Tb Tm Research Articles

Effects of rare earth doping on the superconducting properties of MgB2

Doping effects of rare earth oxides (REOy: RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) on the superconducting properties of MgB2 were investigated. Large fraction of the added RE turned into impurity phases: REB6 for RE=La–Gd and Yb, and REB4 for RE=Tb–Tm and Lu. We observed an increase in c-axis length from 3.523 to 3.533Å when doped with Lu. Clear decreases in transition temperatures were observed in samples doped with Sm, Eu, Gd, Tm, Yb and Lu, indicating that these elements were successfully substituted for Mg. The decreases in Tc were most drastic in Yb-doped samples (Tc∼32K).

Magnetic and transport properties of R(Mn, In) 2 (R—rare-earth metals) with AlB 2-structure type

We studied the crystal structure and magnetic properties of ternary rare-earth R(Mn,In) 2 compounds (R=Y, La, Ce, Tb–Tm, Lu), which crystallize in the AlB 2-structure type with approximate stoichiometry RMn 0.67In 1.33, but adopting a variable Mn deficiency. YMn 0.92In 1.08 orders antiferromagnetically below T N ≈ 247 K, CeMn 0.65In 1.35 is ferromagnetic with T C=134 K. The compounds with magnetic rare earths tend to a glassy magnetic state, presumably due to the disorder in the Mn/In sublattice together with competing exchange interactions. The disorder has also a dramatic impact on the temperature dependence of the electrical resistivity, which is rather flat due to a strong scattering. The absence of long-range order was proved also by specific-heat measurements. Hydrogen absorption, tested for several compounds, led to the synthesis of LaMn 0.49In 1.51H 0.75(5).

Avantages et limites des tests sanguins in vitro lymphocytes T/interféron gamma comparativement au test intradermique à la tuberculine pour le diagnostic de tuberculose ☆

The development of in vitro blood tests that measure the delayed hypersensitivity reaction developed after contact with Mycobacterium tuberculosis will change progressively the diagnosis of M. tuberculosis infection. These blood assays (Quantiferon TB Gold TM, Cellestis, Australia; T-SPOT.TB TM, Oxford Immunotec, United Kingdom) use specific, complex M. tuberculosis antigens (ESAT-6 and CFP-10), whereas the intra-dermal Mantoux test is done with tuberculin, a complex mixture of more than 200 antigens. ESAT-6 and CFP-10 are absent from all the BCG vaccine strains used throughout the world. Significant improvement in the specificity with equivalent or increased sensitivity of the in vitro tests compared to the Mantoux test will lead eventually to replacement of the latter.

Effect of fluxes containing oxides on tungsten inert gas welding process

The use of an inorganic powder, termed activating flux, is a technique that can be used to improve the tungsten inert gas welding process. The activated tunsten inert gas (ATIG) process greatly increases single pass depth penetration. In the present work the activating effect of different oxides on 304L stainless steel was studied, to determine the main relationships between the oxide propertie(s) and the weld bead geometry variation and consequently to determine the mechanism(s) occurring during the ATIG welding process. The results show that oxide melting point Tm, the liquid state (Tb–Tm), the lattice energy EL, and the quantity of oxygen that can be liberated seem to play an important role, even though Tm is the main property. Moreover, for some oxides, the hygrometry rate is another property that can increase the activating effect.

Er36Pt102−xSi32(x= 2.6), a new structure type of a ternary intermetallic silicide

The title erbium platinum silicide compound represents a new structure type of intermetallic silicide with platinum and a heavy rare earth element (Tb–Tm). Four atoms exhibit disorder. Coordination polyhedra of most of the Pt atoms are distorted cuboctahedra; coordination polyhedra of the silicon atoms are distorted trigonal prisms with three additional atoms capping the square faces.

Thermal properties of rare earth dodecaborides

We have measured heat capacity and thermal expansion of rare earth dodecaborides REB 12 ( RE=Y, Tb–Tm, Lu). YB 12 and LuB 12 are diamagnetics whereas the other dodecaborides are ordered antiferromagnetically. The amplitude of the heat capacity discontinuity at the Néel temperature and the shape of the heat capacity variation in the critical region for all these antiferromagnetics are characteristics for amplitude-modulated magnetic structures. In the ordered state TbB 12 reveals two first-order phase transitions, most likely due to magnetic structure changes. The heat capacity of ErB 12 just below the Néel point shows an anomaly of unclear origin. From the Schottky contribution to the heat capacity we have determined crystal field parameters. They are completely different than that is estimated from Point Charge Model.

A neutron diffraction study of HfFe6Ge6-type ScMn6Ge6−xGax compounds and YMn6Ge6−xGax compounds (0.3≤x≤1.6)

The HfFe6Ge6-type ScMn6Ge6−xGax and YMn6Ge6−xGax solid solution (0.3≤x≤1.6) have been studied by magnetization measurements, microprobe analysis and powder neutron diffraction. The ScMn6Ge5.63Ga0.37 and YMn6Ge5.66Ga0.34 compounds display skewed helimagnetic structures in the whole 2–300 K studied range. The YMn6Ge5.35Ga0.65 compound displays a helimagnetic structure above 160 K and a ferromagnetic structure below 40 K. In the intermediate temperature range, both structures coexist. Finally, the ScMn6Ge5.34Ga0.66, ScMn6Ge5.12Ga0.88 and YMn6Ge5.08Ga0.92 display ferromagnetic structure in the whole 2–300 K range. The results are discussed and compared with those of all the RMn6Ge6−xGax compounds (R=Tb–Tm, Lu; 0≤x≤1.0) studied by neutron diffraction.

A neutron diffraction study of HfFe6Ge6-type DyMn6Ge6−xGax compounds (x=0.1, 0.2 and 1.0)

DyMn6Ge6−xGax compounds (x=0.1, 0.2 and 1.0) were studied by magnetization measurements and powder neutron diffraction. DyMn6Ge5.9Ga0.1 and DyMn6Ge5.8Ga0.2 display helical structures between TN=427 and 422 K, respectively, and between Tt=110 and 147 K, respectively. Below Tt, conical structures with the cone axis close to the c-axis and semi-cone angles of about 50 and 45°, respectively, were measured. The moment values measured at 2 K were μMn=2.27(10) and 2.26(6) μB, respectively, and μDy=9.90(20) and 9.73(16) μB, respectively. DyMn6Ge5Ga is ferrimagnetic below Tc=392 K. At 2 K, the moment values are μMn=2.22(10) and μDy=9.90(17) μB. The angle between the moment direction and the c-axis is θ=46(2)°. This value increases with temperature to θ=64(4)° at 300 K. The results are discussed and compared with previous neutron diffraction studies on isotypic RMn6Ge6 and RMn6Ge6−xGax compounds (R=Tb–Tm).

Effect of the crystalline electric field on the Néel temperatures of RCu 2 compounds

Values for the Néel temperature of the RCu 2 compounds (R=Tb–Tm) have been calculated using a molecular-field model including crystalline-electric-field effect as presented by Noakes and Shenoy. The calculated results show that the unusual behavior, at the Néel temperatures, of these compounds can be explained on the basis of this model.

Structural, Electronic, and Magnetic Properties of Ternary Rare-Earth Metal Borocarbides R5B2C5 (R=Y, Ce–Tm) Containing BC2 “Molecules”

The borocarbides R5B2C5 (R=Y, Ce–Tm) were prepared by arc melting from the pure rare-earth metals, boron and carbon. The structural arrangement of these compounds, which crystallize in the tetragonal space group P4/ncc, consists of a three-dimensional framework of rare-earth atoms resulting from the stacking of slightly corrugated two-dimensional squares, which lead to the formation of octahedral holes and distorted bicapped square antiprismatic cavities filled with isolated carbon atoms and C–B–C chains, respectively. In contrast to the heavy rare-earth metal (Gd–Tm)-containing compounds which melt congruently, those with the early rare-earth elements (Ce–Sm) are formed peritectically. The electronic structure and chemical bonding of Sm5B2C5 and Gd5B2C5 are analyzed using extended Hückel tight-binding and density-functional theory calculations. Results reveal a rather strong covalency between the metallic matrix and the BC2 groups and the isolated carbon atoms, respectively, similar to what is generally computed in related rare-earth metal borocarbides. Magnetic susceptibility measurements indicate that all samples, which were investigated, undergo ferromagnetic transitions in the temperature region below T=130 K. The heavy rare-earth metal (Tb–Tm) borocarbides exhibit a magnetic behavior typical of narrow-domain-wall ferromagnets. Both the Curie temperatures, TC, as well as the paramagnetic Curie temperatures, ΘP, scale approximately with the de Gennes factor. Hence the indirect exchange interaction via conduction electrons (RKKY-interacting) is the dominating force of the R–R coupling mechanism.

Crystallographic data of new ternary Co 2Si-type RTSi (R=Y, Tb–Tm, T=Mn, Ru) compounds

Investigations made by powder X-ray diffraction on new ternary RMnSi compounds (R=Tb–Er) and RRuSi (R=Y, Tb–Tm) are reported. They crystallize in the well-known orthorhombic Co 2Si-type structure (space group Pnma).

New ternary compounds R 2Mn 3Si 5 (R=Tb–Er) with Sc 2Fe 3Si 5-type structure

Investigations made by powder X-ray diffraction on new ternary R 2Mn 3Si 5 compounds (R=Tb–Tm) are reported. Tb 2Mn 3Si 5 ( a=10.626(1) Å, c=5.4570(6) Å), Dy 2Mn 3Si 5 ( a=10.595(1) Å, c=5.4320(6) Å), Ho 2Mn 3Si 5 ( a=10.584(1) Å, c=5.4169(6) Å) and Er 2Mn 3Si 5 ( a=10.568(1) Å, c=5.4027(5) Å) crystallize in the tetragonal Sc 2Fe 3Si 5-type structure (space group P4/mnc).

Magnetic properties of RPdSn and RPdSb compounds

The magnetic properties of the ternary RPdSn (R ≡ CeNd, TbTm) and RPdSb (R ≡ CeNd, Sm, GdHo) compounds are determined. For the majority of these compounds at low temperatures a magnetic ordering of the rare earth moments is observed. The values of the ordering temperatures (TN or TC) are determined. The TC and TN values do not follow the de Gennes scaling for either group of compounds.

Thermodynamic quantities associated with the interaction of mixed ligand rare earth chelates of EDTA with TPP and ATP

Potentiometric equilibrium measurements have been made at 2, 25, 35 and 45° for the combination of protonated (tetranegative) and fully dissociated pentanegative) anions of TPP and of the tetranegative anions of ATP with 13 rare earth ions in a 1:1:1 ratio of rare earth: EDTA:TPP and rare earth: EDTA: ATP. The enthalpy and entropy changes for the formation of protonated and normal chelates of TPP and for the normal chelates of ATP are calculated from temperature coefficient data. The partial molal entropies ( S ̄ LnXY ) and entropy of complexation in the gas phase (Δ S g LN XY) of the mixed ligand rare earth complexes of EDTA with ATP and TPP fall into three groups LaPr, PrTb and TbTm indicating a change in the hydration number of the lanthanide ions in three respective groups. The enthalpies for the mixed ligand rare earth complex formation (Δ H°) change in an erratic manner both for the ATP and TPP mixed ligand complexes.

Magnetic Properties of Rare-Earth Metals and Alloys

A review of neutron diffraction studies of the magnetic properties of rare-earth metals and alloys is presented. For each of the pure metals Tb, Dy, Ho, Er, and Tm there is observed a transition at a temperature TN to an oscillatory antiferromagnetic configuration (helical or linear oscillator type). At lower temperatures, further transitions to ferromagnetic, ferromagnetic spiral, or antiphase domain-type configurations are observed. For Gd, only the ferromagnetic configuration is found. The magnetic moments in the ordered configurations at low temperatures approach the values expected from the corresponding free tripositive ions. In the first half of the series only Nd has been studied by single-crystal methods, but Ce, Pr, and Eu have now been investigated with polycrystalline samples. The data for Ce are complicated by the existence of several allotropic forms, but a complex antiferromagnetic structure appears to be associated with the hexagonal form at low temperatures. For Nd and Pr, oscillatory antiferromagnetic configurations are observed at very low temperatures in which, as in Ce, the moments have magnitudes considerably smaller than the free-ion values, which result suggests a strong influence due to the crystalline field. A helical spin structure in bcc Eu has been reported in which the moment of Eu is somewhat smaller than that of Eu++. A number of alloy systems, R-Y, R-R′, and R-La, where R and R′ are among the group Tb–Tm, have been investigated and results are discussed. These results and those for the pure metals are discussed relative to the theory of the magnetism of the rare-earth metals.