Tm Substitution Research Articles

STRUCTURES, ELECTRONIC PROPERTIES AND DIPOLE MAGNITUDES OF TMWn−1O3n AND TM2Wn−2O3n (TM = Ni, Pd AND Pt; n=2−6) CLUSTERS

Transition metal substitution can expand the applications of tungsten oxides in chemical sensors, catalysts, and other fields. In order to highlight the effect of TM substitution on the electronic properties of tungsten oxide clusters, the configurations, electronic properties and dipole magnitudes of [Formula: see text] and [Formula: see text] (TM = Ni, Pd and Pt; [Formula: see text]) clusters have been investigated via the density functional theory. The structures of [Formula: see text] and [Formula: see text] clusters inherit those of [Formula: see text] ([Formula: see text] = 2–6) clusters to some extent except for [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] clusters. [Formula: see text] clusters exhibit higher thermodynamic stability than the other [Formula: see text] and [Formula: see text] clusters. [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] clusters display more kinetically stable than adjacent [Formula: see text] and [Formula: see text] clusters. The Mülliken charge transfer amount of [Formula: see text] clusters is more than that of other [Formula: see text] and [Formula: see text] clusters except for [Formula: see text] clusters.

Exploring the effect of partial RE (Nd, Eu, Tm) substitution on Sn sites on the electronic and physical properties of BaSnO3

We have studied with the help of density functional calculations of the structural, phonon, elastic, mechanical, thermodynamic, electronic and optical properties of pure and RE (Nd, Eu, Tm) substituted BaSnO3 compounds. For this purpose, we have been used VASP. Our calculated ground-state and elastic properties of BaSnO3 are consistent with available experimental and other theoretical results. The phonon spectrum and elastic modulus results confirmed that pure and RE substituted compounds are dynamic and mechanically stable. Our calculated results suggest that both pure and RE substituted compounds exhibited brittle behaviour. The free energy, entropy, heat capacity as a function of temperature from 0 K to 1000 K have been estimated and discussed. The optical properties such as the real and imaginary part of the dielectric constant, refractive index, reflectivity, absorption and energy loss function have been computed and discussed. In addition to this, the electronic band structure results reveal that RE substitution on BaSnO3 has changed the significant effect on the bandgap value. Our obtained electronic and optical results of these materials reflect that they are suitable for optoelectronic device applications.

Large magnetocaloric effect of Tm1 − xYxGa (0 ≤ x ≤0.8) compounds with second-order magnetic transition around liquid helium temperature

A systematic investigation about Tm substitution by rare earth Y atoms in Tm1 − xYxGa (0 ≤ x ≤0.8) compounds on the magnetic properties and magnetocaloric effect (MCE) is presented. Among Tm1 − xYxGa compounds, Tm0.4Y0.6Ga exhibits the optimized working temperatures around the boiling point of liquid helium and large MCE. It undergoes a ferromagnetic (FM) to antiferromagnetic (AFM) transition at TFA = 2.8 K and an AFM to paramagnetic transition at TN = 5.4 K with increasing temperature, respectively. Moreover, the characteristic of second-order magnetic transition was confirmed on the basis of Arrott plots, rescaled universal curves, mean-field theory criterion, and the quantitative criterion of exponent n. Large MCE with the maximum magnetic entropy change of 6.4, 10.1, and 15.6 J/kg K and the maximum adiabatic temperature change of 2.4, 4.2, and 8.4 K for the field changes of 0–1, 0–2, and 0–5 T was observed, respectively. Consequently, the properties of low working temperatures, the characteristic of second-order magnetic transition, and good performance of MCE indicate that Tm0.4Y0.6Ga compounds could be a promising candidate of magnetocaloric materials in the application of helium liquefaction.

Enhanced dielectric, ferroelectric, and ferromagnetic properties of 0.7Bi1−xTmxFeO3–0.3BaTiO3 ceramics by Tm-induced structural modification

In this study, Tm-doped 0.7Bi1−xTmxFeO3–0.3BaTiO3 (x = 0–0.05) ceramics have been fabricated using traditional solid-phase reactions and their structural, morphological, and dielectric as well as multiferroic properties are investigated. X-ray diffraction and Rietveld refinement indicated the formation of a Tm-modulated morphotropic phase boundary (MPB) from the rhombohedral (R3c) and tetragonal (P4mm) phases to a single P4mm phase for Tm content of x = 0.02–0.03. Tm occupation of lattice sites is strongly suggested at both the A and B sites in the ABO3-type perovskite structure, which is supported by the obtained Raman spectra, the calculated tolerance factor, and dielectric relaxation characteristics. With the Tm-induced aforementioned–structural modification, the dielectric constant, remnant polarization (Pr), and remnant magnetization (Mr) values indicate that the dielectric and multiferroic properties are greatly improved. The obtained maximum remnant polarization (2Pr = 35.28 μC/cm2) and remnant magnetization (2Mr = 0.56 emu/g) are approximately two and seven times larger, respectively, than those of the sample without Tm substitution (x = 0). With increasing the Tm content, the remnant polarization, and the remnant magnetization exhibit almost the same trends in variation, indicating the possible existence of a relatively strong magnetoelectric coupling effect. Our study may provide a substitution strategy (structural modification by substituting the same element into two different lattice sites) to efficiently enhance the dielectric and multiferroic properties of BiFeO3–BaTiO3-based ceramics.

Structural, magnetic, optical properties and cation distribution of nanosized Co0.7Zn0.3TmxFe2-xO4 (0.0 ≤ x ≤ 0.04) spinel ferrites synthesized by ultrasonic irradiation.

This study expressed the influence of Tm substitution on the structural, optical and magnetic properties of Co-Zn spinel ferrites (Co0.7Zn0.3TmxFe2-xO4 (0.0 ≤ x ≤ 0.04)). The different compositions were synthesized by sonochemical method using Qsonica ultrasonic homogenizer, frequency: 20 kHz and power: 70 W for 60 min. XRD patterns proved the presence of single-phase spinel ferrites with crystallites size in the 8-10 nm range. Cation distribution approved the occupancy of octahedral (B) site by Tm. The morphology and the elements stoichiometry are obtainable through FE-SEM, EDX and elemental mapping. Optical band gap (Eg) values were estimated via DR % (percent diffuse reflectance) investigations and Kubelka-Munk theory. Tauc plots revealed that direct Eg values are ranging between 1.49 and 1.68 eV. The analyses of magnetization versus magnetic field, M(H), were performed. The following magnetic parameters like saturation magnetization Ms, squareness ratio (SQR = Mr/Ms), magnetic moment nB, coercivity Hc and remanence Mr have been evaluated. M(H) curves revealed the superparamagnetic (SP) at RT and ferromagnetic property at 10 K. It was showed that the Tm3+ substitutions significantly affect the magnetic properties of host spinel ferrites. An increasing trend in the Ms, Mr, Hc, and nB values was noticed for lower Tm3+ substitution content.

Effect of thulium substitution on conductivity and dielectric belongings of nanospinel cobalt ferrite

The CoTmxFe2−xO4(x ≤ 0.1) NPs were synthesized sonochemically. X-ray powder diffraction patterns and TEM images of the samples prove their chemical purity and cubic structure-morphology, respectively. Some substitution ratio of thulium ions to cobalt ferrites have an important effect on the characteristic evaluation of both electrical and dielectric characteristic measured at frequencies up to 3.0 MHz between room temperature and 120 °C. Since the thulium substitution has a very strong effect on the characteristic evaluation of both electrical and dielectric properties of cobalt-ferrite samples, four substitutional ranges - none, small, medium and high were determined for the interpretation of contribution of thulium ratio to ac/dc conductivity, dielectric constant, dielectric loss and tangent loss. Conductivity increases with the incremental frequencies, in general depending on a variety of tendencies of both temperature and substitutional Tm ratios while the activation energy varies with a high dependency to the regional level of Tm substitution in Co-ferrites NPs. The Arrhenius graph appears to provide us with a single activation energy much higher than 400 meV for x = 0.02, which can be attributed to electron hopping mechanisms, apart from other substituted spinel ferrites.

Superconductivity in Te-deficient polymorphic MoTe2−x and its derivatives: rich structural and electronic phase transitions

The group 6 transition metal dichalcogenides (TMDs) have been received great attentions due to intriguing superconducting states correlated with structural uncertainty and electronic complexity. Here, we synthesized Te-deficient polycrystals of semimetallic MoTe2−x and its derivatives (Mo1−yTMyTe2−xChx(TM: Nb, Mn and V, Ch: P)), and investigated the structural and electronic phase transitions. It was found that all Te-deficient semimetallic phases (monoclinic 1T′, hexagonal 2H and rhombohedral 3R) exhibited the superconducting transition, in which 2H and 3R structures were evolved in Nb-substituted Mo1−yNbyTe2−x (y = 0.4 for 2H, 0.6 for 3R), respectively. Moreover, we found that the superconducting state of 2H-and 3R-Mo1−yNbyTe2−x appears at the vicinity of the transition from insulator to semimetal regime with the increased electron concentration via TM substitution and Te-deficiency. It is revealed that all superconducting 1T′-, 2H- and 3R-Mo1−yTMyTe2−xChx semimetals show the half-dome shaped superconducting phase diagram with respect to the electron concentration and TM substitution.

Study on the structural and electromagnetic properties of Tm-substituted Mg–Mn ferrites by a solution combustion method

The effect of thulium ion substitution for iron on the structural and electromagnetic properties of Mg–Mn ferrites is reported. The Mg0.9Mn0.1TmxFe1.8−xO4 ferrite compositions with x=0.0, 0.025, 0.05, and 0.075 were synthesized by a nitrate–citrate solution combustion method. Tm substitution had taken place and this was found to produce a secondary phase TmFeO3. The crystallite size of the powder calcined at 500°C was in the range of 9–13nm. Subsequently, the calcined ferrite powders were compacted and sintered at 1250°C. It was found that the physical and magnetic properties had changed with Tm contents. Bulk density was found to decrease from 4.26 to 3.82g/cm3 with increasing Tm contents. It was also found that the saturation magnetization (Ms=38.41–23.62emu/g) had decreased with an increase of Tm. In this study, the highest resistivity (39.84×106Ωcm) was observed for Mg0.9Mn0.1Fe1.725Tm0.075O4. The correlation between structural and electromagnetic properties of the Tm-substituted samples is interpreted based on phase composition as well as microstructure.

Conserved Allosteric Hot Spots in the Transmembrane Domains of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Channels and Multidrug Resistance Protein (MRP) Pumps

ATP-binding cassette (ABC) transporters are an ancient family of transmembrane proteins that utilize ATPase activity to move substrates across cell membranes. The ABCC subfamily of the ABC transporters includes active drug exporters (the multidrug resistance proteins (MRPs)) and a unique ATP-gated ion channel (cystic fibrosis transmembrane conductance regulator (CFTR)). The CFTR channel shares gating principles with conventional ligand-gated ion channels, but the allosteric network that couples ATP binding at its nucleotide binding domains (NBDs) with conformational changes in its transmembrane helices (TMs) is poorly defined. It is also unclear whether the mechanisms that govern CFTR gating are conserved with the thermodynamically distinct MRPs. Here we report a new class of gain of function (GOF) mutation of a conserved proline at the base of the pore-lining TM6. Multiple substitutions of this proline promoted ATP-free CFTR activity and activation by the weak agonist, 5'-adenylyl-β,γ-imidodiphosphate (AMP-PNP). TM6 proline mutations exhibited additive GOF effects when combined with a previously reported GOF mutation located in an outer collar of TMs that surrounds the pore-lining TMs. Each TM substitution allosterically rescued the ATP sensitivity of CFTR gating when introduced into an NBD mutant with defective ATP binding. Both classes of GOF mutations also rescued defective drug export by a yeast MRP (Yor1p) with ATP binding defects in its NBDs. We conclude that the conserved TM6 proline helps set the energy barrier to both CFTR channel opening and MRP-mediated drug efflux and that CFTR channels and MRP pumps utilize similar allosteric mechanisms for coupling conformational changes in their translocation pathways to ATP binding at their NBDs.

Possible undercompensation effect in the Kondo insulator (Yb,Tm)B12

The effects of Tm substitution on the dynamical magnetic response of Yb${}_{1\ensuremath{-}x}$Tm${}_{x}$B${}_{12}$ $(x=0$, 0.08, 0.15, and 0.75) and Lu${}_{0.92}$Tm${}_{0.08}$B${}_{12}$ compounds have been studied using time-of-flight inelastic neutron scattering. Major changes were observed in the spectral structure and temperature evolution of the Yb contribution to the inelastic response for a rather low content of magnetic Tm ions. A sizable influence of the $R$B${}_{12}$ host (YbB${}_{12}$, as compared to LuB${}_{12}$ or pure TmB${}_{12}$) on the crystal-field splitting of the Tm${}^{3+}$ ion is also reported. The results point to a specific effect of impurities carrying a magnetic moment (Tm, as compared to Lu or Zr) in a Kondo insulator, which is thought to reflect the ``undercompensation'' of Yb magnetic moments, originally Kondo screened in pure YbB${}_{12}$. A parallel is made with the strong effect of Tm substitution on the temperature dependence of the Seebeck coefficient in Yb${}_{1\ensuremath{-}x}$Tm${}_{x}$B${}_{12}$, which was reported previously.

Conditions and possibilities of direct utilisation of thermal-mineral waters in Raska region, Serbia

The natural thermal-mineral springs in the Raska region in Serbia have been known since the ancient period. Temperatures of these sources between 26 °C and 51 °C have allowed the use of water for balneology and recreational purposes. Research over the past 50 years have pointed to the existence of significant amounts of thermal-mineral waters that occur in different tectonic zones and faults in the Dinarides. Bearing in mind the properties of thermal-mineral waters the paper deals with possibilities of their use as a renewable resource. The paper analyses the way of use of waters in three spas and one spring for health and recreational purposes and presents the possibilities for improving the use of unused water. The results hint at the possibility of direct use of heat energy from TM sources and substitution of fossil fuels, expenses of living and work in local communities. Direct use of geothermal energy, especially during the colder period of the year, would reduce the expenses of heating of public institutions, services and private households.

Effects of Transition Metal (TM: Co, Rh, Ni and Pd) Substitution for Ru on Thermoelectric Properties for Intermetallic Compound RuGa<sub>2</sub>

The effects of substituting transition metals (TM: Co, Rh, Ni and Pd) on the Ru site with respect to the electrical conductivity and Seebeck coefficient for the binary semiconducting intermetallic compound RuGa2 have been investigated above room temperature. Only Rh substituted RuGa2 exhibited a higher electrical conductivity compared with undoped RuGa2. The sign of the Seebeck coefficient at 373K for all doped samples is negative and their magnitudes exhibit rather large values of 150 < «S373K« < 350μVK11, indicating that Co, Rh, Ni and Pd work as n-type dopants. However, the sign changes from negative to positive at high temperature. This implies that the effective carrier doping is insufficient to obtain a high efficiency n-type material. To investigate the effect of TM substitution on the electronic density of states, the Korringa-Kohn-Rostoker Green’s function method under a coherent potential approximation has been employed. The calculation indicates that the dopant d-states at the conduction band affect the transport properties. [doi:10.2320/matertrans.E-M2013804]

The Effect of Tm Substitution on the Thermoelectric Performance of Yb&lt;SUB&gt;14&lt;/SUB&gt;MnSb&lt;SUB&gt;11&lt;/SUB&gt;

The Effect of Tm Substitution on the Thermoelectric Performance of Yb&lt;SUB&gt;14&lt;/SUB&gt;MnSb&lt;SUB&gt;11&lt;/SUB&gt;

Element Substitution Effect in Transition Metal Oxypnictide Re(O1-xFx)TAs (Re = rare earth, T = transition metal)

Different element substitution effects in transition metal oxypnictide Re(O1-xFx)TAs, with Re = La, Ce, Nd, Eu, Gd, Tm, T = Fe, Ni, Ru, are studied. Similar to the La- or Ce-based systems, we find that the pure NdOFeAs shows a strong resistivity anomaly near 145 K, which is ascribed to the spin-density-wave instability. Electron doping by F increases Tc to about 50 K. While in the case of Gd, Tc is reduced below 10 K. The tetragonal ZrCuSiAs-type structure could not be formed for Eu or Tm substitution in our preparing process. For the Ni-based case, although both pure and F-doped LaONiAs are superconducting, no superconductivity is found when La is replaced by Ce in both the cases, instead a ferromagnetic ordering transition is likely to form at low temperature in the undoped sample. We also synthesize LaO1-xFxRuAs and CeO1-xFxRuAs compounds. The metallic behaviour is observed down to 4K.

Effect of Tm substitution on the magnetic and magnetocaloric properties in the intermetallic compounds (Tb1−xTmx)Co2

The magnetic and magnetocaloric properties of the intermetallic compounds Tb1−xTmxCo2 (with x = 0, 0.2 and 0.5) have been studied. It is found that partial replacement of Tb by Tm in TbCo2 leads to a reduction in the ordering temperature, which is attributed to the decrease in the exchange strength due to the lower spin value of Tm3+ as compared with that of Tb3+. The analysis of the zero-field heat capacity data at low temperature shows that the coefficient of electronic heat capacity increases with increase in Tm content and is attributed to the presence of local spin fluctuations. The variation of the magnetocaloric effect (MCE) has been explained on the basis of the magnetic properties. Temperature dependence of the MCE shows that this system may be useful for magnetic refrigeration applications in a sub-room temperature regime.

Micro-pulling-down growth and characterization of Tb 3− xTm xAl 5O 12 fiber crystals for Faraday rotator applications

The effect of the thulium (Tm) substitution in the Tb 3Al 5O 12, Tb 3− x Tm x Al 5O 12 (TTAG) mixed garnet crystals, has been studied by the solidification of corresponding stoichiometric melts using a micro-pulling down apparatus. The phase composition for the TTAG crystals with different Tm 3+ concentrations was determined by powder X-ray diffraction analysis. The amount of the TbAlO 3 perovskite phase in the as-grown TTAG fibers was observed to decrease with substitution of Tm 3+ in Tb 3+ site. The lattice parameters of the TTAG were reduced with increase of concentration of Tm 3+. The results of the Verdet constant measurements are also reported.

Inducing Magnetism in Wide Band Gap Hosts

ABSTRACTWe have used precursor routes to prepare magnetic transition metal ion (tM) substituted wurtzite ZnO powders with up to 15% tM substitution (tM = Co and Mn) on the cation site. Careful magnetic studies reveal these samples show no cooperative magnetic ordering, and certainly no ferromagnetism. Instead, the nearest-neighbor coupling is actually antiferromagnetic. Modeling of the temperature dependence of the magnetic susceptibility indicates the difficulty in inducing ferromagnetism, in keeping with the results of density functional calculations. The alternate strategy of inducing dilute ferri magnetism in wide band gap spinel hosts with two cation sites has been more successful; dilute magnets based on tM substitution in spinel ZnGa2O4 seem promising, displaying magnetic hysteresis in nearly transparent samples.

Preparation of overdoped superconducting (Ba,Sr) 2TmCu 3O z

A series of Ba 2− x Sr x RCu 3O z (R=Y or Tm) is annealed at various oxygen pressures to study the relationships between oxygen content, superconducting critical temperature ( T c) and x. The BaSrYCu 3O z cuprates annealed at various oxygen pressures are optimally doped. On the other hand, the T c of the BaSrTmCu 3O z cuprates annealed in air is reduced by 4 K after the annealing at 0.5 MPa of oxygen. The T c reduction is attributable to a slight increase in oxygen content by oxygenation. The BaSrTmCu 3O z cuprate annealed in oxygen is lightly overdoped. The replacement of Y by Tm and partial substitution of Ba by Sr increase the number of mobile holes in the CuO 2 sheet.

Temperature-dependent magnetic properties of (Y,Sm,Lu,Tm,Ca)3(Fe,Ge)5O12 epitaxial garnet films

Thulium has been substituted for yttrium in melts for the growth of (Y,Sm,Lu,Ca)3(Fe,Ge)5O12 epitaxial garnet films for the purpose of reducing the magnitude of the temperature coefficient αbc of the bubble collapse field. As an extension of previous substitutions [J. E. Davies, G. Galli, and J. C. Suits, J. Appl. Phys. 49, 1859 (1978)] of Tm for Lu to smaller bubble diameters, growth conditions were adjusted to produce films of nearly identical thickness (1.40 μm) and characteristic length (0.222 μm at 25°C) for Tm substitutions up to 0.25 atoms in the formula unit. This substitution was found to decrease the magnitude of αbc as measured at 50°C by approximately 0.04%/°C⋅Tm atom. Anisotropy remains nearly constant with Tm substitution.