Rare Earth Elements Yb Research Articles

Ferromagnetic half-metallic characteristic and phase transition in rare-earth Yb doped SiC: A GGA+U study

The electronic, magnetic and structural properties of rare earth Yb doped on SiC are investigated theoretically based on the density functional theory (DFT). Both zincblende (ZB) and rocksalt (RS) structures of SiC have been calculated. We found that Si3YbC4 with ZB exhibits a complete half-metallic characteristic with a wide gap more than 1.8eV using GGA and GGA+U methods. However, the half-metallicity is destroyed with RS. The sensitivity of magnetic moments of Si3YbC4 as a function of pressure is also discussed, there are two magnetic phase transition points with increased pressure. The exchange interaction between local Yb-4f electrons and conduction electrons plays an important role in their heavy fermion characters. The exchange splitting of the conduction band is confirmed to be much larger than that of the valence band in Si3YbC4, which makes the holes-mediated ferromagnetism in this material.

One-pot hydrothermal synthesis of lanthanide ions doped one-dimensional upconversion submicrocrystals and their potential application in vivo CT imaging

Multi-functional rare-earth Yb(3+) and Ln(3+) (Ln = Er, Tm and Ho) ions doped one-dimensional (1-D) upconversion submicrocrystals (NaYF(4) and NaGdF(4)) possessing upconversion luminescence, biocompatibility and magnetic properties have been synthesized by a one-pot hydrothermal method. Rare-earth Yb(3+) and Ln(3+) ions doped NaYF(4) microrods (~1 μm in diameter, 3-5 μm in length) exhibit porous properties, and the average pore sizes are ~28.2 nm. They show paramagnetism in the magnetic range of -60 to -2 kOe and 2 to 60 kOe at 300 K, and exhibit near superparamagnetic behaviour at the magnetic range of -2 to 2 kOe. Saturation magnetization was ~12.1 emu g(-1) at 2 K. The Yb(3+) and Ln(3+) ions doped NaGdF(4) submicrocrystals (~100 nm in diameter, 200-300 nm in length) show paramagnetism at 300 K, and exhibit superparamagnetic behaviour with a saturation magnetization of 129.2 emu g(-1) at 2 K. The magnetic properties of Yb(3+) and Ln(3+) ions doped 1-D upconversion submicrocrystals indicate they can be used for drug targeting under a magnetic field. Their unique upconversion emission (green for Yb(3+)/Er(3+) and blue for Yb(3+)/Tm(3+)) under 980 nm laser excitation indicate that they could be used for specific luminescent immunolabeling and imaging. MTT assays reveal that 1-D upconversion submicrocrystals have satisfactory bio-affinity, where the viability keeps in good state even at a concentration of 500 μg mL(-1), which is much higher than the concentration usually used in cell labelling. Luminescent microscopy images show that the morphologies of the cytoskeleton and cell nucleus are well maintained after incubating different concentrations of 1-D upconversion submicrocrystals. After injecting upconversion submicrocrystals into the mice (tumor sites or back normal tissue), a clearly distinguished CT signal was observed, indicating the synthesized 1-D submicrocrystals are effective for CT imaging in vivo.

Preparation, Structure and Near-infrared Luminescent Property of Yb(III) Complex with 2,4,6-Pyridinetricarboxylic Acid

A rare earth ytterbium complex with 2,4,6-pyridinetricarboxylic acid (H(3)pta) has been synthesized by hydrothermal method, the formula is {[Yb(2)(pta)(2)(H(2)O)(3)]·H(2)O}(n). The complex crystallized in monoclinic system, P2(1)/c space group with lattice parameters a = 11.6556(19)Å, b = 7.8364(12), c = 22.020(4), α = γ = 90º, β = 92.120(3), Z = 4, GOF = 1.026, R1 = 0.0334, wR2 = 0.0660. The pta anions connect four rare earth Yb(III) ions with two different coordination modes. The complex exhibit intense characteristic near-infrared luminescence of Yb(III) ions at 990 nm with excitation of UV-rays.

Mechanisms of the Magneto-Optical Activity of Rare-Earth Ions in Rare-Earth Iron Garnet Single Crystals

The magnetic and magneto-optical properties of the typical representatives of three rare-earth iron garnets (RIG) groups: with heavy rare-earth elements Yb, Er, Dy, Tb; with elements from the middle of lanthanide series Gd, Sm, and with light rare-earth element Nd are presented. In contradistinction to other work on the Faraday rotation, which were done only at 1152 nm (8696 cm−1), here we present FR spectra obtained in the energy region 5500–20000 cm−1 with high optical resolution. The investigations have been done at temperatures of 5, 82, 130, 295 K using magnetic field up to 25 kOe applied parallel to the [111] crystallographic axis of the crystals. It has been shown that the contribution proportional to the magnetic field and independent of temperature to the mixing of the ground state multiplets exceeds the paramagnetic contribution in YbIG, ErIG, GdIG, SmIG. In Tb and Dy iron garnets contributions from the two mechanisms have opposite signs, and the paramagnetic mechanism gives the greatest contribution to the Faraday rotation. Nevertheless, the contribution of the diamagnetic mechanism, caused by the influence of the exchange field in the iron sublattices on rare-earth ions, is significant, and it is necessary to take it into account. Anomalously large magneto-optical activity is observed in NdYIG. This is the result of contributions of the same sign and approximately equal in magnitude from the paramagnetic and diamagnetic mechanisms.

Effect of rare earth Yb addition on mechanical properties of Al–5·3Cu–0·8Mg–0·6Ag alloy

The precipitation hardening response, microstructure and mechanical properties of three Al–5·3Cu–0·8Mg–0·6Ag based alloys containing 0, 0·15 and 0·25 wt-%Yb were investigated using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. It is shown that increasing Yb content from 0 to 0·25 wt-% increased the tensile strength at all test temperatures up to 300 °C. The high strength of the alloys with Yb is attributed to the high density and high thermal stability of fine Ω precipitates.

The investigation of mechanisms of the magneto-optical activity of rare-earth iron garnet single crystals

The magnetic and magneto-optical properties (MO) of the typical representatives of three rare-earth iron garnets (RIG) groups: (1) with heavy rare-earth elements Yb, Er, Dy, Tb; (2) with elements from the middle of lanthanide series Gd, Sm; (3) with light rare-earth element Nd are presented. In contradistinction to other work on the Faraday rotation (FR), which were done only at 1152 nm (8696 cm −1); here, we present FR spectra obtained in the energy region 5500–20,000 cm −1 with high optical resolution. The investigations have been done at temperatures of 5, 82, 130 and 295 K using magnetic field up to 25 kOe applied parallel to the [1 1 1] crystallographic axis of the crystals. It has been shown that the contribution proportional to the magnetic field and independent of temperature to the mixing of the ground state multiplets exceeds the paramagnetic contribution in YbIG, ErIG, GdIG and SmIG. In Tb and Dy iron garnets contributions from the two mechanisms have opposite signs, and the paramagnetic mechanism gives the greatest contribution to FR. Nevertheless, the contribution of the diamagnetic mechanism, caused by the influence of the exchange field in the iron-sublattices on R ions, is significant, and it is necessary to take it into account. Anomalously large MO activity is observed in NdYIG. This is the result of contributions of in the same sign and approximately equal magnitude from the paramagnetic and diamagnetic mechanisms.

Electron-induced luminescence of SrCe 0.95Yb 0.05O 3−[formula omitted

Radioluminescence of perovskite-type oxide ceramics doped with rare-earth Yb 3+ ions (SrCe 0.95Yb 0.05O 3− δ ) was observed under irradiation with 1.8 MeV electrons at dose rates of 300 Gy/s at room temperature. Wide asymmetrical emission bands, associated with charge transfer vibronic exciton (CTVE) between O 2− and Ce 4+, oxygen vacancies with one or two trapped electrons and defects created due to dopant Yb 3+ ions, kept on producing in the ultraviolet (200–400 nm) and visible (400–800 nm) regions up to dose of 7.6 MGy. The result indicates that Yb-doped SrCeO 3 may be suitable as a material for radiation-induced luminescence. It was also found that the electron-induced luminescence in 500–650 nm at 7.6 MGy was apparently enhanced by annihilation of some absorption bands, due to reduction of Ce 4+ by irradiation.

Efficient magneto-optical trapping of Yb atoms with a violet laser diode

We report the first efficient trapping of rare-earth Yb atoms with a high-power violet laser diode (LD). An injection-locked violet LD with a 25 mW frequency-stabilized output was used for the magneto-optical trapping (MOT) of fermionic as well as bosonic Yb isotopes. A typical number of $4\times 10^6$ atoms for $^{174}$Yb with a trap density of $\sim 1\times10^8/$cm$^3$ was obtained. A 10 mW violet external-cavity LD (ECLD) was used for the one-dimensional (1D) slowing of an effusive Yb atomic beam without a Zeeman slower resulting in a 35-fold increase in the number of trapped atoms. The overall characteristics of our compact violet MOT, e.g., the loss time of 1 s, the loading time of 400 ms, and the cloud temperature of 0.7 mK, are comparable to those in previously reported violet Yb MOTs, yet with a greatly reduced cost and complexity of the experiment.

High field optical studies on intra-4f-shell photoluminescence in bulk growth Yb doped InP

Rare-earth Yb doped InP bulk crystal was grown by modified Bridgman method. Temperature dependence and magnetic field dependence of photoluminescence measurements were performed and found that the bulk growth InP:Yb shows very high efficiency of photoluminescence. From the temperature dependence, mechanism of the intra-4f-shell PL was discussed.

Electronic Structure of Si Doped by Rare-Earth Yb3+

ABSTRACTThe electronic structure of Yb3+-doped Si is elucidated in terms of level repulsion between the Si vacancy's deep levels (and spectral density) and the Yb3+ levels, both for bulk Si and for small clusters. The 2F5/2 level of Yb3+ splits into a Γ8 level and a Γ6 level, with the Γ6 repelled most, by the nearby Γ6 (A1) level of the Si vacancy. The level-repulsion is either upwards or downwards in energy, depending on whether the Al-like vacancy level lies below or above this Yb3+ level. The 2F7/2 Yb 3+ level is split into Γ6, Γ7, and Γ8 sub-levels, all moving downwards in energy, with Γ6 moving most, again due to strong level repulsion from the nearby Al-like vacancy level, while the more-distant, higher-energy T2-like (Γ7 and Γ8) vacancy level produces a weaker repulsion. In small clusters, the Si-vacancy's wavefunctions and deep level energies are sensitive to cluster-size, and changes in them alter the level repulsion experienced by the Yb 3+ levels, even though the 4f electrons are localized.

Near-infrared Yb 3+ vibronic sideband spectroscopy: application to Ca 2+-binding proteins

We have used near-infrared (NIR) vibronic fluorescence spectroscopy to study the vibrational structure of ligands associated with model complexes of the lanthanide Yb 3+. This technique exploits the similar binding properties of the lanthanide Yb 3+ to probe Ca 2+-binding sites in proteins. The (NIR) fluorescence of complexed Yb 3+ exhibits, in addition to main 0-0 ( 2F 5 2 → 2F 7 2 ) electronic transition of Yb 3+, weak vibronic sidebands which provide infrared-like, local vibrational spectra of the chelates (inner sphere ligands) of Yb 3+. A similar approach has been used for the lanthanide Gd 3+ (MacGregor, R.B. Jr. (1989) Arch. Biochem. Biophys. 274, 312–316) which fluoresces in the UV and which is usually complicated by amino-acid residues fluorescing in the same spectral region. In this same spectral region, other complications in studying photosynthetic membranes occur in the form of the excitation wavelength being actinic, promoting photodegradation of the membranes, as well as the reabsorption of Gd 3+ fluorescence. NIR excitation and fluorescence detection of Yb 3+ avoid these problems when studying photosynthetic membranes. A preliminary study has been conducted here on rat muscle parvalbumin.

Thermal stability and microstructure of the electrodeposited amorphous Fe 80P 18Yb 2 alloy

The thermal stability and microstructure of the electrodeposited amorphous Fe 80P 18Yb 2 alloy have been investigated by means of DSC and TEM. The microstructure observation reveals that during the crystallization process crystal grains grow at the cost of clusters. The crystallization kinetics parameters are obtained by J-M-A analysis based on DSC curves with different heating rates. In order to study the effect of adding the rare earth element Yb to amorphous FeP binary alloys, the relative fracture strain-brittleness parameter ϵ f and Hruby's K gl factor of our samples are also calculated in this paper. Results show that both thermal stability and ductility of the amorphous Fe 80P 18Yb 2 alloy are improved considerably compared with that of the amorphous Fe 81.5P 18.5 alloy. This offers favorable perspectives for the application of amorphous alloys in the future.

A Systematic investigation of the dc electrical conductivity of rare-earth doped ceria

The dc electrical conductivity of rare-earth doped ceria has been measured as a function of temperature (300–600 K) and composition (0.05–15 mol% M2O3) on using the complex impedance technique. Five dopants have been selected, yttrium and the lanthanides Yb, Gd, Nd, and La. For all of them, the variations of the activation energy versus dopant concentration are similar and characterized by the existence of a minimum. This peculiar property can be understood if attractive interactions between immobile dopant ions and mobile oxygen vacancies are taken into account. From an analysis of the experimental results, it is concluded that this interaction extends at least to third or fourth nearest neighbors depending on the size and the electronic configuration of the dopant ion.

Nonmonotonic evolution and thermodynamic trends at metal/(Hg,Cd)Te interfaces: Yb/Hg0.78Cd0.22Te

The microscopic interaction of cleaved Hg0.78Cd0.22Te surfaces with the highly reactive rare earth Yb was studied by use of photoemission spectroscopy and synchrotron radiation. We compare the results of this study with our previous investigation of Sm/(Hg,Cd)Te interface formation. Yb and Sm are similar in their initial stage of interface formation: rapid attenuation and near loss of the Hg emission is followed by its dramatic recovery. However, differences in valency between Sm and Yb develop during metal deposition and subsequently lead to differences in interface morphology. Calculated heats of solution are shown to correlate with the different behaviors observed during rare earth/(Hg,Cd)Te interface formation.

An optical stopped-flow and 1H and 113Cd nuclear magnetic resonance study of the kinetics and stoichiometry of the interaction of the lanthanide Yb3+ with carp parvalbumin.

The rate constants for the dissociation of the lanthanide Yb3+ from the CD and EF calcium-binding sites of carp parvalbumin (isoelectric point, 4.25) have been measured using optical stopped-flow and 1H nuclear magnetic resonance (NMR) methods. The off-rate constants for Yb3+ are 1.5 X 10(-1) and 1.3 X 10(-3) s-1, respectively, at pH 6.6 and 23 degrees C. The relative displacement of Ca2+ from the two sites by Yb3+ was determined from the observed amplitude of the fast and slow kinetic phases. Yb3+-shifted 1H-NMR spectra of parvalbumin are presented as a function of pH, concentration, and H2O:D2O ratio to relate the NMR results to the kinetic and optical results. The displacement of Cd2+ from parvalbumin by Yb3+ was studied using 113Cd NMR. All of the results show the sequential displacement of Ca2+ from the CD and EF sites of parvalbumin by Yb3+. Some results are also presented for Tb3+ and Gd3+.

New fluoride glasses based on 4f and 5f elements

New fluoride glasses have been isolated in the ternary systems ThF4-LnF3-BaF2 with Ln = the lanthanides Yb, Y, Tm. The melt must be quenched to reduce crystallization. They are simply prepared from oxides by an appropriate NH4F, HF treatment. The IR transmission is remarkable, the optical window lying in the 0.25-10 μm region.