十种稀土金属电阻的压力效应

 使用Bundy和Dunn发展起来的带有烧结金刚石砧的Drickamer型高压装置，用固定点测压法标定实验压力，在室温及0~43 GPa的压力范围内测量了稀土金属中Pr、Nd、Sm、Gd、Tb、Dy、Ho、Tm、Lu和Yb的电阻随压力的变化。在各稀土元素的电阻随压力变化的曲线上，观测到了若干“凸起”和斜率突变点，根据Jayaraman提出的三价稀土在压力作用下的相变顺序，得到了这些突（凸）变点分别对应着hcp→Sm-type→dhcp→fcc相变顺序中的某一类型的相变压力。此外还观测到了Pr、Gd、Tb的fcc相随着压力再增高而发生的相变，根据已报导的关于Pr的工作，推测Gd和Tb的这一相变应为fcc→dfcc相变，它们分别发生在22.0和24.5 GPa。在本工作所得结果基础上对Johansson的三价稀土总相图进行了修正。     

Interplay of iron and rare-earth magnetic order in rare-earth iron pnictide superconductors under magnetic field

The magnetic properties of iron pnictide superconductors with magnetic rare-earth ions under strong magnetic field are investigated based on the cluster self-consistent field method. Starting from an effective Heisenberg model, we present the evolution of magnetic structures on magnetic field in RFeAsO(R = Ce, Pr, Nd, Sm, Gd, and Tb) and RFe_2As_2(R =Eu) compounds. It is found that spin-flop transition occurs in both rare-earth and iron layers under magnetic field, in good agreement with the experimental results. The interplay between rare-earth and iron spins plays a key role in the magneticfield-driven magnetic phase transition, which suggests that the rare-earth layers can modulate the magnetic behaviors of iron layers. In addition, the factors that affect the critical magnetic field for spin-flop transition are also discussed.     

Spin and temperature dependence of the magnetic hyperfine field of Cd in the rare earth-aluminum Lavesphase compounds RAl2

Perturbed angular correlation spectroscopy has been used to investigate the combined magnetic and electric hyperfine interaction of the probe nucleus ¹¹¹Cd in ferromagnetically ordered rare earth (R)-dialuminides RAl₂ as a function of temperature for the rare earth constituents R=Pr, Nd, Sm, Eu, Tb, Dy, Ho and Er. In compounds with two magnetically non-equivalent Al sites (R=Sm, Tb, Ho, Er), the magnetic hyperfine field was found to be strongly anisotropic. This anisotropy is much greater than the anisotropic dipolar fields, suggesting a contribution of the anisotropic 4f-electron density to magnetic hyperfine field at the closed-shell probe nucleus. The spin dependence of the magnetic hyperfine field reflects a decrease of the effective exchange parameter of the indirect coupling with increasing R atomic number. For the compounds with the R constituents R=Pr, Nd, Tb, Dy and Ho the parameters B₄, B₆ of the interaction of the crystal field interaction have been determined from the temperature dependence of the magnetic hyperfine field. The ¹¹¹Cd PAC spectrum of EuAl₂ at 9 K confirms the antiferromagnetic structure of this compound.     

Magnetoelastic properties of RCo2 films

Magnetic and magnetoelastic properties of films of the compounds RCo₂ (R-Nd, Pr, Sm, Gd, Tb, Dy, Y) have been investigated. It is shown that the preparation technology, crystal structure of the alloys, atomic number of the rare-earth elements have a large effect on the behavior of the parameters considered.     

Magnetocaloric effect and magnetic phase transitions in nanocrystalline rare-earth metals: Tb, Dy, and Gd

The magnetocaloric effect of rare-earth metals (REMs) Gd, Tb, and Dy in the nanostructured state is investigated. The ranges of working temperatures and cool capacity for materials based on nanocrystalline REMs are calculated from the experimental data. These results enable us to evaluate in detail the magnetic properties of REMs in a nanocrystalline state. It is shown that nanocrystalline Dy possesses the largest cool capacity, making this material most effective for magnetic cooling in the temperature range of 82–134 K.     

The effects of light and heavy rare-earth elements on magnetic ordering in Sm

The effect of 5% of Pr, Nd, Gd and Tb on the magnetic ordering temperatures of Sm has been examined by susceptibility and resistivity measurements. Neither transition correlates with the average de Gennes factor. The data for the as cast Gd and Tb alloys reveal the presence of the dhcp structure.     

Magnetic and superconducting properties of Tl(Sr1.5R0.5)CaCu2O7−δ compounds

DC magnetic susceptibility and resistivity measurements have been performed on 14 Tl(Sr_1.5R_0.5)CaCu₂O_7−δ compounds with R=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. All samples except the Ce-doped compound show superconducting phase transition temperature around 80–90 K. The rare-earth atoms behave as local moments above the superconducting transition temperature of these compounds. Mechanism of filling of holes in the CuO₂ plane can be employed to interpret the suppression or enhancement of superconductivity by rare-earth ions in Tl(Sr_1.5R_0.5)CaCu₂O_7−δ.     

Spectroscopic Study on the Photophysical Properties of Lanthanide Complexes with 2, 2′-Bipyridine-N, N′-dioxide

Five novel lanthanide (Eu3+, Tb3+, Gd3+, Sm3+ and Dy3+) complexes with 2, 2'-bipyridine-N, N'-dioxide (bipyO2) were synthesized and characterized by elemental analysis, IR spectrum. The triplet state energy of bipy O2 was determined to be 22275 cm(-1) with the phosphorescence spectrum of bipy O2 and its gadolinium complex. The photophysical properties of these complexes indicated that the triplet state energy of the ligand is suitable for the sensitization of the luminescence of Eu3+, Tb3+, Sm3+ and Dy3+, especially of Tb3+.     

Thermoluminescence of rare earth activated CdSO4, SrSO4 and BaSO4

The thermoluminescence (TL) of rare earth (RE) activated sulfates of Cd, Sr and Ba was studied above room temperature. Many of the phosphors prepared exhibit an extremely bright TL following X-irradiation (most notably with Sm, Eu, Tb, Dy and Tm dopants), having an efficiency comparable to that of the highest sensitivity phosphors available for TL dosimetry, and exhibiting activator-induced glow peaks between 405 and 480°K. In a given lattice, the RE³⁺ ions produce a characteristic glow peak at the same temperature (independent of the particular RE ion), whereas Eu²⁺ produces a single glow peak at a different temperature. A decrease in glow peak temperature with increasing interatomic spacing was observed in the homologous SrSO₄-BaSO₄ system - this shift being most pronounced in the Eu²⁺ -doped materials. TL emission spectra were obtained for trivalent Sm, Tb, Dy and Tm and for divalent Eu in these sulfates (and also in CaSO₄).     

Magneto-optical Faraday and Kerr effect of orthoferrite thin films at high temperatures

Orthoferrites present, as bulk materials, reorientation transitions of their magnetic moment alignment at temperatures depending on the rare-earth (RE) ion. In particular, orthoferrites (REFeO₃) with RE = Sm, Dy, present this transition at T _SRT = 443 K and 36 K, respectively. The spectra of the complex Kerr and Faraday angle have been measured on orthoferrite thin films (RE = Sm, Dy, Y), which were prepared by pulsed laser deposition on amorphous quartz substrates. The obtained spectra exhibit contributions of both surfaces and interfaces. Propagation effects of the polarized light in the magneto-optical medium which is interpreted in terms of a simplified theoretical formalism, is also observed. For selected photon energies, temperature dependent Faraday rotation measurements, , on orthoferrite thin films (RE = Sm, Dy, Y) have been performed. A quite different thermal variation compared to the bulk magnetization has been observed. Curie temperatures are found to be close to the bulk values or slightly larger by 10 K to 20 K as in the case of DyFeO₃ and YFeO₃. For RE = Sm and Dy, increases with increasing temperature contrary to the saturation magnetization, passes through a maximum at about 460 K and vanishes with a T _C of 647±18 K, 695 K for RE = Sm and Dy respectively. Received 28 July 2000     

稀土配合物的荧光特性实验研究

对稀土元素铕、铽、镝的氯化物与咪唑二元配合物,与丙氨酸、咪唑三元配合物,乙酰甘氨酸铕、镧、钕、铕与苯并咪唑配合物以及它们的配体,以可见光为激发光进行了荧光光谱测量,比较了不同稀土元素的荧光特性,分析了不同配体对稀土离子荧光特性的影响,讨论了稀土离子在配合物中的发光机制,同时还观察分析了升频荧光现象.     

Magnetic anisotropy in Fe/rare‐earth multilayers

Magnetic anisotropy of Fe/RE multilayers (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) was studied using ⁵⁷Fe Mössbauer spectroscopy. Perpendicular magnetic anisotropy was observed in Fe/Pr, Fe/Nd, Fe/Tb, and Fe/Dy multilayers. The external field dependence of the direction of magnetic moments was also examined for Fe/Tb multilayers. The results imply that the perpendicular magnetic anisotropy originates from the single ionic anisotropy of RE at the interfaces.     

稀土乙酰丙酮苯并咪唑三元配合物合成和荧光性质研究

用稀土氯化物与乙酰丙酮及苯并咪唑在 95 %乙醇溶液中反应 ,合成了 6个稀土 (L a3 +、Sm3 +、Eu3 +、Tb3 + 、Dy3 + 、Y3 + )乙酰丙酮苯并咪唑三元配合物。用红外光谱和紫外光谱表征了配合物并对其荧光性质进行了研究。结果表明 ,Sm、Eu、Tb和 Dy的配合物能发出中心离子的特征荧光 ,发光强度顺序为 Tb>Dy>Sm>Eu     

苯甲酰三氟乙酰丙酮与铕、铽、钐、镝配合物合成和荧光光谱研究

本文合成了苯甲酰三氟乙酰丙酮(简称L)和三苯基氧化膦(TPPO)、联吡啶(Bipy)、邻菲罗林(Phen).四甲基氢氧化铵(NMe4OH)与Eu、Tb、Sm、Dy的三合型和四合型共十六种配合物,常温下研究了它们的固体粉末荧光光谱,发现四种铕配合物中Eu3+的5D0—7F2跃迁最强,而且EuL3Bipy和EuL3(TPPO)2发光相对强度特别高,其余三种离子的特征跃迁能级:Tb3+是3D4—7F5,Sm3+是4G5/2—6H3/2,Dy3+是4F9/2—6H1/2,除TbL3(TPPO)2外,其余发光强度不大.发现四合型NMe4EuL4在非极性溶剂中荧光强度最大,表明其稳定性高.在PS树脂中添加微量EuL3Bipy或EuL3(TPPO)2,在～365nm光照射下显示鲜艳的红色荧光.     

磁感应强度和冷却速率对Tb_(0.27)Dy_(0.73)Fe_(1.95)合金凝固过程中取向行为的影响

实验研究了磁感应强度和冷却速率对Tb_(0.27)Dy_(0.73)Fe_(1.95)合金凝固过程中(Tb,Dy)Fe_2相取向行为及合金磁性能的影响.结果表明,将强磁场作用于Tb_(0.27)Dy_(0.73)Fe_(1.95)合金的凝固过程可以制备出(Tb,Dy)Fe_2相沿111取向的组织,同时显著提高了合金的磁致伸缩性能;通过提高磁感应强度可以在更快的冷却速率下得到111取向的组织;在4-10 T范围内,随着冷却速率的增加,(Tb,Dy)Fe_2相沿111取向所需的磁感应强度增加,而发生(110)取向的磁感应强度减小.随着冷却速率的增加,合金的饱和磁化强度增加,而强磁场的施加对合金饱和磁化强度的变化没有明显影响.(Tb,Dy)Fe_2相的取向行为受*Tb,Dy)Fe_3相取向行为的影响,且由磁晶各向异性能与磁场作用时间共同控制.     

双酰胺稀土配合物的合成及荧光性能

为寻求发光性能良好的配合物,设计合成了一种新的双酰胺配体1,4-二 苯(L),并在氯仿和乙酸乙酯溶液中合成了其与硝酸钐、硝酸铕和硝酸铽的发光稀土配合物。元素分析数据表明稀土硝酸盐与配体形成的是 1 : 1 型的配合物;红外光谱显示配合物具有相似的配位结构。对配体及其配合物的荧光进行了详细的研究,结果表明:钐、铕和铽配合物分别呈现出Sm³⁺、Eu³⁺、Tb³⁺的特征发射,铕离子处于不对称中心格位,硝酸铽配合物荧光相对强度最大。     

硼酸盐玻璃中某些稀土离子的浓度效应及其能量传递过程

本文系统地报道了硼酸盐玻璃中Ce3+、Sm33+、Eu3+、Ga3+、Tb3+、Dy3+浓度效应,观察到Eu3+、Gd3+、Tb3+在硼酸盐玻璃中随浓度增加其发光强度增强,而Ce3+、Sm3+、Dy3+当其浓度增加到一定数值后,发光强度反而减弱,初步探讨了不同浓度效应的原因.本文还观察到硼玻璃中某些稀土离子对Eu3+、Tb3+离子发光的敏化作用,及讨论了Gd3+和Eu3+、Tb3+之间的能量传递过程,计算其能量传递的效率和几率.估计了能量传递的规律机理.     

Novel structural phases of Dy thin films on W(1 1 2)

Thin films of the rare-earth metal Dy were grown on W(1 1 2) at room temperature and 570 K. Then the resultant film morphologies were characterised by LEED and STM. A series of novel film morphologies, including c(4 × 6), c(5 × 12) and (5 × 8) structures, were found that are unique among the rare-earth metals. High thermal stability was found for the Dy films (up to 1650 K, close to the melting point at 1685 K) such that the Dy atoms preserved an ordered structure and the Dy volatility was less than would be expected from its vapour pressure. This is an indication of strong electronic interactions between the Dy atoms and the W(1 1 2) substrate.     

稀土配合物RE(TPTZ)Cl_3的合成、表征及荧光性能研究

首次以2,4,6-三吡啶基三嗪（TPTZ）与Sm, Eu, Tb和Dy氯化物反应,合成四种单一稀土配合物以及Tb分别1∶1掺Gd, Y, La的三种异核配合物。经元素分析、稀土络合滴定、摩尔电导率、红外光谱、紫外光谱和差热-热重测定表明,配合物的组成分别为RE（TPTZ）Cl3·3H2O（RE=Sm, Eu, Tb, Dy）和Tb0.5Ln0.5（TPTZ）Cl3·3H2O（Ln=Gd, Y, La）;TPTZ作为三齿配体与稀土离子配位,即中心环提供一个N原子,两个吡啶环分别提供一个N原子;配合物中3个水分子与稀土离子配位,1个Cl-在外界,2个在内界,为1∶1型电解质;配合物内外界可能为[RE（TPTZ）（H2O）3Cl2] Cl,稀土离子的配位数为8。配合物的荧光光谱测试表明,四种单一稀土配合物中,Tb配合物发光最强;三种1∶1掺杂异核Tb配合物荧光强度大于纯Tb配合物,表明Y3＋, La3＋和Gd3＋都可以敏化Tb3＋的发光,其中Gd3＋的敏化作用最强,Y3＋次之,La3＋最差。     

Magnetocaloric effect in R2Fe17 (R=Sm,Gd, Tb,Dy, Er)

A series of R₂Fe₁₇ (R=Sm, Gd, Tb, Dy, Er) have been synthesized. The magnetocaloric effect (MCE) of these compounds has been investigated by means of magnetic measurements in the vicinity of their Curie temperature. The Curie temperature of Er₂Fe₁₇ is 294 K. The maximum magnetic entropy change of Er₂Fe₁₇ under 5 T magnetic field is ∼3.68 J/kg K. In the R₂Fe₁₇ (R=Sm, Gd, Tb, Dy, Er) system, the maximum magnetic entropy change under 1.5 T magnetic field is 1.72, 0.89, 1.32, 1.59, 1.68 J/kg K corresponding to their Curie temperature (400, 472, 415, 364, 294 K), respectively.