Tb Atoms Research Articles

Study on a Novel Structure of Terbium Complex, C<sub>6</sub>H<sub>14</sub>O<sub>19</sub>Tb<sub>2</sub>

The Tb complex C6H14O19Tb2 has been synthesized from a hydrothermal reaction and the crystal structure has been determined by means of single-crystal X-ray diffraction. The Tb atom is coordinated by nine O atoms. The molecular structure stabilized by the O-H…O hydrogen-bonding interactions.

Tb3Sn7: polymorphism and crystal structure of high-temperature modification

During the systematic investigation of the tin-rich side of the Tb-Sn binary system temperatures of non-variant transformations were established. The crystal structure of βTb3Sn7 was determined for the first time from single-crystal diffraction data. Parameters of the unit cell have been determined previously by Manfrinetti & Palenzona [(1993), J. Alloys Compd. 201, 43-47], but the structure was not solved until now. The compound belongs to a new structure type with space group Pmmm. The unit cell contains two split positions: Sn7 (Wyckoff 1a), Sn7A (Wyckoff 2q) and Sn8 (Wyckoff 1d), Sn8A (Wyckoff 2s). Structures of both α- and β-modifications of Tb3Sn7 can be described as close packing of the coordination polyhedra of Tb atoms. In turn these polyhedra can be constructed of fragments of simple AuCu3 and CsCl types.

The analysis of the magnetic properties and the electronic structure in the TbxGd1−xFe3 intermetallics

The polycrystalline compounds TbxGd1−xFe3 with a PuNi3 – type of crystal structure have been obtained. Based on wide-range SQUID magnetometer series of different magnetic measurements have been carried out. Moreover, magnetic properties in the paramagnetic range have been studied by means of the Faraday type magnetic balance. The partial replacement of Gd by Tb (Gd/Tb) atoms is reflected in the increase of magnetic parameters e.g. the increase of the saturation magnetic moment (MS) from 1.6 μB/f.u (x = 0.0) to 3.42 μB/f.u (x = 1.0). The study of the hysteresis loops has been performed in several chosen temperatures. A quite strong dependence of coercivity (HC) and remanent magnetization (Mr) on the temperature and the amount of Tb has been found. The exchange coupling parameters of R–R (ARR), T–T (ATT) and R-T (ART) have been evaluated from magnetization curves M(T) based on the mean field theory (MFT) calculations. The XPS spectra have been measured at the room temperature. The valence band spectra as well as the core level lines have been analyzed as the influence of Gd/Tb substitution on the electronic structure. The valence bands near the Fermi level (EF) are dominated by Fe3d states and indicate the increase of intensity of states for higher terbium content. A strong dependence of the magnetic properties on the changes within the electronic structure has been found.

Modeling of the Laser-Heating Induced Ultrafast Demagnetization Dynamics in Ferrimagnetic Thin Films

Ultrafast demagnetization excited by laser pulses introduces the technological possibility for controlling the magnetic properties of materials on sub-picosecond regime. In this paper, the demagnetization dynamics of amorphous ferrimagnetic TbFeCo alloy is modeled by using the stochastic Landau-Lifshitz-Gilbert equation on an atomistic level. The transition metal (Fe, Co) and rare earth (Tb) atoms are constructed by two different sub-lattice systems. Laser-heating induced demagnetization processes are clearly demonstrated by a series of snapshots. Our simulations show that full demagnetization on the sub-picosecond time scale requires a temperature over the Curie point, and the demagnetization time increases with the Tb content.

Coexistence of Ising and XY Spin Systems on a Single Tb Atom in TbCoGa5

The tetragonal compound TbCoGa5 exhibits two successive magnetic transitions at \(T_{\text{N1}}=36.2\) and \(T_{\text{N2}}=5.4\) K. The results of the measurement of the magnetic susceptibility and specific heat indicate that the \(c\)- and \(ab\)-components of the magnetic moments of Tb3+ show independent antiferromagnetic orderings at \(T_{\text{N1}}\) and \(T_{\text{N2}}\), respectively. In this work, we have investigated the physical properties of TbCoGa5 in a magnetic field. Single crystals of TbCoGa5 were grown and their specific heat, electrical resistivity, magnetization and elastic constant were measured. The magnetic exchange interactions in TbCoGa5 are discussed referring to the result of the magnetization process. Additionally, the present and previous results are summarized in a magnetic phase diagram. The magnetic phase diagram indicates that the behavior of \(T_{\text{N1}}\) in a changing magnetic field is similar to that of an Ising spin system, and the behavior of \(T_{\text{N2}}\) is similar to that of an XY spin system. Thus, we conclude that Ising and XY spin systems coexist on a single Tb atom in TbCoGa5.

Diffusion Processes in Early Stages of Precipitation in Mg-Gd and Mg-Tb Alloys

Early stages of precipitation were investigated in solution treated binary Mg-Tb and Mg-Gd alloys. The supersaturated solid solution of Gd (or Tb) in Mg was formed by fast quenching of the alloys from solution treatment temperature. Decomposition of the supersaturated solid solution and precipitation effects were investigated by positron lifetime spectroscopy combined with microhardness testing. During solution treatment at elevated temperature some thermal vacancies form pairs with solute atoms. In quenched samples free vacancies are quickly annealed out, while more stable vacancies bound to solute atoms remain in the sample and enhance the diffusivity of solutes. The hardness of solution treated Mg-Tb and Mg-Gd alloys aged at ambient temperature rises due to formation of small clusters of Tb and Gd atoms. Isochronal annealing of Mg-Tb and Mg-Gd alloys leads to precipitation of coherent β phase, semicoherent β phase and incoherent β phase particles. It was found that natural aging of Mg-Tb alloy at ambient temperature has beneficial effect on subsequent hardening by β phase particles formed during annealing.

1.3.2. Synthesis, crystal structure and thermal stability property of a new terbium(III) coordination polymer based on 2,5-thiophenedicarboxylic acid

Abstract: A new coordination polymer [Tb2L2(Ox)(H2O)4]n·nH2O (H2L = 2,5-thiophenedicarboxylic acid, H2Ox = Oxalicacid) has been synthesized under hydrothermal reaction andcharacterized by single crystal X-ray diffraction analysis, IRspectra, and thermogravimetric analyses. The two Tb atoms areeight-coordinated in a distorted dodecahedron geometry for Tb1and in a distorted bicapped trigonal prism geometry for Tb2.The structure possesses a 3D (3,8)-connected topology net withTb2(COO)2O12 SBUs and L2–, Ox2– ligands. The thermogravimetricproperty of 1 has been investigated.Supporting information: CIF file.

희토류 영구자석의 현황 및 개발 동향

고특성 영구자석은 하이브리드 및 전기자동차의 구동모터와 풍력발전에 적용되면서 크게 주목을 받고 있다. Nd-Fe-B 영구자석은 가장 높은 최대자기에너지적을 가지고 있지만 고온(~200 ℃)의 구동환경에서는 보자력이 급격히 감소하기 때문에 사용할 수 없는 단점을 가지고 있다. 그러므로 큰 보자력을 가지는 Nd-Fe-B 영구자석에 대한 개발이 요구되고 있다. Nd-Fe-B 소결자석에서 보자력을 증가시키기 위해서는 Nd를 Dy 또는 Tb으로 치환하면 쉽게 증가시킬 수 있다. 그러나 이들 원소는 Fe와 반강자성 결합을 하여 잔류자속밀도를 낮추고, 적은 매장량과 한정된 지역에 편재되어 있어 수요급증에 따른 자원수급 및 가격 급등의 문제를 가지고 있다. 따라서, Dy 및 Tb과 같은 중희토류를 사용하지 않거나 최소한의 양을 사용하여 보자력을 증가시키고자 하는 연구가 많이 진행되고 있다. 본 논문에서는 이러한 중희토류 원소의 저감 및 대체에 대한 연구들을 소개하고자 한다.

Tris(thiocyanato-κN)tris(triphenylphosphine oxide-κO)terbium(III)

The title compound, [Tb(NCS)3(C18H15OP)3], contains a six-coordinate TbII cation surrounded by three O-bound triphenyl­phosphine oxide ligands and three N-bound thio­cyanate ligands, each in a fac arrangement. There are two crystallographically unique TbIII atoms in the asymmetric unit. One TbIII atom resides on a threefold rotation axis, while the other has no imposed crystallographic symmetry. The thio­cyanate ligands are bound through N atoms, illustrating the hard–hard bonding principles of metal complex chemistry.

Natural aging of Mg–Gd and Mg–Tb alloys

AbstractSubstantial natural aging occurring on the time scale of less than 1 month was observed in solution‐treated Mg–Gd and Mg–Tb alloys. Solution treatment at 500 and 530 °C for Mg–Gd and Mg–Tb alloys, respectively, leads to dissolution of Gd or Tb in the Mg matrix. By quenching of solution‐treated alloys to room temperature a supersaturated solid solution of Gd or Tb in Mg was formed. During subsequent aging at ambient temperature the hardness of quenched alloys increases, most probably, due to agglomeration of dissolved Gd or Tb atoms into small clusters. Positron lifetime spectroscopy combined with coincident Doppler broadening revealed that quenched alloys contain vacancies bound to Gd or Tb atoms. Quenched‐in vacancies facilitate clustering of Gd or Tb solutes and disappear from the samples when the clusters are fully developed.

Magnetic and electronic properties of half-metallic NiTbSb: a first principles study

The electronic band structures, density of states (DOS) and the magnetic moments have been compared and analyzed to propose the half-metal ferromagnetic nature of NiTbSb. For this, density functional theory based full potential linearized augmented plane wave method has been used. DOS and band structure results show that 3d states of Ni and 4f states of Tb atoms overlap each other throughout the Ni-3d bands, suggesting substantial hybridization between them. The presence of Sb atom influences the hybridization between Ni and Tb atoms. A qualitative agreement with the earlier results has been observed.

Defect centers of rare-earth metals in a-Si(H)

Electrical and photoelectric properties of a-Si(H) films doped by rare-earth metals were investigated. Nd, Sm, Gd, Tb, Dy, Ho, and Yb dopant atoms were shown to generate an acceptor type band near to the middle of the mobility gap of a-Si(H). Eu dopant atoms generate a donor-type band in the mobility gap of a-Si(H). Eu, Dy and Yb dopant atoms intensify photoconduction of a-Si(H) whereas Nd, Sm, Gd, Tb, and Ho dopes inhibit the photoconduction.

Influence of Deformation on Precipitation Kinetics in Mg-Tb Alloy

Precipitation effects in age-hardenable Mg-13wt.%Tb alloy were investigated in this work. The solution treated alloy was subjected to isochronal annealing and decomposition of the supersaturated solid solution was investigated by positron annihilation spectroscopy combined with transmission electron microscopy, electrical resistometry, differential scanning calorimetry and microhardness measurements. Peak hardening was observed at 200°C due to precipitation of finely dispersed particles of β phase with the D019structure. Vacancy-like defects associated with β phase particles were detected by positron annihilation. At higher temperatures precipitation of β and subsequently β phase takes place. Formation of these phases lead to some additional hardening and introduces open volume defects at precipitate/matrix interfaces. To elucidate the effect of plastic deformation on the precipitation sequence we studied also a Mg-13wt.%Tb alloy with ultra fine grained structure prepared by high pressure torsion. In the ultra fine grained alloy precipitation of the β phase occurs at lower temperature compared to the coarse grained material and the peak hardening is shifted to a lower temperature as well. This effect can be explained by enhanced diffusivity of Mg and Tb atoms due to a dense network of grain boundaries and high density of dislocations introduced by severe plastic deformation. Moreover, dislocations and grain boundaries serve also as nucleation sites for precipitates. Hence, precipitation effects are accelerated in the alloy subjected to severe plastic deformation.

Tetraaquatetrakis(4,4′-bipyridine dioxide-κO)terbium(III) octacyanidotungstate(V)

In the title compound, [Tb(C10H8N2O2)4(H2O)4][W(CN)8], both metal atoms are eight-coordinated. The TbIII ion displays a dodeca­hedral geometry, while the Wv ion exhibits a distorted square-anti­prismatic geometry. The Tb atoms are located on a special position of site symmetry -4, whereas the W atoms are located on a twofold rotation axis. The cations are linked by O—H⋯O hydrogen bonds. The title compound is isotypic with the corresponding and previously described Mo compound [Qian & Yuan (2011 ▶). Acta Cryst. E67, m845].

Construction of three metal-organic frameworks based on multifunctional T-shaped tripodal ligands (4,5-dicarboxy-1H-imidazol-2-yl)pyridine-1-oxide

Three metal-organic frameworks, [Eu(C10H6N3O5)3(H2O)2] · H2O (1), [Tb(C10H6N3O5)3(H2O)2] · H2O (2), and [Cd(C10H6N3O5)2Cl2] (3) based on T-shaped tripodal ligands 3-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine-1-oxide and 4-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine-1-oxide (H3DCImPyO), have been synthesized by the hydrothermal method and characterized by elemental analysis, IR, and single-crystal X-ray structure analysis. The diverse coordination modes of H3DCImPyO ligands have afforded the three compounds. Complexes 1 and 2 are isomers and the Ln (Ln = Eu or Tb) atoms have coordination number eight with a distorted square prism geometry. The partly deprotonated H2DCImPyO− ligands display three different coordination modes to link Ln (Ln = Tb or Eu) into 1-D double chains. In 3, Cd(II) lies on an inversion center and displays a slightly distorted octahedral coordination. All three compounds exhibit strong fluorescent emissions in the solid state at room temperature.

Terbium (lithium zinc) distannide, TbLi1–xZnxSn2(x= 0.2)

The new terbium (lithium zinc) distannide, TbLi1–xZnxSn2 (x = 0.2) crystallizes in the ortho­rhom­bic CeNiSi2 structure type with space group Cmcm and Pearson symbol oS16. Of the four independent 4c atom positions (m2m site symmetry), three are fully occupied by individual atoms (two by Sn and one by Tb atoms) and the fourth is occupied by Li and Zn atoms with a statistical distribution. The Tb coordination polyhedron is a 21-vertex pseudo-Frank–Kasper polyhedron. One Sn atom is enclosed in a tricapped trigonal prism, the second Sn atom is in a cubocta­hedron and the statistically distributed (Li,Zn) site is in a tetra­gonal anti­prism with one added atom. Electronic structure calculations were used for the elucidation of reasons for and the ability of mutual substitution of lithium and transition metals. Positive charge density was observed around the rare earth atom and the Li and Zn atoms, the negative charge density in the proximity of the Sn atoms.

Local chemical and topological order in Al–Tb and its role in controlling nanocrystal formation

How the chemical and topological short- to medium-range order develops in Al–Tb glass and its ultimate effect on the control of the high number density of face-centered-cubic-Al (fcc-Al) nuclei during devitrification are described. A combined study using high-energy X-ray diffraction (HEXRD), atom probe tomography (APT), transmission electron microscopy and fluctuation electron microscopy (FEM) was conducted in order to resolve the local structure in amorphous Al90Tb10. Reverse Monte Carlo simulations and Voronoi tessellation analysis based on HEXRD experiments revealed a high coordination of Al around Tb atoms in both liquid and amorphous states. APT results show Al-rich and Al-depleted regions within the as-quenched alloy. A network structure of Tb-rich clusters divides the matrix into nanoscale regions where Al-rich clusters are isolated. It is this finely divided network which allows the amorphous structure to form. Al-rich regions are the locus for fcc-Al crystallization, which occurs before the intermetallic crystallization. FEM reveals medium-range ordered regions ∼2nm in diameter, consistent with fcc-Al and trigonal-like Al3Tb crystal structures. We propose that the high coordination of Al around Tb limits diffusion in the intermetallic network, allowing for the isolated Al-rich regions to form at high density. These regions are responsible for the extremely high density of Al nanocrystal nuclei.

Pentaterbium lithium tristannide, Tb5LiSn3

The new ternary phase penta­terbium lithium tris­tannide, Tb5LiSn3, crystallizes in the hexa­gonal Hf5CuSn3 structure type, which is a ‘filled’ version of the binary RE 5Sn3 phases (Mn5Si3-type) (RE is rare earth). The asymmetric unit contains two Tb sites (site symmetries 3.2 and m2m), one Li site (site symmetry .m) and one Sn site (site symmetry m2m). The 14-vertex Frank–Kasper polyhedra are typical for Li and Tb atoms. The environment of the Sn atom is a pseudo-Frank–Kasper polyhedron with a coordination number of 13 for the tin atom. One of the Tb atoms is enclosed in a 17-vertex polyhedron. The metallic type of bonding was indicated by an analysis of the inter­atomic distances.

Electronic structure, magnetic properties, and magnetostructural transition in Tb5Si2.2Ge1.8from first principles

The electronic structure and magnetic properties of Tb${}_{5}$Si${}_{2.2}$Ge${}_{1.8}$ have been studied from first principles electronic structure calculations. The total energy of the ferromagnetic (FM) orthorhombic [O(I)] Tb${}_{5}$Si${}_{2.2}$Ge${}_{1.8}$ is lower than the total energy of the FM monoclinic (M) Tb${}_{5}$Si${}_{2.2}$Ge${}_{1.8}$, indicating that the FM O(I) is the ground state structure of Tb${}_{5}$Si${}_{2.2}$Ge${}_{1.8}$. Because of a strong $4f$-$5d$ exchange, the splitting of $5d$ bands of Tb atoms in the FM O(I) Tb${}_{5}$Si${}_{2.2}$Ge${}_{1.8}$ is greater than that in the FM M Tb${}_{5}$Si${}_{2.2}$Ge${}_{1.8}$, giving rise to higher $5d$ moments in the former. The magnetostructural transition temperature, ${T}_{M}$, and the isothermal magnetic entropy change, \ensuremath{\Delta}${S}_{M}$, have been calculated by coupling the parameters obtained from the first principles to the magnetothermodynamic models. Both ${T}_{M}$ and $\ensuremath{\Delta}{S}_{M}$ are in good agreement with reported experimental values. The magnetic entropy change increases with decreasing magnetostructural transition temperature, which indicates a pathway toward tuning the magnitude of the magnetocaloric effect.

Tris(6-carboxypyridine-2-carboxylato)terbium(III) 2.75-hydrate

In the title compound, [Tb(C7H4NO4)3]·2.75H2O, the Tb3+ atom is coordinated by three tridentate 6-carb­oxy­pyridine-2-carboxyl­ate ligands and lies on a crystallographic threefold rotation axis. The coordination polyhedron around TbIII adopts a distorted tricapped trigonal–prismatic geometry. Disordered water mol­ecules with partial occupancy are also present in the crystal, one of which is associated with each of the carboxyl­ate O atoms of the complex unit.