Tb Compounds Research Articles

Magnetism and magnetocaloric effect in YNi 4 Si-type R Ni 4 Si ( R =Ce, Gd, Tb and Dy) compounds

Abstract Magnetic properties and magnetocaloric effect of YNi 4 Si-type R Ni 4 Si ( R =Ce, Gd, Tb and Dy) compounds have been investigated. Magnetic measurements indicate the intermediate valence state of cerium in YNi 4 Si-type CeNi 4 Si. The magnetocaloric effect of GdNi 4 Si, TbNi 4 Si and DyNi 4 Si are calculated in terms of isothermal magnetic entropy change and they reach maximum values of −22.9 J/kg K, −13.5 J/kg K and −15.6 J/kg K for a field change of 140 kOe near ~28 K, 47 K and 27 K and they show maximum values of −12.7 J/kg K, −7.8 J/kg K and −9.3 J/kg K for a field change of 50 kOe near ~28 K, 42 K and 22 K, respectively. In contrast to GdNi 4 Si, the magnetization-field isotherms for TbNi 4 Si and DyNi 4 Si exhibit hysteresis loop at 2 K due to strong magnetocrystalline anisotropy.

Structural magnetic and magnetostrictive properties of Tb0.3Dy0.7−xNdxFe1.93 [x = 0, 0.05, 0.1, 0.15 and 0.2] compounds

We report on the results pertinent to structural, magnetic, magnetostrictive studies of the Tb0.3Dy0.7−xNdxFe1.93 [x=0, 0.05, 0.1, 0.15 and 0.2] compounds. From the evidenced magnetization and magnetostriction results, the crucial finding that we emphasize is that the realization of minimum anisotropy for the compound with the composition x=0.1. From the X-ray diffraction on magnetically aligned samples, (440) peak splitting analysis and Mössbauer studies, we ascertain that the easy magnetization direction (EMD) for x=0.2 compound it is towards 〈110〉. Above results also affirmed that indeed there exists transformation of the structural distortion from rhombohedral to orthorhombic from x=0 to x=0.2. The Laves phase compound Tb0.3Dy0.6Nd0.1Fe1.93 with a large magnetostriction (λ111≈1270×10−6) and a low anisotropy may be a potential candidate for magnetostriction applications.

Large magnetostriction and direct experimental evidence for anisotropy compensation in Tb0.4−xNdxDy0.6(Fe0.8Co0.2)1.93 Laves compounds

Structure, spin configuration and magnetostriction of Tb0.4−xNdxDy0.6(Fe0.8Co0.2)1.93 (0≤x≤0.30) compounds are investigated. A single-phase Laves phase is synthesized at equilibrium conditions at ambient pressure for the indicated Nd-concentration range. Direct experimental evidence for magnetocrystalline-anisotropy compensation between Tb3+ and Nd3+ is obtained by performing X-ray diffraction on magnetic-field aligned powders and by evaluating the easy magnetization direction and the magnetostriction. A large polycrystalline saturation magnetostriction λS (~1170ppm) is observed for x=0.05, which can be attributed to the large magnetostriction coefficients λ111 (~1600ppm) and λ100 (~520ppm). The compound Tb0.35Nd0.05Dy0.6(Fe0.8Co0.2)1.93 with large magnetostriction and low anisotropy is found to be a good candidate material for magnetostriction applications.

Magnetic properties and specific heat data of R11Ni4In9 (R = Pr, Nd, Sm, Gd and Tb) compounds

Magnetic and thermal properties of R11Ni4In9 compounds (R=Pr, Nd, Sm, Gd and Tb) were investigated by means of magnetic and specific heat measurements. These compounds crystallize in orthorhombic Nd11Pd4In9-type crystal structure in which the rare earth atoms occupy five nonequivalent sublattices. For all these compounds except Gd11Ni4In9, the ground state at low temperature is antiferromagnetic. Except Pr11Ni4In9, in temperature dependence of the specific heat a two phase transitions are observed. For compounds with R=Nd and Tb with increasing of the external magnetic field and/or temperature the change to the ferrimagnetic state is observed. Sm11Ni4In9 is an antiferromagnet with small ferromagnetic component. The critical temperature of magnetic ordering does not fulfill the de Gennes scaling which indicates the influence of the crystal electric field in stabilizing the magnetic ordering.

Magnetocaloric effect near the second order ferromagnetic transition in superstructure R15Si9C compounds (R = Gd, Tb and Dy)

Large magnetocaloric effect (MCE) has been observed in R15Si9C (R=Gd, Tb and Dy) compounds which was studied by magnetization and zero field heat capacity measurements. Gd15Si9C, Tb15Si9C and Dy15Si9C undergo ferromagnetic transition below 170K, 130K and 70K respectively. The Arrott’s plot (M2 vs. H/M plot) of the magnetization data and the heat capacity measurement indicate the magnetic transition to be second order in nature. Among Gd, Tb and Dy compounds the maximum value of magnetic entropy change (ΔSM or MCE) and relative cooling power (RCP) for a magnetic field change of 0–70kOe are evaluated to be −12.9J/kgK and 413J/kg for Dy15Si9C, around 70K with no hysteresis loss. The isostructural Gd and Tb compounds also exhibit large values of MCE and RCP around their respectively magnetic transition region. The value of adiabatic temperature change is found to be 5.06K, 6.64K and 5.52K for Gd, Tb and Dy compounds respectively at TC for 0→70kOe of field change. The full-width at half-maximum approaches to 85K and 64K respectively for 70kOe of field change for Tb and Dy counterpart. Large reversible MCE and RCP values indicate that R15Si9C are promising materials for magnetic refrigeration in appropriate temperature regions.

Large magnetocaloric effects of RFeSi (R = Tb and Dy) compounds for magnetic refrigeration in nitrogen and natural gas liquefaction

Magnetic properties and magnetocaloric effect (MCE) of intermetallic RFeSi (R = Tb and Dy) compounds have been investigated systematically. The RFeSi compounds undergo a second-order magnetic transition from ferromagnetic to paramagnetic states with the variation of temperature. The Curie temperatures determined from magnetization measurements are 110 K and 70 K for TbFeSi and DyFeSi, respectively, which are quite close to the liquefaction temperatures of natural gas (111 K) and nitrogen (77 K). Both compounds exhibit nearly same large MCE around their respective ordering temperatures. For a low magnetic field change of 1 T, the maximum values of magnetic entropy change −ΔSM and adiabatic temperature change ΔTad are 5.3 J/kg K and 2.1 K for TbFeSi, 4.8 J/kg K and 1.7 K for DyFeSi, respectively. Furthermore, a composite material based on (Tb1−xDyx)FeSi compounds is designed theoretically by using a numerical method, and it exhibits a constant −ΔScom of ∼1.4 J/kg K for a field change of 1 T in the wide temperature range of 67–108 K, satisfying the requirement of Ericsson-cycle magnetic refrigeration over the liquefaction temperatures of nitrogen and natural gas.

Prediction Study of the Mechanical and Thermodynamic Properties of the $$\hbox {RBRh}_{3}$$ RBRh 3 (R $$=$$ = Sm, Eu, Gd, and Tb) Compounds

The structural, elastic, and thermodynamic properties of the cubic anti-perovskite $$\hbox {RBRh}_{3}$$ (R = Sm, Eu, Gd, and Tb) compounds have been investigated using first principles full-potential augmented-plane wave plus local orbitals (FP-APW+lo) method with the generalized gradient approximation. The ground-state quantities such as the lattice parameter, bulk modulus, and its pressure derivative, as well as elastic constants are estimated. Computed equilibrium lattice constants agree well with the available experimental data. The full set of first-order elastic constants and their pressure dependence, which have not been calculated or measured yet, have been determined. The elastic moduli increase linearly with increasing pressure and satisfy the generalized elastic stability criteria for cubic crystals under hydrostatic pressure. The shear modulus, Young’s modulus, and Poisson’s ratio are calculated for ideal polycrystalline $$\hbox {RBRh}_{3}$$ aggregates. The Debye temperature is estimated from the average sound velocity. From the elastic parameter behavior, it is inferred that cubic anti-perovskites $$\hbox {RBRh}_{3}$$ are ductile in nature and that the bonding is predominantly of an ionic nature. Following the quasi-harmonic Debye model, the temperature effect on the lattice constant, bulk modulus, heat capacity, and Debye temperature is calculated reflecting the anharmonic phonon effects.

Optimization on magnetic transitions and magnetostriction in TbxDyyNdz(Fe0.9Co0.1)1.93 compounds

The structure, magnetic transitions, and magnetostriction of TbxDyyNdz(Fe0.9Co0.1)1.93 polycrystalline compounds have been investigated, with the ratio of x, y, and z spanning the line of minimum magnetic anisotropy. Anisotropy compensation with lower Tb content was realized in Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 compound. The spin configuration diagram accompanied with different crystal structures was constructed to illustrate the arrangement for the easy magnetization direction and crystal structure. An optimized effect on magnetostriction especially at the relatively low field of 1 kOe (197 ppm) was observed in Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 compound, which is about two times larger than that of the sample free of Nd (62 ppm). Meanwhile, the polycrystalline saturation magnetostriction (λs=945 ppm) of Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 is even much larger than that of the Ho-doped multicomponent single crystal compound Tb0.2Dy0.22Ho0.58Fe2 (λs=530 ppm). Low content of heavy rare earth Tb, high Curie temperature, and large ratio between magnetostriction and the absolute value of the first anisotropy constant λa/|K1| were obtained in Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 compound, which may make it a potential material for magnetostrictive application.

Magnetostriction of TbxDy0.9−xNd0.1(Fe0.8Co0.2)1.93 compounds and their composites (0.20⩽x⩽0.60)

The structure, spin configuration, magnetocrystalline anisotropy compensation, magnetic properties, and magnetostriction of TbxDy0.9-xNd0.1(Fe0.8Co0.2)(1.93) (0.20 axis (x >= 0.25) to the axis (x >= 0.30) with increasing Tb content, subjected to the anisotropy compensation between Tb3+ and Dy3+ ions. The analysis of X-ray diffraction, EMD and magnetostriction show that TbxDy0.9-xNd0.1(Fe0.8Co0.2)(1.93) is an anisotropy compensation system and the compensation point is realized around x = 0.30. The Laves phase compound Tb0.4Dy0.5Nd0.1(Fe0.8Co0.2)(1.93) has a large spontaneous magnetostriction, the coefficient lambda(111) up to about 1640 ppm. The epoxy bonded 0-3 and pseudo-1-3 composites were fabricated by curing without and with a magnetic field. A high magnetostriction, longitudinal lambda(||) and linear anisotropic lambda(a)(=lambda(||)-lambda(perpendicular to)) up to around 390 and 650 ppm at 6 kOe, respectively, is obtained for the grain -oriented pseudo-1-3 epoxy/Tb0.4Dy0.5Nd0.1(Fe0.8Co0.2)(1.93) composite with 20 vol% alloy particles. (C) 2013 Elsevier B.V. All rights reserved.

Lanthanide coordination polymers constructed from 5-(4-pyridyl)-isophthalic acid: Synthesis, structure and photoluminescent properties

Abstract Nine lanthanide coordination polymers [Ln2(pyip)3(H2O)4·DMF·3H2O]n (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho) based on the pyip2 − ligand {H2pyip = 5-(4-pyridyl)-isophthalic acid} have been synthesized under solvothermal conditions. X-ray crystallographic studies reveal that 1–9 are isostructural and crystallize in the triclinic system, space group P21/c, and exhibit a 3D framework. Topological analysis reveals that the 3D framework can be simplified to a uninodal 6-connected pcu alpha-Po primitive cubic type structure. Meanwhile, the luminescent properties of these nine coordination polymers in the solid state are also investigated. Especially the Eu and Tb compounds show bright red and green luminescence with luminescence lifetimes of 0.39 and 0.80 ms, respectively.

Electrical resistivity, Curie temperature and band structure in Tb0.27Dy0.73(Fe1−xCox)2 intermetallics

Electrical resistivity studies performed in a wide temperature range across the complete Fe/Co substituted Tb0.27Dy0.73(Fe1−xCox)2 intermetallic series, with a borderline compound Tb0.27Dy0.73Fe2 known as Terfenol-D are presented. Parameters characterizing the dependence of resistivity on temperature, including the Debye temperature, are determined. Residual, phonon and magnetic contributions are separated from electrical resistivity. The magnetic contribution to electrical resistivity is applied to estimate Curie temperatures. Regions of weak and strong ferromagnetism of the transition metal sublattice are evidenced. The Curie temperature increases with x, approaches a maximum for x = 0.3 and reduces across the rest of the series. Some results of electronic band structure calculations using the Full-Potential Linearized Augmented Plane Waves (FLAPW) method are also presented. A distribution function for the densities of 3d states is introduced and a formula to estimate the band splitting energy is proposed. The obtained 3d and 4s band splitting energies for iron, cobalt and average for transition metal are presented. The Curie temperature across the Tb0.27Dy0.73(Fe1−xCox)2 system is described using a formula relating to both the FLAPW calculated magnetic moments and the statistical properties of the substituted transition metal sublattice.

Photoluminescent 3D Lanthanide–Organic Frameworks Based on 2,5-Dioxo-1,4-piperazinylbis(methylphosphonic) Acid Formed via in Situ Cyclodehydration of Glyphosates

Hydrothermal reactions of lanthanide nitrates with glyphosate have resulted three new isostructural 3D lanthanide-organic frameworks, Ln(NO3)(H2L) [Ln = Eu (1), Tb (2), Gd (3); H4L = 2,5-dioxo-1,4-piperazinylbis(methylphosphonic) acid], with good yields, where H4L as a new ligand was formed via in situ cyclodehydration of original ligand glyphosates during the hydrothermal reaction. The compounds were thoroughly characterized by IR, UV-vis, elemental analysis, single-crystal X-ray diffraction analysis, powder X-ray diffraction analysis, and thermogravimetric/differential thermal analysis (TG-DTA). Three compounds display 3D 6,6-connected open frameworks with 4(13)·6(2) topology possessing 1D channels in which NO3(-) anions act as troglodytes by chelating Ln(3+) centers. The TG-DTA study of the compounds showed remarkable thermal stability up to 380 °C. Under room temperature UV-light irradiation, the Eu(3+) and Tb(3+) compounds showed the corresponding characteristic Ln(3+) intra 4f(n) emission peaks. The triplet energy level (21882 cm(-1)) of the ligand (H4L) was determined from the emission spectrum of its Gd(3+) compound at 77 K. The emission lifetimes (1.54 ms of (5)D0 for compound 1 and 1.98 ms of (5)D4 for compound 2) and absolute emission quantum yields (10.1% for compound 1 and 5.9% for compound 2) were also determined.

A cluster-glass magnetic state in R5Pd2 (R = Ho, Tb) compounds evidenced by AC-susceptibility and neutron scattering measurements

AC- and DC-susceptibility, high-field magnetization and neutron diffraction measurements have been performed in order to study the magnetic state of R5Pd2 (R = Ho, Tb) compounds. The results show that both compounds undergo cluster-glass freezing upon cooling below Tf. According to the neutron diffraction a long-range magnetic order is absent down to 2 K and magnetic clusters with short-range incommensurate antiferromagnetic correlations exist not only below Tf but also in a wide temperature range above the freezing temperature (at least up to 2Tf). A complex cluster-glass magnetic state existing in Ho5Pd2 and Tb5Pd2 down to low temperatures results in rather complicated magnetization behavior in DC and AC magnetic fields. Such an unusual magnetic state in compounds with a high rare-earth concentration may be associated with the layered type of their crystal structure and with substantial atomic disorder, which results in frustrations in the magnetic subsystem.

Critical behaviour of the RCo3B2 (R = Gd, Tb and Dy) compounds

The critical properties of RCo3B2 (R=Gd, Tb, and Dy) compounds around the rare earth sublattice magnetic phase transition have been investigated by using the field dependence of magnetic entropy change method. The obtained values of critical exponents for all the compounds satisfied with the scaling theory. The critical behaviour of RCo3B2 compounds lies between mean-field model and 3D Heisenberg model, close to Tricritical mean-field model, and close to 3D Ising model for R=Gd, Tb, and Dy, respectively. The present results have confirmed that the field dependence of magnetic entropy change method can be applied to study the critical behaviour of magnetic materials.

Magnetocaloric effect in the rare earth intermetallic compounds RCoNi (R = Gd, Tb, Dy, and Ho)

Magnetic and magnetocaloric properties of cubic Laves phase RCoNi (R = Gd, Tb, Dy, and Ho) compounds have been studied. The RCoNi (R = Gd, Tb, Dy, and Ho) compounds order ferromagnetically at ∼200 K, ∼113 K, ∼68 K, and ∼42 K (TC), respectively. Field dependent magnetization data of RCoNi at 5 K in fields up to 7 T reveal saturation behaviour with minimal hysteresis. Magnetocaloric effect in terms of isothermal magnetic entropy change has been calculated. Maximum isothermal magnetic entropy change values of ∼−7.2 J/kg/K, ∼−10.1 J/kg/K, ∼−15.5 J/kg/K, and ∼−19.6 J/kg/K are obtained for RCoNi (R = Gd, Tb, Dy, and Ho) compounds for 7 T field change close to TC. Substitution of 50 at. % Ni in Co-site of RCo2 has led to the reduction of TC of the parent compounds by nearly one-half, but broadened the magnetic entropy change vs T curve and hence improved the relative cooling power. The large magnetocaloric effect associated with RCoNi compounds makes them potential candidates for low temperature magnetic refrigeration applications.

Magnetic Properties of RIrSi (R = Tb, Dy, and Ho) Compounds

The magnetic data for the polycrystalline samples of RIrSi (R = Tb, Dy and Ho) compounds are reported. These compounds are antiferromagnets with the Neel temperatures equal to 32 K (R = Tb), 7.0 K (R = Dy) and 4.8 K (R = Ho), respectively. The external magnetic eld induces the one step for TbIrSi and two step for DyIrSi and HoIrSi metamagnetic phase transitions. The values of the critical eld as Neel temperatures decrease with increase of the number of 4f electrons. The magnetic phase diagrams (H,T ) are determined.

Syntheses, structures, tunable emission and white light emitting Eu3+ and Tb3+ doped lanthanide metal–organic framework materials

A series of novel lanthanide metal-organic frameworks, namely, {[Ln2(L)2]·(H2O)3·(Me2NH2)2}n (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Ho (9), Er (10)), have been synthesized with hydro(solvo)thermal conditions based on a flexible multicarboxylic acid (H4L = 5-(3,5-dicarboxybenzyloxy)isophthalic acid). Single crystal X-ray diffraction reveals that all of them are isomorphous and possess a (6,6) topological net with a Schläfli symbol of {4(8)·6(7)}. Considering the blue-emission of compound 1 and the intense emission of the Eu and Tb compounds, we successfully construct isostructural Eu(3+) doped Tb compounds whose color can be tuned easily by adjusting the different concentration of the doped ions, and we also obtained white light emitting materials through the doping of Eu and Tb ions in the La compounds.

Effect of lanthanide contraction on crystal structures of Ln(iii) coordination polymers with dinuclear SBUs based on 3-(4-hydroxypyridinium-1-yl) phthalic acid and oxalic acid

A series of lanthanide coordination polymers, {[Ln(L)(OX)0.5(H2O)2]·3H2O}n (Ln = La 1, and Ce 2), [Ln2(L)2(OX)(H2O)3]n (Ln = Pr 3, Nd 4, Sm 5, Eu 6, Gd 7, Tb 8, Dy 9, Er 10, and Yb 11) (H2L = (3-(4-hydroxypyridinium-1-yl) phthalic acid, H2OX = oxalic acid), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. The title compounds are crystallized in the same triclinic space group P but display different 2D layer structures with different dinuclear secondary building units (SBUs) due to the effect of lanthanide contraction. Furthermore, X-ray diffraction and thermogravimetric analysis of 1–11 are also studied, which demonstrate their high purities and good thermal stabilities. Luminescent measurements indicate that the Eu (6), Tb (8), and Dy (9) compounds exhibit ligand (L2−) sensitized emissions in red, green, and yellow light regions, respectively.

Photoluminescence properties of PVP/Tb(TTA)2(Ph3PO)2NO3 nanocomposites

Thin films (1–10μm thickness) of nanocomposites (NCs) based on a coordinated compound (CC) Tb(TTA)2(Ph3PO)2NO3 (where TTA is thenoyltrifluoroacetonate (C8H5F3O2S), and Ph3PO is triphenylphosphine oxide) and a polymer — polyvinylpyrrolidone (PVP) ((C6H9NO)n) were obtained by chemical methods. NCs were characterized by measurements of optical transmission, and photoluminescence (PL) at different concentrations of CC in NCs. Using the optical transmission spectra, the characteristic parameters of NCs such as the threshold of absorbance versus the concentration of the CC in NCs were determined. A slight displacement of the absorption threshold to the infrared region was observed with increasing concentration of coordinated material in NCs. It was established that the excitation spectrum at which the photoluminescence (PL) in NCs takes place covers the range of wavelengths from 200 to 410nm. The PL of nanocomposites was detected as specific for internal transitions 4f→4f of the Tb3+ ion 5D4→7Fi (i=6, 5, 4 and 3) centred at 488, 543, 589 and 614nm, respectively at T=300K. The dominant PL was observed at 543nm and its half-width is less than 10nm. The intensity of the photoluminescence signal at 543nm in the case of the NC films is 2 times higher than the intensity of the PL of Tb(TTA)2(Ph3PO)2NO3 powders at equal conditions of excitation. The PL intensity of the NCs at 77K has grown more than 20 times compared with that at 300K.

Computational finding of potential inhibitor for Cytochrome P450 Mono-oxygenases Enzyme of Mycobacterium tuberculosis.

Cytochrome P450 mono-oxygenases (2UUQ) enzyme from Mycobacterium tuberculosis catalyzes oxidation of organic compounds such as lipids and steroidal hormones therefore remain as potential drug target. Currently available first line anti-tuberculosis drugs have been caused several side effects in the body as well as resistance development by mycobacterium against these drugs, necessitates the considerable need for finding new drugs. Therefore, we propose a structure based computational method to find a new potential inhibitor for cytochrome P450 mono-oxygenases enzyme. Compounds from several ligand databases were docked against the functional sites of 2UUQ (A) through the standard GEMDOCK v2.0 and AUTODOCK4.0 molecular docking tools. Commercially available chemical compound ZINC00004165 (5-[3-(2-nitroimidazol-1-yl) propyl] phenanthridine) has produced top rank with lowest interaction energy of -113.2 (via GEMDOCK) and lowest docking energy of -9.80 kcal/mol (via AUTODOCK) as compared to first line anti TB compounds. Z score and normal distribution analysis verified that the ZINC00004165 compound has more affinity towards 2UUQ in comparison to large number of random population of compounds. ZINC00004165 is also in agreement with the drug likeness properties of Lipinski rule of five without any violation. Therefore, our finding concludes that the commercial compound ZINC00004165 can act as a potential inhibitor against cytochrome P450 mono-oxygenases enzyme of Mycobacterium tuberculosis.