Low temperature structural distortion in the high Tc Chevrel-phase superconductors PbMo6S8 and SnMo6S8

High-resolution powder neutron diffraction data reveal that, at temperatures below 100 K, oxygen-free, high-T_c samples of PbMo₆S₈ and SnMo₆S₈ exhibit a small structural distortion from the R$\text{3}$ rhombohedral space group. The data cannot be refined in a simple P$\text{1}$ triclinic space group as previously reported for EuMo₆S₈ and BaMo₆S₈. Thus, a supercell ordering is suggested.     

Magnetische struktur von columbiten MnTa2O6 und CoNb2O6

By means of neutron diffraction we found for MnTa₂O₆S₁S₂ S₃S₄ with a magnetic unit which is the same as the chemical. Whereas the chemical unit of CoNb₂O₆ is doubled in c-direction; all spins in the chemical unit are parallel. Therefore the orthorhombic symmetry of the crystal structure cannot be maintained. In both compositions are the spins parallel to the a-axis.     

Neutron diffraction study of the magnetic order in the ternary superconductor GdMo6S8

The coexistence of antiferromagnetism and superconductivity has been demonstrated in GdMo₆S₈ by neutron diffraction experiments. Although the magnetic unit cell (2a,a,a) is determined by the RKKY interactions, the direction of magnetic moments is determined by the anisotropic dipolar interactions i.e. in the (100) cubic plane.     

Direct observation of long range ferromagnetic order in the reentrant superconductor HoMo6S8

The neutron scattering technique has been used to investigate the magnetic properties of the ternary Chevrel-phase superconductor HoMo₆S₈. Magnetic critical scattering is observed in the superconducting phase, with the magnetic correlation range increasing with decreasing temperature. At the transition in which the normal state is reentered, the system is found to develop long range ferromagnetic order, with a saturated magnetic moment at low temperatures of 9.06 ± .3 μ_B and the spin direction along the unique [111] trigonal axis.     

Chevrel相MxMo6S8化合物电荷转移和Mo原子上4d轨道能级的分裂

本文用配位场方法导出了Chevrel相M_xMo₆S₈化合物中M和Mo₆S₈原子簇间电荷转移和Mo原子上4d轨道能级分裂的解析关系。结合PbMo₆S₈的反射光谱,求得Mo₆S₈原子簇至Pb的电子转移数为1.18,和以前一般文献上认为的两个电子从Pb转移至Mo₆S₈不同。Mo₆上的4d电子数为18.8。 关键词：     

Magnetic ordering in the superconducting state of rare earth molybdenum sulphides, (RE)1.2Mo6S8 (RE = Tb, DyandEr)

The resistance and ac susceptibility measurements on Tb_1.2Mo₆S₈, Dy_1.2Mo₆S₈ and Er_1.2Mo₆S₈ revealed a magnetic ordering in their superconducting state at 0.9, 0.4 and 0.15 K, respectively. Some of the important features of the ordering in each compound are discussed with reference to their upper critical field curves.     

Magnetic structure of V5S8

The magnetic structure of V₅S₈ has been investigated by neutron diffraction at low temperature. Two single crystals (sample 1 and sample 2) grown by the same procedure gave considerably different results. Sample 1 was found to have an incommensurate structure, while sample 2 was found to have simple collinear antiferromagnetic structure consistent with magnetic measurements. Although the positions of the magnetic diffraction peaks of sample 1 were close to those of sample 2, the neutron intensity behavior was quite different and the detailed structure could not be determined in the case of sample 1. In both samples, the magnitude of the moments was evaluated to be much larger than the value estimated from NMR.     

Salting-out in intercalation compounds: Removing copper from Cu3Mo6S8 by intercalating lithium

We study the removal of the copper in Cu₃Mo₆S₈ by the intercalation of lithium. For 0<×<1, Li_xCu₃Mo₆S₈ is a single phase compound. For x?1, the copper atoms are forced out of the Mo₆S₈ host. We present a lattice-gas model which shows how the intercalation of Li can force the Cu out of the host.     

Superconductivity in the RexMo6S8

The rare earth molybdenum sulfides RE_xMo₆S₈ (RE = rare earth) have been synthesized and are found to be superconducting with a few exceptions. This result, which is surprising in view of the high concentration of magnetic ions, is correlated with the particular structure of these compounds based on on units of Mo₆S₈.     

Neutron inelastic scattering study of exchange interactions in a ruthenium V dimer a3CaRu2O9

Inelastic neutron scattering measurements have been performed on the binuclear Ru(V) cluster compound Ba₃CaRu₂O₉. The S = 0 →S = 1 transition split levels of the electronic ground state has been observed. The value for the exchange parameter is very close to that obtained from magnetic susceptibility measurements. The observed intensity ratios of the neutron inelastic scattering transition agree well with those calculated from a simple spin-spin coupling model for the ruthenium pair.     

Synthesis and physical properties of new superconducting Chevrel phases HgxMo6S8

New ternary molybdenum chalcogenides Hg_xMo₆S₈ (0 < x < 1) have been synthesized and investigated for their structural, magnetic, and superconducting behavior. These new phases prepared at low temperature by reaction of mercury with Mo₆S₈ (obtained from oxidation of Cu₂Mo₆S₈ by iodine) have been characterized by x-ray diffraction, static Faraday susceptibility, and superconducting transition temperature studies. HgMo₆S₈ crystallizes in the rhombohedral space group $\text{R}\text{3 (}\text{a}{}_{\mathrm{r}}\text{= 6.51}\text{A}\text{?}\text{, α}{}_{\mathrm{<mtext>r</mtext>}}\text{= 92.53°)}$, has a paramagnetic, temperature dependent susceptibility, and superconducts at 8.1K. As the mercury content decreases, a continuous decrease in T_c from 8.1K to 1.7K for x=0 (Mo₆S₈) is observed.     

Preparation and mass transport properties of Li2.3Mo6S7.7

Unsuccessful attempts were made to prepare Li_xMo₆S_7.7 by direct ionic exchange of Cu₂Mo₆S_7.7 using aqueous, acetontrille, and molten salt solvents. Li_2.3Mo₆S_7.7 was eventually prepared by lithiation of Mo₆S₈ using n-butyl lithium reagent. The mass transport properties of hot-pressed samples were measured using a four-point dc technique and the following values at 415°C for the lithium ionic conductivity, .4×10⁻⁴ (ohms cm⁻¹) and lithium chemical diffusion coefficient 3.5×10⁻⁷ cm²/s, were derived. A possible explanation for the relatively low lithium ion mobility in Li_2.3Mo₆S_7.7 is discussed.     

MAGNETIC FIELD EFFECT OF THE EUROPIUM a8S7/2-z6P7/2 LINES

The magnetic field effect of a⁸S_7/2-z⁶P_7/2 lines of ¹⁵¹Eu and ¹⁵³Eu in magnetic fields up to 66.7 mT has been studied by using laser atomic beam spectroscopy. The Zeeman level structures of the europium a⁸S_7/2 and z⁶P_7/2 states in magnetic fields were discussed. The location and intensity of the measured Zeeman transition lines were found in good agreement with the theoretical results.     

铯6S1/2 -6P3/2 -8S1/2阶梯型系统中超精细能级的多重电磁感应透明

基于铯原子6S_1/2 -6P_3/2 -8S_1/2的阶梯型能级系统,对室温下铯原子气室中的电磁感应透明(EIT)谱进行了研究.由于探测光的频率锁定于基态6S_1/2(F=3)到中间态6P_3/2的超精细跃迁线上,耦合光在中间态6P_3/2和激发态8S_1/2之间扫描,得到的EIT谱具有平坦的背景,提高了光谱的精度.理论上,采用了一个多能级的EIT模型,将其计算结果与所观察的实验现象进行了比较,二者符合得比较好. 关键词： 电磁感应透明 光抽运 超精细结构 阶梯型系统     

Coulometric titration of copper in CuxMo6S8−y(0⩽y⩽0.4) with solid Cu-electrolyte Rb4Cu16I7Cl13

In order to determine the copper content x of copper Chevrel compound Cu_xMo₆S_8?y(0?y?0.4) as a function of copper activity a_Cu and sulfur deficit y, a solid state electrochemical cell, Cu/Rb₄Cu₁₆I₇Cl₁₃/Cu_xMo₆S_8?y/Pt, was constructed and coulometric titration studies were made at 400 K. For the evaluation of the coulometric titration data, measurements were made on the electronic conductivity of copper-ion conductor Rb₄Cu₁₆I₇Cl₁₃. Also, a brief investigation was made on the condition of formation of single phase Chevrel Cu_xMo₆S_8?y with varying x and y at 1000°C. The structural change of Cu_xMo₆S_8?y with a change in x and y was studied by the X-ray diffraction method. It was found that x for constant a_Cu decreases with increasing y. The maximum value x_max of x in Cu_xMo₆S_8?y in equilibrium with metallic copper was found to be expressed by $\text{x}{}_{\mathrm{<mtext>max</mtext>}}\text{=-(}\text{10}\text{3}\text{)y+5}$. In the region of y<0.3, x_max exceeded 4, contrary to a presupposition that x_max is less than 4. X-ray analysis revealed that most of the copper Chevrel compounds denoted by Cu_xMo₆S₈ so far were sulfur deficient ones with y?0.4. The importance of sulfur deficit on the properties of the copper Chevrel compound was emphasized.     

Spin structure and magnetic anisotropy of Cr5S6 and rhombohedral Cr2S3

The magnetic properties of single crystals of rhombohedral Cr₂S₃ have been measured. The data indicate a preferred orientation of the spins of the Cr atoms in a plane perpendicular to the trigonal axis. New neutron diffraction data for powdered samples which confirm this conclusion are presented.     

反应扩散法制备的PbMo6S8超导带的超导特性

本文报道反应扩散法制备Chevrel相PbMo₆S₈超导带材的过程以及带材的超导特性。Mo带与H₂S气体反应生成单相的Mo-S化合物(MoS₂或Mo₂S₃,根据反应温度而定),再与Pb的蒸汽反应生成单相的PbMo₆S₈薄层。PbMo₆S₈超导层的临界温度T_c=13.0 关键词：     

Critical currents of LaMo6S8 thin films

The thin films of LaMo₆S₈ were prepared by d.c. getter sputtering method. Critical current have been measured vs applied magnetic field B_⊥ up to 8 T at the temperature ranged from 1.7 to 4.2 K. The highest critical current density reached was J_c = 1.7 × 10⁷ Am^?2 at B = 0 and T = 1.7 K. Based on the measurements performed, it was possible to indicate that depending on the heat treatment applied, the pinning forces created in the LaMo₆S₈ thin films obey the scaling law.     

非晶态合金Co81.5B18.5结构的研究

本文叙述了用X射线衍射方法及偏振中子衍射方法对Co_81.5B_18.5非晶合金的结构研究。利用两种数据处理方法,从实验结果中计算了Co_81.5B_18.5的偏干涉函数(PSF),S_ij(Q),和偏简约径向分布函数G_ij(r)。并对这两种结果作了比较。最后计算了一种模型简单单元的中子衍射散射强度,并讨论了这一非晶合金的结构模型。 关键词：     

Absence of hydrogen in superconducting molybdenum sulfide,Mo3S4

Superconducting Mo₃S₄(T_c=1.8 K) was prepared from the ternary sulfides MMo₃S₄ (M=Cu, Ni) by the acid extraction method, and was studied by neutron diffraction and NMR spectroscopy. In contrast to earlier reports no significant amounts of hydrogen could be found in the rhombohedral structure. However, large proton concentrations were found in samples which had been exposed to moist air.