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1.
The ternary intermetallic compounds RE2Cu2Cd (RE=Y, Sm, Gd-Tm, Lu) were synthesized by induction-melting of the elements in sealed tantalum tubes. The samples were characterized by X-ray powder diffraction. The structure of Gd2Cu2Cd was refined from single crystal X-ray diffractometer data: Mo2FeB2 type, space group P4/mbm, a=756.2(3), c=380.2(3) pm, wR2=0.0455, 321 F2 values, 12 variables. The structures are 1:1 intergrowth variants of slightly distorted CsCl and AlB2 related slabs of compositions RECd and RECu2. The copper and cadmium atoms build up two-dimensional [Cu2Cd] networks (257 pm Cu-Cu and 301 pm Cu-Cd in Gd2Cu2Cd) which are bonded to the rare earth atoms via short RE-Cu contacts (290 pm in Gd2Cu2Cd). Temperature dependent susceptibility measurements of RE2Cu2Cd with RE=Gd, Tb, Dy, and Tm show experimental magnetic moments which are close to the free RE3+ ion values. The four compounds show ferromagnetic ordering at TC=116.7(2), 86.2(3), 48.4(1), and 14.5(1) K, respectively, as confirmed by heat capacity measurements. Dy2Cu2Cd shows a spin reorientation at TN=16.9(1) K.  相似文献   

2.
A new family of quaternary carbon and nitrogen containing Rare Earth (RE: Sc, Y, Ho, Er, Tm and Lu) borides: REB15.5CN, has been synthesized and structurally characterized by powder X-ray diffraction data. They are all isotypic with Sc1−xB15.5CN whose structure was solved based on single-crystal X-ray data and HRTEM investigations. The structure refinement converged at a R(F2) value of 0.044 for 364 reflections. The new structure type of Sc1−xB15.5CN is composed of a three-dimensional network based on interconnected slabs of boron (B12)ico icosahedra and (B6)oct octahedra. A linear [CBC] chain and nitrogen tightly bridges icosahedra. Sc partially occupies voids in the sheets of boron octahedra. It crystallizes with the trigonal space group P3m1, with Z=2. Lattice parameters (nm) are as follows: for RE: Sc, a,b=0.5568(4), c=1.0756(2); Y, a,b=0.55919(6), c=1.0873(2); Ho, a,b=0.55883(7), c=1.0878(6); Er, a,b=0.55889(5), c=1.0880(6); Tm, a,b=0.5580(1), c=1.0850(6); Lu, a,b=0.55771(9), c=1.0839(4). Magnetic characterization of ErB17C1.3N0.6 has been performed.  相似文献   

3.
The magnetic behavior of the ternary borides RE2RuB6 and RE2OsB6 (RE = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) was studied in the temperature range 1.5 K < T < 1100 K. All compounds crystallize with the Y2ReB6-type structure and are characterized by direct RE-RE contacts and the formation of planar infinite two-dimensional rigid boron nets. The magnetic properties reveal a typical Van Vleck paramagnetism of free RE3+-ions at temperatures higher than 200 K with ferromagnetic interaction in the low-temperature range T < 55 K. The ferromagnetic ordering temperatures vary with the De Gennes factor. There is no indication for a magnetic contribution from the Ru(Os)-sublattice. Above 1.8 K none of the samples were found to be superconducting.  相似文献   

4.
A series of ternary compounds RECu9Mg2 (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb) have been synthesized via induction melting of elemental metal ingots followed by annealing at 400 °C for 4 weeks. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS) was used for examining microstructure and phase composition. These phases crystallize with an ordered version of the binary hexagonal structure type first reported for CeNi3. The crystal structure was solved for TbCu9Mg2 from single crystal X-ray counter data (TbCu9Mg2-structure type, P63/mmc-space group, hP24-Pearson symbol, a=0.49886 (7) nm, c=1.61646 (3) nm, RF=0.0474 for 190 unique reflections). The Rietveld refinement of the X-ray powder diffraction patterns of RECu9Mg2 confirmed the same crystal structure for the reported rare earth metals. The unit cell volumes for RECu9Mg2 smoothly follow the lanthanide contraction. The existence of a RECu9Mg2 phase was excluded for RE=Er and Tm under the investigated experimental conditions.  相似文献   

5.
Three rare earth borosilicate oxyapatites, RE5Si2BO13 (RE=La, Gd, Y), were synthesized via wet chemical method, of which RE5Si2BO13 (RE=Gd, Y) were first reported in this work. In the three oxyapatites, [BO4] and [SiO4] share the [TO4] tetrahedral oxyanion site, and RE3+ ions occupy all metal sites. The differential scanning calorimetry-thermo gravimetry measurements and high temperature powder X-ray diffraction pattern revealed a vitrification process within 300-1200 °C, which was due to the glass-forming nature of borosilicates. From the VUV excitation spectra of Eu3+ and Tb3+ in RE5Si2BO13, the optical band gaps were found to be 6.31, 6.54 and 6.72 eV for RE5Si2BO13 (RE=La, Gd, Y), respectively. The emission and excitation bands of Eu3+ and Tb3+ are discussed relating with their coordination environments. Among the three hosts, Y5Si2BO13 would be the best for Eu3+ and Tb3+-doped phosphors.  相似文献   

6.
Four new isostructural rare earth manganese stannides, namely RE3MnSn5−x (x=0.16(6), 0.29(1) for RE=Tm, x=0.05(8), 0.21(3) for RE=Lu), have been obtained by reacting the mixture of corresponding pure elements at high temperature. Single-crystal X-ray diffraction studies revealed that they crystallized in the orthorhombic space group Pnma (No. 62) with cell parameters of a=18.384(9)-18.495(6) Å, b=6.003(3)-6.062(2) Å, c=14.898(8)-14.976(4) Å, V=1644.3(14)-1679.0(9) Å3 and Z=8. Their structures belong to the Hf3Cr2Si4 type and feature a 3D framework composed of 1D [Mn2Sn7] chains interconnected by [Sn3] double chains via Sn-Sn bonds, forming 1D large channels based on [Mn4Sn16] 20-membered rings along the b-axis, which are occupied by the rare earth atoms. Electronic structure calculations based on density functional theory (DFT) for idealized “RE3MnSn5” model indicate that these compounds are metallic, which are in accordance with the results from temperature-dependent resistivity measurements.  相似文献   

7.
Investigations on phase relationships and crystal structures have been conducted on several ternary rare-earth titanium antimonide systems. The isothermal cross-sections of the ternary RE-Ti-Sb systems containing a representative early (RE=La) and late rare-earth element (RE=Er) have been constructed at 800 °C. In the La-Ti-Sb system, the previously known compound La3TiSb5 was confirmed and the new compound La2Ti7Sb12 (own type, Cmmm, Z=2, a=10.5446(10) Å, b=20.768(2) Å, and c=4.4344(4) Å) was discovered. In the Er-Ti-Sb system, no ternary compounds were found. The structure of La2Ti7Sb12 consists of a complex arrangement of TiSb6 octahedra and disordered fragments of homoatomic Sb assemblies, generating a three-dimensional framework in which La atoms reside. Other early rare-earth elements (RE=Ce, Pr, Nd) can be substituted in this structure type. Attempts to prepare crystals in these systems through use of a tin flux resulted in the discovery of a new Sn-containing pseudoternary phase RETi3(SnxSb1−x)4 for RE=Nd, Sm (own type, Fmmm, Z=8; a=5.7806(4) Å, b=10.0846(7) Å, and c=24.2260(16) Å for NdTi3(Sn0.1Sb0.9)4; a=5.7590(4) Å, b=10.0686(6) Å, and c=24.1167(14) Å for SmTi3(Sn0.1Sb0.9)4). Its structure consists of double-layer slabs of Ti-centred octahedra stacked alternately with nets of the RE atoms; the Ti atoms are arranged in kagome nets.  相似文献   

8.
Using Na2CO3-H3BO3-NaF as fluxes, transparent RE:Na3La9O3(BO3)8 (abbr. RE:NLBO, RE=Er, Yb) crystals have been grown by the top seed solution growth (TSSG) method. The X-ray powder diffraction analysis shows that the RE:NLBO crystals have the same structure with NLBO. The element contents were determined by molar to be 0.64% Er3+ in Er:NLBO, 2.70% Yb3+ in Yb:NLBO, respectively. The polarized absorption spectra of RE:NLBO have been measured at room temperature and show that both Er:NLBO and Yb:NLBO have a strong absorption bands near 980 nm with wide FWHM (Full Wave at Half Maximum) (21 nm for Er:NLBO and 25 nm for Yb:NLBO). Fluorescence spectra have been recorded. Yb:NLBO has the emission peaks at 985 nm, 1028 nm and 1079 nm and the emission peak of Er:NLBO is at 1536 nm. Spectral parameters have been calculated by the Judd-Ofelt theory for Er:NLBO and the reciprocity method for Yb:NLBO, respectively. The calculated values show that Er:NLBO is a candidate of 1.55 μm laser crystals and Yb:NLBO is a candidate for self-frequency doubling crystal.  相似文献   

9.
The rare earth metal rich compounds RE4NiMg (RE=Y, Pr-Nd, Sm, Gd-Tm, Lu) were synthesized from the elements in sealed tantalum tubes in an induction furnace. All compounds were investigated by X-ray diffraction on powders and single crystals: Gd4RhIn type, space group F4¯3m, Z=16, a=1367.6(2) pm for Y4NiMg, a=1403.7(3) pm for Pr4NiMg, a=1400.7(1) pm for Nd4NiMg, a=1386.5(2) pm for Sm4NiMg, a=1376.1(2) pm for Gd4NiMg, a=1362.1(1) pm for Tb4NiMg, a=1355.1(2) pm for Dy4NiMg, a=1355.2(1) pm for Ho4NiMg, a=1354.3(2) pm for Er4NiMg, a=1342.9(3) pm for Tm4NiMg, and a=1336.7(3) pm for Lu4NiMg. The nickel atoms have trigonal prismatic rare earth coordination. These NiRE6 prisms are condensed via common edges to a three-dimensional network which leaves voids for Mg4 tetrahedra and the RE1 atoms which show only weak coordination to the nickel atoms. The single crystal data indicate two kinds of solid solutions. The RE1 positions reveal small RE1/Mg mixing and some compounds also show Ni/Mg mixing within the Mg4 tetrahedra. Y4NiMg and Gd4NiMg have been tested for hydrogenation. These compounds absorb up to eleven hydrogen atoms per formula unit under a hydrogen pressure of 1 MPa at room temperature. The structure of the metal atoms is maintained with only an increase of the lattice parameters (ΔV/V≈22%) if the absorption is done at T<363 K as at higher temperature a decomposition into REH2-REH3 hydrides occurred. Moreover, the hydrogenation affects drastically the magnetic properties of these intermetallics. For instance, Gd4NiMg exhibits an antiferromagnetic behavior below TN=92 K whereas its hydride Gd4NiMgH11 is paramagnetic down to 1.8 K.  相似文献   

10.
Large single crystals from RENi2-xP2 (RE=La, Ce, Pr) were synthesized from the pure elements using Sn as a metal flux, and their structures were established by X-ray crystallography. The title compounds were confirmed to crystallize in the body-centered tetragonal ThCr2Si2 structure type (space group I4/mmm (No. 139); Pearson's symbol tI10), but with a significant homogeneity range with respect to the transition metal. Systematic synthetic work, coupled with accurate structure refinements indicated strong correlation between the degree of Ni-deficiency and the reaction conditions. According to the temperature dependent dc magnetization measurements, LaNi2-xP2 (x=0.30(1)), as expected, is Pauli-like paramagnetic in the studied temperature regime, while the Ce-analog CeNi2-xP2 (x=0.28(1)) shows the characteristics of a mixed valent Ce3+/Ce4+ system with a possible Kondo temperature scale on the order of 1000 K. For three different PrNi2-xP2 (x?0.5) samples, the temperature and field dependence of the magnetization indicated typical local moment 4f-magnetism and a stable Pr3+ ground state, with subtle variations of TC as a function of the concentration of Ni defects. Field-dependent heat capacity data for CeNi2-xP2 (x=0.28(1)) and PrNi2-xP2 (x=0.53(1)) are discussed as well.  相似文献   

11.
The RE3Ga9Ge compounds (RE=Y, Ce, Sm, Gd and Yb) were synthesized at 850°C in quantitative yield from reactions containing excess liquid Ga. The orthorhombic crystal structure is characterized by a unique three-dimensional open Ga framework with parallel straight tunnels. In the tunnels, inserted are arrays of the RE atoms together with interpenetrated monoatomic RE-Ga-Ge planes. A complex disordered arrangement of the RE and Ga atoms is observed in the monoatomic plane. Depending on the extent of disorder, the crystal structure could be presented either in a sub-cell (no ordering) or in a super-cell (partial ordering). Single-crystal X-ray data for Ce3Ga9Ge sub-structure: space group Immm, Z=2, cell parameters a=4.3400(12) Å; b=10.836(3) Å; and c=11.545(3) Å; super-structure: space group Cmma, Z=8, cell parameters a=8.680(3) Å; b=23.090(7) Å; and c=10.836(3) Å. The refinement based on the full-matrix least squares on Fo2[I>2σ(I)] converged to final residuals R1/wR2=0.0226/0.0528 and 0.0729/0.1569 for the sub- and super-structures, respectively. The relationship between the disordered sub-structure and partially ordered super-structure is discussed. Magnetic susceptibility measurements show Curie-Weiss behavior at the temperatures above 30 K with the negative Weiss constants Θ=−49(1) and−7.7 K for Gd and Ce analogs, respectively. An antiferromagnetic transition is observed in the Gd analog at TN=26.1 K. The μeff obtained for both analogs is close to the RE3+ free-ion value.  相似文献   

12.
This work reports the preparation of system containing RE2+ ions (RE=Sm and Eu)-doped in SrB4O7 matrix by ceramic, Pechini and combustion methods. These compounds were prepared by reduction of RE3+ to RE2+ in air, which exhibit some different features according to the preparation method. Photoluminescent properties of these systems were investigated based on the emission and excitation spectral data. The emission spectra of SrB4O7:Eu2+ system prepared by combustion and Pechini methods are characterized by a broad band assigned to interconfigurational 4f65d→4f7 transition, while SrB4O7:Sm2+ compound exhibit narrow emission bands arising from intraconfigurational-4f6 also shows 4G5/26HJ′ transitions ( and ) arising from Sm3+ ion, transitions. SrB4O7:RE system prepared by combustion method presents emission bands from RE3+ ions as intense as that arising from RE2+, suggesting that the preparation route is not efficient for the reduction RE3+RE2+ process. Emission quantum efficiency and radiative emission rates of Sm2+ ion are determined and discussed.  相似文献   

13.
Physical properties of a series of homologous RE-B-C(N) B12 cluster compounds REB17CN, REB22C2N, and were investigated. The structures of the compounds are layer-like along the c-axis, with rare earth and B6 octahedral layers separated by B12 icosahedral and C-B-C chain layers whose number increases successively from two B12 layers for the REB17CN compound to four for the REB28.5C4 compound. The rare earth atoms are configured in two triangular flat layers which are stacked on top of one another in AB stacking where the nearest-neighbor rare earth directions are the three atoms forming a triangle in the adjacent layer. The series of homologous compounds exhibit a spin glass transition with Tf shifting in correspondence with variations of the basal plane lattice constants, consistent with the magnetic interaction being effective in the basal planes. The isothermal remanent magnetization shows a stretched exponential decay . Exponents determined for the different homologous compounds were scaled as a function of Tr=T/Tf and found to follow the empirical dependency determined for typical spin glasses. It is indicated that a mixture of disorder originating from the partial occupancy of the rare earth sites and frustration of interactions due to the unique configuration is responsible for the manifestation of spin glass transitions in these homologous systems.  相似文献   

14.
Application of high-pressure high-temperature conditions (3.5 GPa at 1673 K for 5 h) to mixtures of the elements (RE:B:S=1:3:6) yielded crystalline samples of the isotypic rare earth-thioborate-sulfides RE9[BS3]2[BS4]3S3, (RE=Dy-Lu), which crystallize in space group P63 (Z=2/3) and adopt the Ce6Al3.33S14 structure type. The crystal structures were refined from X-ray powder diffraction data by applying the Rietveld method. Dy: a=9.4044(2) Å, c=5.8855(3) Å; Ho: a=9.3703(1) Å, c=5.8826(1) Å; Er: a=9.3279(12) Å, c=5.8793(8) Å; Tm: a=9.2869(3) Å, c=5.8781(3) Å; Yb: a=9.2514(5) Å, c=5.8805(6) Å; Lu: a=9.2162(3) Å, c=5.8911(3) Å. The crystal structure is characterized by the presence of two isolated complex ions [BS3]3- and [BS4]5- as well as [□(S2-)3] units.  相似文献   

15.
The rare earth-nickel-indides RE14Ni3In3 (RE=Sc, Y, Gd-Tm, Lu) were synthesized from the elements by arc-melting and subsequent annealing. The compounds were investigated on the basis of X-ray powder and single crystal data: Lu14Co2In3 type, P42/nmc, Z=4, a=888.1(1), c=2134.7(4), wR2=0.0653, 1381 F2 values, 63 variables for Sc13.89Ni3.66In2.45; a=961.2(1), c=2316.2(5), wR2=0.0633, 1741 F2 values, 64 variables for Y13.84Ni3.19In2.97; a=965.3(1), c=2330.5(5), wR2=0.0620, 1765 F2 values, 63 variables for Gd14Ni3.29In2.71; a=956.8(1), c=2298.4(5), wR2=0.0829, 1707 F2 values, 64 variables for Tb13.82Ni3.36In2.82; a=951.7(1), c=2289.0(5), wR2=0.0838, 1794 F2 values, 64 variables for Dy13.60Ni3.34In3.06; a=948.53(7), c=2270.6(1), wR2=0.1137, 1191 F2 values, 64 variables for Ho13.35Ni3.17In3.48; a=943.5(1), c=2269.1(5), wR2=0.0552, 1646 F2 values, 64 variables for Er13.53Ni3.14In3.33; a=938.42(7), c=2250.8(1), wR2=0.1051, 1611 F2 values, 64 variables for Tm13.47Ni3.28In3.25; a=937.3(1), c=2249.6(5), wR2=0.0692, 1604 F2 values, 64 variables for Tm13.80Ni3.49In2.71; and a=933.4(1), c=2263.0(5), wR2=0.0709, 1603 F2 values, 64 variables for Lu13.94Ni3.07In2.99. The RE14Ni3In3 indides show significant Ni/In mixing on the 4c In1 site. Except the gadolinium compound, the RE14Ni3In3 intermetallics also reveal RE/In mixing on the 4c RE1 site, leading to the refined compositions. Due to the high rare earth metal content, the seven crystallographically independent RE sites have between 9 and 10 nearest RE neighbors. The RE14Ni3In3 structures can be described as a complex intergrowth of rare earth-based polyhedra. Both nickel sites have a distorted trigonal-prismatic rare earth coordination. An interesting feature is the In2-In2 dumb-bell at an In2-In2 distance of 304 pm (for Gd14Ni3.29In2.71). The crystal chemical peculiarities of the RE14Ni3In3 indides are briefly discussed.  相似文献   

16.
The quaternary rare-earth phosphides RECuZnP2 (RE=Pr, Nd, Gd-Tm, Lu) have been prepared by reaction of the elements at 900 °C, completing this versatile series which forms for nearly all RE metals. They adopt the trigonal CaAl2Si2-type structure (Pearson symbol hP5, space group P3?m1, Z=1), as confirmed by single-crystal X-ray diffraction analysis on ErCuZnP2 and powder X-ray diffraction analysis on the remaining members. The Cu and Zn atoms are assumed to be disordered over the single transition-metal site. Band structure calculations on a hypothetically ordered YCuZnP2 model suggest a semimetal, with a zero band gap between the valence and conduction bands. This electronic structure is supported by XPS valence band spectra for RECuZnP2 (RE=Gd-Er), in which the intensity drops off smoothly at the Fermi edge. The absence of a band gap permits the electron count to deviate from the precise value of 16 e per formula unit, as demonstrated by the formation of a solid solution in GdCuxZn2−xP2 (1.0≤x≤1.3), while still retaining the CaAl2Si2-type structure. Because the Cu 2p XPS spectra indicate that the Cu atoms are always monovalent, the substitution of Cu for Zn leads to a decrease in electron count and a lowering of the Fermi level in the valence band. The magnetic susceptibility of RECuZnP2 (RE=Gd-Er), which obeys the Curie-Weiss law, confirms the presence of trivalent RE atoms.  相似文献   

17.
Single crystals of K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K3RESi2O7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K3LuSi2O7, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K3LuSi2O7 crystallizes in space group P63/mmc with a=5.71160(10) Å and c=13.8883(6) Å. The structures containing the remaining rare earths crystallize in the space group P63/mcm with the lattice parameters of a=9.9359(2) Å, c=14.4295(4) Å, (K3GdSi2O7); a=9.88730(10) Å, c=14.3856(3) Å, (K3TbSi2O7); a=9.8673(2) Å, c=14.3572(4) Å, (K3DySi2O7); a=9.8408(3) Å, c=14.3206(6) Å, (K3HoSi2O7); a=9.82120(10) Å, c=14.2986(2) Å, (K3ErSi2O7); a=9.80200(10) Å, c=14.2863(4) Å, (K3TmSi2O7); a=9.78190(10) Å, c=14.2401(3) Å, (K3YbSi2O7). The optical properties of the silicates were investigated and K3TbSi2O7 was found to fluoresce in the visible.  相似文献   

18.
A series of compositions with the general formula RE2Hf2O7 (RE=Dy, Ho, Er, Tm, Y and Lu) was prepared by a standard solid-state route and characterized by powder X-ray diffraction (XRD) and Raman spectroscopy. As per theoretical modeling reported in literature, some of these materials were predicted to exist in pyrochlore lattice. However, a careful X-ray diffraction, Raman spectroscopic and synchrotron radiation-XRD study revealed that under the experimental conditions used in the present investigation, out of all the RE2Hf2O7 samples only Dy2Hf2O7 has got a tendency to form a pyrochlore structure. All the other (Ho, Er, Tm, Lu, Y) hafnates crystallize in a defect-fluorite structure. In order to further ascertain these inferences, a few more RE2Hf2O7 samples (La, Nd, Sm) i.e., with larger RE3+ ions were also prepared and the results were compared.  相似文献   

19.
The ternary rare-earth zinc antimonides REZn1-xSb2 (RE=La, Ce, Pr, Nd, Sm, Gd, Tb) were prepared by heating at 1050 °C followed by annealing at 600 °C. For all members, single-crystal X-ray diffraction studies indicated that the Zn deficiency is essentially fixed, corresponding to the formula REZn0.6Sb2, with no appreciable homogeneity range. These compounds adopt the HfCuSi2-type structure (Pearson symbol tP8, space group P4/nmm, Z=2). Single-crystal electrical resistivity measurements confirmed the occurrence of an abrupt resistivity decrease near 4 K for RE=Ce, and a less pronounced one for RE=La, Pr, and Gd. Except for the ferromagnetic Ce (Tc=2.5 K) and antiferromagnetic Tb (TN=10 K) members, all remaining compounds exhibit no long-range magnetic ordering down to 2 K, instead showing temperature-independent (RE=La), van Vleck (RE=Sm), or Curie-Weiss paramagnetism (RE=Pr, Nd, Gd).  相似文献   

20.
The ternary rare-earth metal silicide borides RE5Si2B8 (RE=Y, Sm, Gd, Tb, Dy Ho) were prepared by arc melting the elemental components and subsequent annealing up to . The crystal structure was determined for each term of the series from single-crystal X-ray data: tetragonal symmetry, space group P4/mbm, Z=2; unit cell parameters a=7.2616(3), and a=7.1830(2), for Sm5Si2B8 and Ho5Si2B8, respectively. The structure is a new type and can be structurally described as an intergrowth of ThB4-like and U3Si2-like slabs of composition REB4 and RE3Si2, respectively, alternating along the c direction. The boron and silicon substructures are wholly independent and well ordered. The magnetic properties are as follows: Y5Si2B8 is a Pauli-type paramagnet above 1.8 K, Gd5Si2B8 undergoes a weak (canted) ferromagnetic-like order at 70 K followed by a colinear antiferromagnetic spin alignment at 44 K. Tb5Si2B8 and Dy5Si2B8 order antiferromagnetically at a Néel temperature of TN=45 and 28 K, respectively. In the paramagnetic regime, the effective moments are in good accord with the theoretical RE3+ free ion moments. The temperature dependence of the electrical resistivities for the Y, Gd, Tb, and Dy containing samples corroborates with the metallic state of the nonmagnetic (Y) and the magnetically ordered compounds. 11B, 29Si and 89Y nuclear magnetic resonance (NMR) spectroscopy on nonmagnetic Y5Si2B8 shows different signals, which correspond to the expected number of distinct crystallographic sites in the structure. 11B NMR on Y5Si2B8 indicates that the local magnetic susceptibilities are substantially different from the ones observed in the related compound YB4.  相似文献   

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