been obtained. These compounds crystallize in the P6 3 space group, and the crystal data are as follows—La 3AgSnS 7: a = 10.3780(15) Å, c = 5.9900(12) Å, Z = 2; La 3Ge 0.25GeS 7: a = 10.2970(15) Å, c = 5.8120(12) Å, Z = 2; Ho 3Ge 0.272(10)GeS 7: a = 9.6480(14) Å, c = 5.7920(12) Å, Z = 2; Er 3Ge 0.330(10)GeS 7: a = 9.5930(14) Å, c = 5.8490(12) Å, Z = 2; La 3Sn 0.25SnS 7: a = 10.2770(15) Å, c = 6.0030(12) Å, Z = 2. Single-crystal analysis indicated that the crystal structures consist of three types of building block: LnS n, MS 4, and AgS 3 (for La 3AgSnS 7) or MS 6 units (for Ln 3M xMS 7, Ln = La, Ho, Er; M = Ge, Sn; 1/4 ≤ x ≤ 1/2), as any other compounds belonging to the R 6B 2C 2Q 14 family. Ln 3M xMS 7 (Ln = La, Ho, Er; M = Ge, Sn; 1/4 ≤ x ≤ 1/2) are deficient compounds with the B sites occupied partly by M(II), and/or M(IV). 相似文献
11.
Investigations were made by neutron diffraction on Zr 6CoAs 2-type (space group no. 189) Ho 6−xEr xMnBi 2 solid solutions. The ferromagnetic ordering temperature decreases from Ho 6MnBi 2 ( TC = 200(6) K) to Er 6MnBi 2 ( TC = 100(4) K), whereas temperatures of ferrimagnetic (or antiferrimagnetic) ordering ( TFerri and TAFerri) are found to have non-monotonic dependences on the content of Er: TFerri = 58(4) K for Ho 6MnBi 2, TFerri = 162(4) K for Ho 4.5Er 1.5MnBi 2, TFerri = 150(4) K for Ho 3Er 3MnBi 2, TAFerri = 78(4) K for Ho 1.5Er 4.5MnBi 2 and TAFerri = 52(4) K for Er 6MnBi 2. In these compounds, no local moment was detected on the manganese ion site, except for Ho1.5Er4.5MnBi2 and Er6MnBi2 compounds. The manganese magnetic moments (μMn) is 1.5μB and these are antiferromagnetically coupled with that of rare earth moments. 相似文献
12.
In our investigation of Co-rich alloys in the ternary U–Co–Sn system, we have identified three intermetallic compounds with composition UCo 2Sn, UCo 4Sn and UCo 5Sn, respectively. The existence and the crystal structure of the first compound, already known in the literature, have been confirmed, while the latter two compounds have been identified for the first time. The crystal structure of these compounds was determined by X-ray diffraction methods, performed both on powders (all samples) and single crystals (UCo 4Sn and UCo 5Sn). The crystal data are as follows (lattice constants from Guinier powder patterns): UCo 2Sn [UPd 2Sn-type, orthorhombic, oP16- Pnma, a = 9.402(3), b = 4.321(1), c = 6.615(2) Å], UCo 4Sn [MgCu 4Sn-type, cubic, , a = 6.992(2) Å] and UCo 5Sn [CeCu 4.38In 1.62-type, orthorhombic, oP56- Pnnm, a = 10.250(1), b = 16.012(2), c = 4.837(1) Å]. The physical properties of the compounds have been studied by electric transport (1.5–300 K), heat capacity (1.8–40 K) and magnetic measurements (1.8–300 K). The magnetisation data reveal weakly paramagnetic behaviour (with weak low temperature upturn due to parasitic impurity phases) in all the three alloys and absence of long-range magnetic ordering, despite the presence of uranium and a substantially high concentration of cobalt. The results for UCo 2Sn are in agreement with earlier reports in the literature. The magnitudes of the coefficients of the linear term in the heat capacity and the T2 term in the low temperature resistivity track the room temperature magnetisation. 相似文献
13.
Bulk metallic glasses (BMGs) Fe 61Co 6Zr 8−xHf xMo 7B 15Al 1Y 2 ( x = 0–8) have been produced by copper mold casting technique using industrial raw materials. The effect of substitution of Hf for Zr on the glass forming ability (GFA) and the magnetic property has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). It was found that the substitution of an appropriate amount of Hf for Zr can improve the GFA of the base alloy Fe 61Co 6Zr 8Mo 7B 15Al 1Y 2, as demonstrated by the increase in reduced glass transition temperature Trg (= Tg/ Tl) and GFA parameters of γ (= Tx/ Tg + Tl) and δ (= Tx/ Tl − Tg). The Fe 61Co 6Zr 5Hf 3Mo 7B 15Al 1Y 2 alloy exhibits the highest GFA with the largest Trg (0.612) and δ (1.633), and can cast a fully amorphous rod in 3 mm diameter. The substitution of Hf for Zr also enhances the magnetic properties, as verified by the increase in saturation magnetization ( Ms) in the alloy of Fe 61Co 6Zr 3Hf 5Mo 7B 15Al 1Y 2, whose Ms is approximately 1.5 times higher than that of the base alloy ( x = 0) at room temperature. Finally, the effect of the substitution of Hf for Zr on glass forming ability and magnetic properties is discussed. 相似文献
14.
The crystal structure of Y 3TaNi 6+xAl 26 (refined composition Y 4TaNi 6+[7]Al 20+[6]) was determined by single-crystal X-ray diffraction (λ(Mo K) −0.71073 A. μ −17.827 mm 1, F(000) = 700, T = 293 K, wR = 0.015 for [8] unique reflections). This new quaternary aluminide crystallizes with a cubic structure. Pearson code cP49-12.85, (221) Pm-3m-ji'gdba, a = 8.3600(1) Å. V = 584.28(2) Å, Z = 1, M1 = 1510.25, Dx = 4.292 mg mm 1. The structure of Y xTaNi 6+xAl 26 is filled-up substitution variant of the BaHg 11 structure type with one additional atom site, partly occupied (around 15%) by Ni atoms, located at the centre of a cube formed by Al atoms. Distinct atom coordinates were refined for Ni and Al atoms on a site for which mixed occupation (approximately 50% Ni/50% Al) was found. The Ta atoms centre regular Al atom cuboctahedra, and the Y atoms 20-vertex polyhedra, formed by Al and Ni atoms, similar to those observed in CeMn 4Al 8 and YbFe 2Al 10. 相似文献
15.
A neutron diffraction investigation has been carried out on the trigonal La 2O 3-type ( hP5, space group , No. 164; also CaAl 2Si 2-type) YbMn 2Sb 2 intermetallic. A two-step synthesis route has been tried in this work, and successfully utilised to prepare single phase samples of this compound. This study shows that YbMn 2Sb 2 presents antiferromagnetic ordering below 120 K. The magnetic structure of this intermetallic consists of antiferromagnetically coupled magnetic moments of the manganese atoms, in the Mn1 (1/3, 2/3, ZMn) and Mn2 (2/3, 1/3, 1 − ZMn) sites; the direction of magnetic moments of manganese atoms forming a φ and a θ angle, respectively with the X- and the Z-axis. At 4 K the magnetic moment of the Mn1 atom is μMn = 3.6(1) μB, with φ = 0° and θ = 62(4)°, whilst the Mn2 atom has a magnetic moment μMn = 3.6(1) μB, with φ = 0° and θ = 242(4)°. On the other hand, in this compound no local moment was detected on the Yb site. 相似文献
16.
The structural properties of the compounds in the tin-rich part of the dysprosium–tin system have been studied by X-ray powder diffraction. The crystal structures of six compounds DySn 2+x (0 < x < 1) have been characterized. There are four compounds with known structural types: DySn 2 with the ZrSi 2 structure, Dy 3Sn 7 with the Gd 3Sn 7 structure, Dy 2Sn 5 with the Er 2Ge 5 structure, DySn 3 with the DyGe 3 structure and two compounds characterized by new body-centred orthorhombic types ( Immm): Dy 5Sn 11 ( a = 4.411 Å, b = 42.50 Å and c = 4.328 Å) and Dy 5Sn 13 ( a = 4.341 Å, b = 48.05 Å and c = 4.405 Å) which result from various insertions of AuCu 3 and Po slabs into the ZrSi 2 structure. The relationships and structural evolution are discussed. 相似文献
17.
The subsolidus phase relation of the system ZnO–Li 2O–MoO 3 has been investigated by X-ray diffraction (XRD) analyses. The phase diagram has been constructed. There are six binary compounds and one ternary compound in this system. The phase diagram comprises nine three-phase regions. The ternary compound Li 2Zn 2(MoO 4) 3 is refined by the Rietveld method. It belongs to an orthorhombic system with space group Pnma and lattice constants a = 5.1114 Å, b = 10.4906 Å, c = 17.6172 Å. 相似文献
18.
Single crystals of KCr 0.8Al 0.2Mo 2O 8 were prepared and investigated by the X-ray diffractometer technique. It shows a structure type related to trigonal KAIMo 2O 8, monoclinic NaCrMo 2O 8 or orthorhombic KInMo 2O 8, space group C2h6— C2/ c; a=17.445 Å, b=5.649 Å, c=8.997 Å, β=119.37°; Z=4. KCr 0.8Al 0.2Mo 2O 8 is characterized by isolated MoO 4 tetrahedra, isolated (Cr/Al)O 6 octahedra and a distorted square antiprism around K +. The crystal structure is discussed with respect to those of related compounds. ZusammenfassungEinkristalle von KCr0.8Al0.2Mo2O8 wurden synthetisiert und mit Vierkreisdiffraktometertechnik röntgenographisch untersucht. Sie zeigen einen mit trigonal-KA1Mo2O8, monoklin-NaCrMo2O8 oder orthorhombisch-KlnMo2O8 verwandten Strukturtyp, Raumgruppe C2h6—C2/c; a=17,445 Å, b=5,649 Å, c=8,997 Å, β=119,37°; Z=4. KCr0.8Al0.2Mo2O8 zeichnet sich durch isolierte MoO4-Tetraeder, isolierte (Cr/Al)O6-Oktaeder und ein verzerrtes quadratisches Antiprisma um K+ aus. Die Kristallstruktur wird mit solchen verwandter Verbindungen diskutiert. 相似文献
19.
The subsolidus phase relationships of ternary system Na 2O–ZnO–WO 3 have been investigated by X-ray diffraction (XRD) and differential thermal analyzer (DTA). All the samples were synthesized in the temperature range from 530 to 850 °C in air. There are one ternary compound and five binary compounds in the Na 2O–ZnO–WO 3 system, which can be divided into eight three-phase regions. The crystal structure of the ternary compound Na 3.6Zn 1.2(WO 4) 3 is determined by single-crystal structure analysis method. It belongs to triclinic system with space group and lattice constants a = 7.237 (5) Å, b = 9.172 (6) Å, c = 9.339 (6) Å and = 94.920 (4)°, β = 105.772 (9)°, γ = 103.531 (8)°, Z = 2. DTA analyses indicate that the compound Na 2WO 4 is not suitable to be the flux for ZnO crystal growth below 1250 °C, since no liquidus was observed in the system before 1250 °C. 相似文献
20.
Subsequent magnetic transitions were recently reported for the CeScSi-type RScGe (R = rare earth) equiatomic intermetallic compounds. The compounds TbScGe and NdScGe order ferromagnetically at TC = 216 K and TC = 200 K, respectively whereas PrScGe orders antiferromagnetically at TN = 140 K. In addition, PrScGe demonstrates two other magnetic transitions at TC1 = 88 K and TC2 = 80 K in an applied field of 5 kOe. An investigation by neutron diffraction has been now carried out on these phases in an attempt to solve the magnetic structures corresponding to each ordering, and in this article the results obtained are reported. Below the Curie point, the magnetic structure of TbScGe and NdScGe is collinear ferromagnetic. The magnetic moment of Tb atoms coincides with the Z-axis of CeScSi-type unit cell ( MTb = 8.63 μB at 2 K), whereas the magnetic moment of Nd atoms has the θ = 52(2)° angle with Z-axis ( MNd = 3.53(2) μB at 2 K). Below the Néel temperature, TN = 140 K the magnetic structure of PrScGe consists of antiferromagnetic (0 0 2) rare-earth double layers with magnetic moments of the rare earth atoms collinearly ordered. The magnetic moments of Pr atoms ( MPr = 1.72(3) μB at 100 K) have the θ = 62(2)° angle with the Z-axis. Between TC1 = 82 K and TC2 = 62 K the conversion of the commensurate antiferromagnetic collinear type structure to the ferrimagnetic collinear type structure with propagation vector K = [0, 0, 1/2] was observed: the magnetic moments of Pr double layers became sine modulated along the Z-axis. Below TC2 = 62 K the magnetic structure of PrScGe compound consists of ferrimagnetic (0 0 1/2) layers (amplitude of Pr magnetic moment MPr = 3.31(9) μB at 5 K). 相似文献
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