On the hexadecapole anomaly at the border of the rare earth region

Theoretical calculations of equilibrium deformations and multipole moments of rare earth nuclei are presented. Good agreement with experiment for the centre of the rare earth region is found, but there are large discrepancies for the heavy Hf, W and Os isotopes and some light Sm and Gd nuclei. These discrepancies are related to hexadecapole moments and deformations. The assumption of a “partial bubble” like density distribution, as suggested by electron scattering measurements, is found to be insufficient to explain this hexadecapole anomaly. The inclusion of non-axial and hexadecapole degrees of freedom in processing the experimental data, as well as in performing theoretical calculations, is found to be the most promising approach to explaining the hexadecapole anomaly.     

Thermal expansion and relaxation of magnetostriction in a metastable state of dysprosium orthoaluminate

A study of thermal expansion and magnetostriction caused by the metamagnet phase transition in a rare earth sublattice was performed for a DyAlO₃ single crystal, which is the model object of a wide family of rare earth oxides with the structure of distorted perovskite. The sharp variation of the relative strains along the b axis 3.6 × 10⁻⁵ was found at T ≌ 2.18 K. The nature of the observed anomaly is caused by the occurrence of a metastable state of the magnetic subsystem achieved in the conditions of the experimental process. The relaxation of magnetostriction is studied and the exponential character is found. The possible mesoscopic nature of thermal and quantum mechanisms of magnetic relaxation is considered.     

X-ray isochromats of some rare earth elements

Recordings of the isochromat curves of the rare earth elements 64 Gd to 71 Lu have been made by means of a high vacuum spectrometer provided with a bent topaz crystal. The information concerning the density of statesN(E) near the Fermi limit is compared with that deduced from specific heat measurements. The results obtained from the isochromat curves are rather constant, which on account of the atomic configuration in these elements is expected. An observed anomaly in the band structure of Tb metal is discussed. The appearance of this anomaly indicates that a rigid band model is not applicable to some of the actual elements.     

Rare Earth Photoluminescence in Bismuth-Germanate Crystals

In the present work, the photoluminescence (PL) spectra of bismuth germanate (BGO) doped with trivalent rare earth element (REE) ions with different doping concentrations (0.03 wt% Eu, 0.4 wt% Tm, and 1.1 wt% Nd) are reported in the temperature range from 10 to 300 K using different detectors, namely, photomultiplier tube (PMT), InGaAs (IGA), and Si. The luminescence in the NIR region was also measured at room temperature. Two broad emission bands attributed to undoped BGO were found at circa 1350 and 1800 nm, respectively. The broad-band emissions are replaced by narrow-band line emissions defined by the trivalent rare earth dopants. The emission spectra from rare earth ion–doped BGO extend from 500 to 2000 nm. Rare earth ions act as the dominant recombination centers and define the emission spectra. This is interpreted as resulting from direct charge transfer from intrinsic defect traps to rare earth recombination centers. The temperature-dependent luminescence of BGO doped with 0.4 wt% Tm is also presented.     

热致可逆变色的聚二炔/稀土离子纳米复合物

将Dy⁺或Sm⁺掺杂到具有层状结构的10,12-二十五碳二炔酸(PCDA)纳米粒子中,得到二炔酸/稀土离子(PCDA-RE)纳米复合物．随后在稍微高于二炔酸熔点的温度下对PCDA-RE纳米复合物进行退火处理,退火后的PCDA-RE纳米复合物发生拓扑聚合反应得到聚二炔酸/稀土离子(PDA-RE)纳米复合物．虽然纯聚二炔酸的热致变色过程是不可逆的,但是PDA-Sm纳米复合物和PDA-Dy纳米复合物分别具有不完全和完全热致可逆变色的性能．研究表明,PDA-RE纳米复合     

Magnetization and heat capacity studies of double perovskite compounds Ba2SmRuO6 and Ba2DyRuO6

Here we report the magnetic and heat capacity studies of the double perovskite compounds Ba₂SmRuO₆ and Ba₂DyRuO₆. Antiferromagnetic transitions are inferred at 54 and 47 K in Ba₂SmRuO₆ and Ba₂DyRuO₆, respectively, in the magnetization measurements. Heat capacity measurements show large jumps at the corresponding temperatures and confirm the bulk magnetic ordering. Both the measurements provide clear indication of the ordering of the rare earth moments also along with the Ruthenium moments. However, the heat capacity results suggest that the ordering of rare earth magnetic moments is spread over a large temperature range. An anomaly observed in the magnetization measurements at 42 K (below the magnetic ordering) in Ba₂SmRuO₆ is discerned as a reorientation of Sm³⁺ moments.     

Anomalous properties of thin films of ferromagnetic superconductors

Anomalous magnetic and superconducting behavior which originates from the electromagnetic interaction between the persistent current and the rare earth magnetic moments is theoretically predicted in thin films of ferromagnetic superconductors. It is shown that the ferromagnetic ordering can coexist with superconductivity for films of thickness smaller than the London penetration depth. The ferromagnetic phase transition is of the second order and its critical temperature depends on the thickness of the film.     

Thermionic emission properties of LaB6 and CeB6 in connection with their surface states,examination by XPS,Auger spectroscopy and the Kelvin method

The surface of the thermionic emitters LaB₆ and CeB₆ was investigated as a function of temperature by means of XPS, Auger electron spectrosopy and the Kelvin method. The hexaborides are sensitive to oxidation at room temperature, a thin layer of rare earth oxide and boron oxide having been detected at their surfaces. This study has shown the influence of surface carbon on the Auger line intensities of lanthanum and boron in the case of LaB₆. A surface cleaning by ionic bombardment leads to a preferential erosion of the rare earth with respect to boron. One may conclude that the emission mechanism in hexaborides is an intrinsic property of the material. The hypothesis previously proposed by other authors, that the low work function may be due to the presence of a layer of rare earth metal on the LaB₆ substrate was not confirmed.     

稀土La(Ⅲ)、Nd(Ⅲ)与牛血清白蛋白的相互作用

采用紫外吸收、荧光光谱和红外光谱,研究了稀土离子La(Ⅲ)和Nd(Ⅲ)与牛血清白蛋白(BSA)的相互作用.结果表明:La(Ⅲ)和Nd(Ⅲ)离子能配位诱导BSA,使其分子中色氨酸和酪氨酸芳杂环疏水基团外露,在280 nm处的吸收增强而表现出增色效应和较小的蓝移.La(Ⅲ)和Nd(Ⅲ)可以有规律地猝灭BSA的内源荧光,其猝...     

Rare earth elements as activators of zinc sulfide cathodoluminophors

Luminescence spectra of zinc sulfide luminophore activated by ten rare earth elements and their relative yield of cathodoluminescence in the visible region are studied at room temperature. The effect of the conditions of synthesis is studied. Using ZnS · CdS-Ho phosphor as an example, the marked effect of a change in lattice constant and the width of the forbidden zone on luminescence of rare earth centers is shown.     

Impurity effect on the Raman spectra of Sr0.6Ba0.4Nb2O6

Impurity effect on the rare earth ion doped Sr_0.6Ba_0.4Nb₂O₆(SBN40) was studied at room temperature. Doping the rare earth ions of Pr³⁺ or Nd³⁺ changed the Raman profile: spectral broadening, central frequency shifts and relative intensity decreasing. Two reasons are considered according to the ferroelectric and optical properties of the rare earth ion doped SBN40: impurity-induced crystal disorder and the crystal structure change. SBN40 is the general disorder crystal and the disorder which is enhanced by doping the rare earth ion is especially strong along the x?y plane of the material compared with that along the polar C-axis.     

Measurement of the effective atomic number of some transition and rare earth compounds using the Rayleigh to Compton scattering ratio of gamma radiation

The effective atomic numbers of some transition and rare earth compounds have been determined by measuring the ratio of Rayleigh to Compton scattering signal using 59.5?keV gamma radiation from americium-241 radioactive source. The scattered gamma photons from the elements and compounds at an angle of 90° were detected using an ORTEC high-purity germanium detector coupled with 16K multi-channel analyzer. By measuring the ratio of Rayleigh to Compton scattered signal (momentum transfer 3.38?Å^?1), the effective atomic numbers of the transition and rare earth compounds have been determined and compared with theoretical values predicted by AutoZeff, power law, and direct method.     

ICP-MS测定中草药狼毒中稀土和微量元素

研究了电感耦合等离子体质谱法(ICP-MS)测定中草药狼毒中稀土和微量元素的方法,样品处理通过低温灰化方法与硝酸-过氧化氢消解方法比较,实验确认微量元素采用低温灰化法制备样品, 稀土元素采用酸消化法制备样品,可以满足该方法检测要求,具有测试方法准确、快速等优点。 方法的准确度在1.21%～15.15%, 精密度在0.38%～8.54%之间。 该方法完全可以满足中草药样品中稀土和微量元素检测要求。     

Invar properties in the rare earth-3d transition metal alloys

The RCo₂ and R₂Fe₁₇ compounds (R = rare earth) exhibit Invar-like thermal expansion anomalies below their ordering temperatures. These spontaneous volume magnetostrictions are discussed by considering their magnetic properties. In RCo₂ compounds there is no intrisinc Co-moment is induced by the exchange and applied fields. The volume expansion anomaly is associated with the onset of the 3d magnetic moment. IN R₂Fe₁₇ compounds there is an intrisinc Fe- moment. Magnetic structures give evidence for positive and negative exchange interactions between Fe atoms which are strongly distance dependent. The thermal expansion anomaly is a result of this distance of the magnetic interactions.     

Raman spectra of soda-lime-silicate glass doped with rare earth

Soda-lime-silicate glasses doped with different rare earth oxides (La₂O₃, CeO₂, Nd₂O₃, Gd₂O₃ and Y₂O₃) of 1 mol% content were prepared by the traditional melting-quenching methods. In order to reveal the effects of rare earth elements on the behavior of soda-lime-silicate glass the structures of soda-lime-silicate glasses doped with different rare earth oxides were determined using an INVIA confocal microRaman spectrometer equipped with a CCD detector, and viscosities of glass melts were measured using a rotating crucible viscometer; the melting temperature of the studied glasses was derived on the basis of the Arrhenius equation. Three expressions of the fraction of non-bridging oxygen (NBO/NBO+BO), average number of non-bridging oxygen (NBO) per tetrahedron (NBO/tetrahedron) and average number of bridging corners per tetrahedron (bridges/tetrahedron) for investigated soda-lime-silicate glasses were given, and the effect of rare earth dopants on the structure of soda-lime-silicate was characterized by the Raman shift, variation of the [SiO₄] tetrahedron structural unit Qⁿ (n=1,2,3,4), fraction of non-bridging oxygen and the average number of bridging corners per tetrahedron. The effect of doping rare earth oxides into glass on the viscosity and melting temperature was interpreted by changes in structure of soda-lime-silicate glasses doped with rare earth oxides.     

ZnO:Er3+纳米晶的制备和室温发射

文章采用化学沉淀法制备纳米晶ZnO：Er^3＋粉体,所制备的纳米晶ZnO：Er^3＋粉体具有稀土离子特征强室温可见发射和近红外发射现象,且首次观测到纳米晶ZnO基质和稀土Er离子之间有有效的能晕传递。     

Vibrational modes of rare‐earth formates

In this work we investigate the room‐temperature Raman spectra of several rare‐earth [RE(HCOO)₃; RE = La, Pr, Nd, Gd, Tb and Y] formates. Polarized measurements were carried out for La(HCOO)₃ yielding the observation of most of the Raman‐active phonons predicted by group theory analysis. The respective assignment is given based on the formate vibrations and correlations with previous results in other RE(HCOO)₃ systems. The wavenumber ‘softening’ observed when RE goes from Y to La is accounted for the lattice expansion. Copyright © 2009 John Wiley & Sons, Ltd.     

Combined Study of Structural,Magnetic and Transport Properties of Eu_(0.5)Ln_(0.5)BiS_2F Superconductor

Superconductivity below 0.3 K and a charge-density-wave-like(CDW-like) anomaly at 280 K were observed in EuBiS_2F recently.Here we report a systematic study of structural and transport properties in Eu_(0.5)Ln_(0.5)BiS_2F(Ln=La,Ce,Pr,Nd,Sm) by electrical resistivity,magnetization,and specific heat measurements.The lattice constants have a significant change upon rare earth substitution for Eu,suggesting an effective doping.As Ln is changed from Sm to La,the superconducting transition temperature T_c increases from 1.55 K to 2.8 K.In contrast to the metallic parent compound,the temperature dependence of electrical resistivity displays semiconductinglike behavior for all the Eu_(0.5)Ln_(0.5)BiS_2F samples.Meanwhile,the CDW-like anomaly observed in EuBiS2F is completely suppressed.Unlike the mixed valence state in the undoped compound,Eu ions in these rareearth-doped samples are mainly divalent.A specific anomaly at 1.3 K resembling that in EuBiS2F suggests the coexistence of superconductivity and spin glass state for Eu_(0.5)La_(0.5)BiS_2F.Coexistence of ferromagnetic order and superconductivity is found below 2.2 K in Eu_(0.5)Ce_(0.5)BiS_2F samples.Our results supplies a rich diagram showing that many interesting properties can be induced in BiS_2-based compounds.     

Rare earth paramagnetism,as studied by μSR

Some recent result of muon spin relaxation measurements in rare earth metals and intermetallic compounds are reviewed. Special emphasis is put on measurements that relate to the properties of correlated regions of spins existing relatively far above the ordering temperature in the rare earth ions. As far as comparable data from paramagnetic neutron scattering exist, they will be discussed in the same framework. For each temperature the correlated regions (or short-lived magnetic clusters) are characterized by their size, possible anisotropy with respect to the crystalline axes and their lifetime. The actual form of the interaction between the rare earth spins themselves and with the crystal fields determine the temperature dependence of these properties; a strong dipole interaction can, for instance, be expected to change the critical behaviour nearT _c . Much of the time will be devoted to experiments on Gd-metal where there are experimental indications that several interesting phenomena occur: (1) a strong effect of a cross-over from a non-conserved dynamics (dipolar) regime to a conserved (exchange dominated) regime some 10 K aboveT _c , (2) an anisotropy of the magnetic clusters with respect to the hexagonalc-axis, and (3), a persistence of spin correlations far aboveT _c . Some attempts to correlate the rare earth spin relaxation times measured in this region with cluster lifetimes deduced from neutron scattering will be reviewed, as well as a model for understanding these lifetimes in terms of temperature dependent cluster wall motion, which is determined by exchange and magnetic anisotropy parameters. Effects of possible quantum correlations originating from the “spin system+bath” interaction will be mentioned.