Tb Contents Research Articles

Structure-Activity Optimization of Luminescent Tb-doped LaF3 Nanoparticles.

A series of Tb-doped LaF3 nanoparticles (NPs) was prepared by systematically varying the Tb doping rate from 0 to 100%. The elemental composition was confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis, and the size, morphology, and crystal structure were determined in the solid state by transmission electron microscopy and X-ray diffractometry, while the size and ζ-potential of the NPs in solution were studied by dynamic light scattering, Taylor dispersion analysis, and laser Doppler electrophoresis. While the crystal structure appears to be hexagonal for a doping rate of up to 70%, an admixture of hexagonal and orthorhombic phases is observed for 80 and 90% Tb contents with a pure orthorhombic phase being obtained for TbF3. The spectroscopic properties of the NPs were studied for bare NPs and in the presence of dipicolinic acid as a surface-capping antenna ligand in solution. The coverage of the NPs by the ligand resulted in an increase in the luminescence lifetime of the emitting Tb centers, as a consequence of a better protection toward luminescence quenching from water molecules, as well as a large improvement in the brightness of the NPs. Taking into account the various parameters, a doping rate of 40% Tb was shown to be the best compromise for the development of such NPs for bioanalytical applications.

Analytical determination of tryptoquialanines A and B: Ensuring the quality and safety of orange juices

Although orange juice is a popular beverage worldwide, fruit distribution, storage, and processing can facilitate fungal infection by Penicillium digitatum; leading to the production of tremorgenic alkaloids, specifically tryptoquialanines A (TA) and B (TB). An Analytical method was developed and validated based on QuEChERS and LC-MS/MS analysis to determine the levels of TA and TB in fresh, industrial, and homemade orange juices. Excellent linearity was observed in the method over a high range of 1–1000 μg/kg and low range of 1–75 μg/kg with R2 ≥ 0.998. The LOD and LOQ were 1 and 3 μg/kg, respectively. Recoveries showed values between 57 and 83 %, with RSD ≤ 13 %. Our data indicated a higher prevalence of mycotoxin TA in fresh and industrial orange juices. Reduction in TA and TB content after thermal and HPP treatments were ≤ 32 %. However, thermal treatment was more effective in reducing TA and TB contents.

Scheelite trace element compositions: A robust new tool for mineral exploration

Scheelite is a widespread accessory tungstate mineral that contains a variety of trace elements. Scheelites from the major types of magmatic-hydrothermal mineral deposits (86 deposits, including quartz-vein and greisen, porphyry, skarn and orogenic Au deposits) have been collected and analyzed using laser ablation-inductively coupled plasma mass spectrometry (3270 data, including 584 analyses). Discriminant analysis using Mo, Sr, Nb, La, Ce, Eu, Dy, Yb, Y, Ta, Pb, (Ce/Yb)N, (La/Sm)N, (Gd/Yb)N, Eu anomaly, Ce anomaly, (La/Yb)N, LREE/HREE, Y/Ho and Mo + Sr + Nd + rare-earth elements (REE) + Y + Ta + Pb reveals that scheelites from different mineral deposits can be distinguished. Scheelites from quartz-vein and greisen deposits have high total contents of trace elements that partition onto the Ca sites (Mo, Sr, Nd, REE, Y, Ta, Pb). Scheelites from the porphyry W ± Cu ± Mo deposits, which have been studied in this work, are characterized by low Mo and positive Eu than scheelites from porphyry Cu ± Mo deposits. This indicates that large scale tungsten deposits are related to reduced hydrothermal fluids, in contrast to the oxidized fluids associated with porphyry Cu ± Mo deposits. Scheelites from skarn W ± Sn ± Mo deposits typically exhibit a wide range of Y/Ho ratio and a higher sum of the elements Mo, Sr, Nd, REE, Y, Ta, and Pb compared to that from the skarn Cu ± Mo ± W deposits, indicating that increased amount of fluorine probably leads to large-scale W, Mo, and Sn mineralization during magmatic-hydrothermal processes. Scheelites from the greisen W-Sn polymetallic deposits tend to have more restricted Sr compositions and Eu anomalies than those from the quartz vein W-Sn deposits, as well as relatively high Gd, Tb, Dy and Ho contents, which coincide with extensive hydrothermal alteration, indicating intense fluid-rock interaction during mineralization. Using Discriminant projection analysis (DPA), scheelites from many ore deposits can be readily separated from each other. This study demonstrates that heavy-mineral scheelite grains collected during regional geochemical surveys are effective in identifying specific types of buried mineral deposits in potential mineralization area. Scheelite geochemistry with DPA provides an effective guidance for mineral exploration.

Manipulating exchange bias in Ir25Mn75/CoTb bilayer through spin–orbit torque

Manipulation of exchange bias (EB) via spin-current-induced spin–orbit torque (SOT) is of great importance in developing full electric control spintronic devices. Here, we report on SOT-dominant manipulation of the interfacial antiferromagnetic spins and the related perpendicular EB (PEB) in the IrMn/Co1-xTbx (CoTb) bilayers with various Tb contents. No matter the magnetization of the ferrimagnetic CoTb layer is Co-dominant or Tb-dominant; all the samples were perpendicularly magnetized, and spontaneous PEB could be established during the isothermal crystallization of the IrMn layer. The SOT-induced EB switching could be accomplished with assistance of an in-plane or out-of-plane external magnetic field, associated with a monotonic reduction of the EB switching fraction by increasing x. This phenomenon is attributed to weakening of the interfacial exchange coupling between the CoTb and IrMn layers as x is increased. These findings provide a way to design high energy-efficient spintronic devices by employing the antiferromagnet/ferrimagnet bilayers, which may have weak stray field and strong robustness in contrast to commonly used heavy-metal/ferromagnet/antiferromagnet trilayers.

New grain boundary diffusion strategy of Nd-Fe-B sintered magnets to achieve breakthroughs in Tb-availability and thick limitation

Grain boundary diffusion (GBD) Nd-Fe-B sintered magnets were prepared using a newly developed solid-liquid phase separation diffusion (SepD) technique, as well as a currently popular solid-liquid phase simultaneous diffusion (SimD) technique. The magnetic properties, microstructures, and magnetic domain morphologies of the magnets with different Tb contents diffused using the two techniques were then investigated. A SepD magnet using 0.25 wt% Tb exhibited a similar coercivity and a stronger maximum energy product compared to a SimD magnet with 0.50 wt% Tb, demonstrating high Tb availability. Moreover, by using the new diffusion technique, Tb could diffuse deeper into the magnet and distribute more homogeneously around the surface region of the Nd2Fe14B crystal grains, forming the crucial core-shell structure without undesirable enrichment in the surface area of the magnet. As a result, the squareness factor increased noticeably from 0.842 for the current technique diffused magnet to 0.925 for the new technique diffused magnet with a thickness of 8 mm.

Multivariate statistical analysis of trace elements in apatite: Discrimination of apatite with different origins

Partial least squares-discriminant analysis (PLS-DA) was used to construct the link between trace element contents of magmatic or hydrothermal apatite and deposit and rock types. Apatite with different origins is discriminated by characteristic chemical composition. In average, ore magmatic apatite has higher light REE and Th, and lower Sr than barren rock apatite, independent of deposit types. Hydrothermal apatite has lower La, Ce, Pr, and Nd contents than magmatic apatite, probably because fluids prefer migrating light rare earth element out of apatite. Hydrothermal apatite from iron oxide copper gold (IOCG) and iron oxide apatite (IOA) deposits is discriminated by high Mn and Sr relative to magmatic apatite, probably because these elements are fluid mobile. Barren magmatic apatite from granitoid-related deposits is well separated from ore magmatic apatite by higher Sr, Eu, Gd, Tb, Dy, and lower Mn contents, which are likely related to the relatively low degree of differentiation and high aluminum saturation index of parental magma.Magmatic apatite from IOA deposits is discriminated by relatively high Nd, Sm, Gd, Tb, Dy, and low Mn and U contents, which are possibly related to the crystallization of Mn-compatible magnetite microlites and peraluminous magmas. Magmatic apatite from granitoid-related W deposits is relatively rich in Y, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The relative enrichment of Sr in magmatic apatite from granitoid-related Cu-Pb-Zn and Pb-Zn deposits is likely due to less fractionation of Sr-compatible plagioclase. Melt of sediment component accounts for high Mn and Th in magmatic apatite from granitoid-related Mo deposits. Magmatic apatite from porphyry deposits is discriminated by relatively high V, Sr, and Eu contents. Magmatic apatite from porphyry Mo deposits has relatively high Pr, Nd, and Sm and low Sr contents compared to other types of porphyry deposits due to the more evolved magma. Hydrothermal apatite from IOA deposits is discriminated by high V and Sr, whereas those from IOCG deposits have high Sm, Eu, Gd, Tb, and U contents, because the lower temperature of IOCG cause precipitation of REE in Cl-rich fluid. Relatively low Gd and Tb in hydrothermal apatite from skarn deposits are possibly due to the crystallization of amphibole.Apatite in carbonatite has high contents of trace elements possibly because high contents of Ca and P in melts cause high apatite-melt partition coefficients of trace elements. Apatite from sedimentary and metamorphic rocks is discriminated by relative enrichment of Sr and Eu. Compared to igneous rocks, apatite from sedimentary rocks has low REE contents, reflecting low REE budget in surface waters. Breakdown of some minerals to release and remobilize REE and U during metamorphism can interpret high heavy REE and U contents in apatite from high-grade metamorphic rocks relative to those from low- and medium-grade metamorphic rocks. The ability to discriminate apatite from different types of deposits and rocks indicates the application potential of apatite chemistry in mineral exploration. A flowchart was proposed to identify apatite with unknown origins.

Monitoring the Simultaneous Implantation of Ti and Tb Cations to a Sacrificial Template and the Sol-Gel Synthesis of Tb-Doped TiO2 (Anatase) Hollow Spheres and Their Transition to Rutile Phase

Tb-doped TiO2 (anatase) micro-hollow spheres (HSs) with nano-shells, in the range 0.00-3.00 at.% Tb, were successfully synthesized by a simultaneous chemical implantation route of both Ti and Tb cations from chlorides to a poly-styrene (PST)-co-poly-divinyl benzene (PDVB) sacrificial template, followed by controlled hydrolysis and polycondensation reactions. After water addition to the mixture of the precursors with the template, a decrease in the intensity and a shift to lower wavenumbers of the C=O absorption band in the IR spectra can indicate not only the anchoring of Ti and Tb ions to the carbonyl group of the template but also the hydrolysis of the implanted precursors. This latter process can involve a proton attack on the Ti-Cl, Tb-Cl and C=O bonds, the occupation of a vacant site by a water molecule, and then the dissociation of the dangling Ti-Cl, Tb-Cl ligands and C=O bonds. It gives rise to Ti1-xTbx[(OH)4-uClv]@PST-PDVB and Ti1-xTbx[(OH)4-y]@PST-PDVB complexes (x = 0.00, 0.0012, 0.0170 and 0.030). Finally, polycondensation of these species leads to Ti1-xTbxO2-w'@PST-PDVB compounds. After subsequent thermal removal at 550 °C of the template, the IR bands of the core (template) totally vanished and new bands were observed in the 400-900 cm-1 region which can be attributed to the metalloxane bondings (M-O, M'-O, M-O-M, M-O-M' and/or M'-O-M', being M and M' = Ti and Tb, respectively, i.e., mainly vibration modes of anatase). Then, micron-sized HSs of TiO2 and Tb-doped-TiO2 (anatase) were obtained with nano-shells according to field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM) observations. Furthermore, X-ray photoelectron spectroscopy (XPS) measurements confirmed the presence of Tb4+ (38.5 and 41.2% for 1.70 and 3.00 at.% Tb, respectively) in addition to Tb3+ in the resulting HSs, with increasing Tb4+ content with both Tb doping and higher calcination temperatures. Then, these HSs can be considered as rare earth (RE) co-doped systems, at least for 1.70 and 3.00 at.% Tb contents being the transition to rutile phase favored by Tb doping for those compositions. Finally, diffusion of Tb from the inner parts to the surface of the HSs with the calcination treatments was also observed by XPS.

Reducing the process consumption of Tb in grain boundary diffusion of Nd-Fe-B magnets by sputtering deposition instead of adhesive coating

Grain boundary diffusion (GBD) can enhance the coercivity of Nd-Fe-B magnets with relatively low consumption of heavy rare earths (HREs). Most of previous investigations on GBD focused on improving the efficiency of diffusion source, but less attention has been paid on reducing the process consumption of HRE. Here, a comparative study on coating methods of adhesive coating and sputtering deposition is carried out to evaluate the surface state of diffused magnet and the process consumption of HRE during surface cleaning. The results suggest that 0.9 wt.% sputtering deposited Tb-Cu alloy can enhance the coercivity of the magnet from 1053 kA/m to 1668 kA/m, due to the formation of high-anisotropy (Nd,Tb)2Fe14B phase and the optimized intergranular phases. To obtain smooth magnet surface for the subsequent surface protection process, the surface of the diffused magnet is polished, which leads to the reductions of magnet thickness and coercivity of ∼40 µm and 25 kA/m, respectively. In comparison, when 0.9 wt.% Tb-Cu source was coated by adhesive coating, although a comparable coercivity of 1663 kA/m can be obtained, the as-diffused magnet shows a rough surface and the polishing process leads to the reductions of magnet thickness and coercivity of ∼140 µm and 81 kA/m, respectively. By fitting the concentration-depth curves based on Fick’s second law, Tb contents in the diffused magnets decrease by 74 % and 13 % after surface cleaning for adhesive coating and sputtering deposition processes, respectively. The results suggest that the process consumption of Tb in GBD of Nd-Fe-B magnets can be greatly saved by sputter deposition.

Noticeable enhancement in NH3 sensing performance of nebulizer spray pyrolysis deposited SnO2 thin films: An effect of Tb doping

Rare metal Terbium (Tb) doped SnO 2 (SnO 2 :Tb) films were fabricated via spray pyrolyzed method with different doping concentrations. The effects of terbium doping concentration on its microstructural, optical, photoluminescence , and room temperature ammonia vapor sensing properties were reported. The crystallite size of the prepared Tb-doped tin oxide films decreases with an increase in doping concentrations. The obtained crystallite size ranges from ~ 12 – 9 nm. The terbium incorporation was confirmed by EDS and elemental mapping. The bandgap values are enhanced as the concentration of Tb doping increases. The high gas response of 79% with fast response/recovery of 31/11 s , respectively is reported for 25 ppm of ammonia at room temperature for 5% Tb doped sample. The gas sensing cycle test shows the excellent sensitive behavior of the films without any decrease upon 5 repeated cycles. The stability of the sample was also checked for a corresponding Tb 5% doped sample, which revealed a stable response even for 50 days. • Novel SnO 2 :Tb thin films were fabricated facilely by nebulizer spray pyrolysis technique. • XRD study confirm monophasic rutile tetragonal films fabrication at all Tb contents. • Energy gap was enhanced from 3.63 to 3.76 eV on Tb doping in SnO 2 . • The highest response/quick recovery time of 31s/11s was noticed for 5 wt% SnO 2 :Tb films at 300K. • The stability of 5 wt% SnO 2 :Tb film was tested and noticed a stable response even for 50 days.

Photoluminescence changes of Tb-substituted layered double hydroxides caused by capturing carbonate ions in water

Tb-substituted layered double hydroxides (Tb-LDHs) with NO3− in the interlayer were synthesized by a hydrothermal method and then used to capture and sense CO32− in aqueous solution. X-ray diffractometry confirmed that single-phase Tb-LDHs with Tb contents of 1–5 mol% were successfully synthesized. The NO3− ions of 5 mol% Tb-substituted LDH (Tb5LDH) were exchanged by CO32− ions in a Na2CO3 aqueous solution at pH = 11. The ion exchange for Tb5LDH was promoted with increasing the concentration of the Na2CO3 solution. Photoluminescence spectroscopy revealed that Tb5LDH with CO32− in the interlayer displayed an excitation wavelength of 229 nm and exhibited a green emission signal originating from the 4f8 → 4f75d1 transition, 5D4 → 7FJ (J = 3, 4, 5, 6), in the range of 400–700 nm. The intensity of the emission signal of the ion-exchanged Tb5LDH excited at 229 nm increased with increasing the content of CO32− in Tb5LDH. These results indicate that Tb5LDH was capable of capturing and sensing CO32− dissolved in water by irradiation with 229-nm light.

Boundary structure modification and coercivity enhancement of the Nd-Fe-B magnets with TbCu doping by the process of pre-sintering and hot-pressing

The high-coercivity Nd-Fe-B magnets with “core-shell” structure grains were prepared by doping TbCu powders and hot pressing after pre-sintering in the traditional powder metallurgy process. The coercivity for the hot-pressed pretreated Nd-Fe-B magnet is obviously enhanced to 28.6 kOe from 24.3 kOe by TbCu alloy doping. The Tb contents at the shell structure of grain in the hot-pressed pretreated magnet is 5.7 wt% while that in the dual-alloy magnet is 3.0 wt%. The enrichment of Tb elements in the shell layer further enhances the anisotropy of the grain surface and effectively improves the utilization efficiency of heavy rare earths. The existence of the hard (Tb, Nd)2Fe14B shell, which can effectively inhibit the reverse nucleation of magnetic domains, contribute to enhance the coercivity with few reduction of the remanence. Compared with the grain boundary diffusion process, this technology can be used to prepare large pieces of high performance Nd-Fe-B bulk magnets without diffusion depth limit.

The Spatiotemporal Distribution of Two Bacterial Indexes in a Small Tibetan Plateau Watershed

Microbial contamination is now more common than chemical contamination in Tibet, and water-borne microbes can cause a number of diseases that threaten public health. Thus, in order to clarify the spatiotemporal distribution of bacteria in small watersheds for which there is no data in Tibet, four sampling points were set up along an upstream-downstream transect of the Xincang River Basin. A total of 239 water samples were collected in 2014 and 2015, and their total constituent numbers of bacteria (TB) and coliforms (TC) were evaluated. The results of this study show that the microbial contamination of the Xincang River Basin is mild-to-moderate in terms of TB and TC contents, and that these concentrations vary significantly in different seasons. The results show that in summer, TB and TC concentrations and microbial contamination are almost at the same level in upstream, midstream, and downstream sections; however, in the other three seasons, microbial contamination in the downstream section is more serious than in the upstream and midstream sections. The data also demonstrates that concentrated precipitation and local contamination sources are important factors underlying increases in TB and TC concentrations during the summer months. The results of this study are likely to reflect the basic characteristics of small watersheds for which there is no data to some extent, and are thus of significant practical importance for protecting their ecological environments and promoting sustainable development.

Photoluminescence, scintillation and thermally-stimulated luminescence properties of Tb-doped 12CaO·7Al2O3 single crystals grown by FZ method

Tb-doped 12CaO·7Al2O3(Tb:C12A7) crystals were synthesized by the floating zone (FZ) method and the photoluminescence (PL), scintillation and thermally-stimulated luminescence (TSL) properties were investigated. The photoluminescence (PL) emission spectra and PL decay time profiles were investigated by using Quantaurus-tau (Hamamatsu). The scintillation spectra and decay time profiles were measured by using our laboratory-constructed set-up under X-ray irradiation. Finally, TSL glow curve was measured by using Nanogray TL-2000 with the heating rate of 1 °C/s. In PL and scintillation, emission peaks were observed at 493, 543, 587 and 620 nm due to the 4f-4f transitions of Tb3+. Decay time constants of the emission by PL and scintillation appeared to be different, and the measured values were approximately 2.4 and 1.9 ms, respectively. After X-ray irradiations, the 0.5% (all Tb contents in this paper are in mole fraction) and 1.0% Tb-doped samples showed a single intense and broad glow peak around 100 °C while 1.2%−1.5% Tb-doped samples showed notable additional peak around 250 °C.

Methylxanthine and catechin content of fresh and fermented cocoa beans, dried cocoa beans, and cocoa liquor

The theobromine and catechin content can affect the quality of cocoa liquor and is influenced by cacao variety, production area (PA), and fermentation, as well as the method of drying beans (FDB) and cocoa liquor production (CLP). This study examined variations in methylxanthine and catechin levels in fresh and fermented cocoa beans, dried cocoa grains, and in cocoa liquor from Trinitario, Criollo, and Forastero cacao varieties. A total of 123 cocoa bean samples from three Peruvian PAs at different altitudes, Tingo Maria (TM), San Alejandro (SA), and Curimana (CU), were evaluated. The theobromine (Tb) and caffeine (Cf) contents in fresh cocoa beans were affected by both cocoa type and PA. The caffeine content was higher in Trinitario cacao than in Criollo and Forastero varieties (p ≤ 0.05). The Tb and CF contents decreased in dry cocoa grain and was affected by FDB (p ≤ 0.05) (1.449 ± 0.004 to 1.140 ± 0.010 and 0.410 ± 0.03 to 0.165 ± 0.02 g Tb and C, respectively, per 100 g dry weight). Cocoa beans from Tingo Maria, which has the highest altitude, had higher Tb and CF contents than those from other PAs. The catechin (C) and epicatechin (EC) contents were affected by the FDB and CLP, and were highest in fresh cocoa beans from the Tingo Maria area (range: 0.065 ± 0.01 to 0.020 ± 0.00 g C/100 g). The C and EC contents decreased during FDB and CLP (0.001 g C/100 g of cocoa liquor). Taken together, these results show that higher concentrations of Tb, Cf, C, and EC are present in fresh cocoa beans. Moreover, the cocoa variety influenced cocoa liquor quality. Overall, cocoa from the Tingo Maria PA had the most desirable chemical composition.

Crystal growth of Sm0.3Tb0.7FeO3 and spin reorientation transition in Sm1−xTbxFeO3 orthoferrite

In this work, Sm0.3Tb0.7FeO3 single crystal was successfully grown by optical floating zone method. Sm0.3Tb0.7FeO3 samples with a-, b-, and c-orientation were manufactured by means of Laue photograph. Magnetic properties of Sm0.3Tb0.7FeO3 single crystals are studied over a wide temperature range from 2 to 400K. Spin reorientation transition from Γ2 to Γ4 are observed by means of the temperature dependence of magnetization It indicated the reorientation transition temperature of Sm1−xTbxFeO3 single crystals is lowered with the contents of Tb contents rising based on this work and our previous works, thus the spin reorientation transition temperature can be adjusted through changing the compound in orthoferrites materials, which means that we can get orthoferrites single crystals with high magnetism property in various temperature through material design.

Photoluminescence properties and energy transfer of color tunable MgZn2(PO4)2:Ce3+,Tb3+ phosphors

A series of Ce(3+)/Tb(3+) co-doped MgZn2(PO4)2 phosphors have been synthesized by the co-precipitation method. Their structure, morphology, photoluminescence properties, decay lifetime, thermal stability and luminous efficiency were investigated. The possible energy transfer mechanism was proposed based on the experimental results and detailed luminescence spectra and decay curves of the phosphors. The critical distance between Ce(3+) and Tb(3+) ions was calculated by both the concentration quenching method and the spectral overlap method. The energy transfer mechanism from the Ce(3+) to Tb(3+) ion was determined to be dipole-quadrupole interaction, and the energy transfer efficiency was 85%. By utilizing the principle of energy transfer and appropriate tuning of Ce(3+)/Tb(3+) contents, the emission color of the obtained phosphors can be tuned from blue to green light. The MgZn2(PO4)2:Ce(3+),Tb(3+) phosphor is proved to be a promising UV-convertible material capable of green light emitting in UV-LEDs due to its excellent thermal stability and luminescence properties.

Luminescence properties of Ca2 Ga2 SiO7 :RE phosphors for UV white-light-emitting diodes.

A series of Eu(2+) -, Ce(3+) -, and Tb(3+) -doped Ca2 Ga2 SiO7 phosphors is synthesized by using a high-temperature solid-state reaction. The powder X-ray diffraction and structure refinement data indicate that our prepared phosphors are single phased and the phosphor crystalizes in a tetrahedral system with the ${P\bar 42m}$ (113) space group. The Eu(2+) - and Ce(3+) -doped phosphors both have broad excitation bands, which match well with the UV light-emitting diodes chips. Under irradiation of λ=350 nm, Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) have green and blue emissions, respectively. Luminescence of Ca2 Ga2 SiO7 :Tb(3+) , Li(+) phosphor varies with the different Tb(3+) contents. The thermal stability and energy-migration mechanism of Ca2 Ga2 SiO7 :Eu(2+) are also studied. The investigation results indicate that the prepared Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) samples show potential as green and blue phosphors, respectively, for UV-excited white-light-emitting diodes.

Impacts of Tb substitution at cobalt site on structural, morphological and magnetic properties of cobalt ferrites synthesized via double sintering method

Cobalt ferrites substituted with terbium (Tb) at cobalt (Co) and iron sites were fabricated by double sintering method and were characterized by the XRD, fourier transform infrared (FTIR) spectroscopy, scanning electron microscope and hysteresis loops measurements. The XRD analyses confirm the formation of single spinel phase for x=0.0 and thereafter a small peak of secondary phase occurred. The lattice parameter was found to increase by increasing Tb contents and this was attributed to the larger ionic radius of Tb ions as compared to Co ions. FTIR revealed two absorption bands which are characteristic feature of spinel ferrites. The morphology studies exhibit the inhomogeneous grain size distribution. The saturation magnetization was found to exist in the range of 63–67emu/g and coercivity in the range of 405–435 Oe. The observed variation in saturation magnetization was attributed to the redistribution of cations due to the substitution of terbium at cobalt sites. The incorporation of terbium in cobalt ferrites substantially decreased the coercivity and remanence. The smaller values of coercive field suggest that these materials are potential candidates to be useful in high density data storage devices.

Magnetic, ferromagnetic resonance and electrical transport study of Ni1−xTbxFe2O4 spinel ferrites

The impacts of terbium (Tb) contents on magnetic, ferromagnetic resonance (FMR), electrical and dielectric properties of Ni1−xTbxFe2O4 ferrites were investigated. A vibrating sample magnetometer was employed to probe the magnetic properties of the samples at room temperature. It was found that with the increased terbium content, the coercive force and saturation magnetization were decreased which may be attributed to spin canting. Magnetic dynamics of the samples were studied by ferromagnetic resonance in X band (9.5GHz) at room temperature. The incorporation of terbium sufficiently lowers the FMR line-width. The decrease in FMR line-width is attributed to the reduction of super-exchange interactions. The DC electrical resistivity and activation energy are higher for the substituted samples. The dielectric constant, dielectric loss (tanδ) and AC-conductivity decreased on account of doping. The decrease in dielectric constant is imputed to the reduction in the internal viscosity of the doped samples. The dielectric data are explained on the basis of space charge polarization. As Ni–Tb ferrites have low value of coercivity, high dielectric constant and low tanδ, they may be attractive for application in switching and memory storage devices.

Correlation Between Ultrafast Demagnetization Process and Gilbert Damping in Amorphous TbFeCo Films

Ultrafast spin dynamics in Tbx(FeCo)1-x films is studied using the time-resolved magneto-optical Kerr effect. At pump fluence of 1.0 mJ/cm2 the ultrafast demagnetization processes are accomplished by one-step and two-step decays (the first fast and second slow decays) for low and high Tb contents, respectively. For the low Tb contents (x <; 0.08), the demagnetization time is almost a constant (~ 600 fs), which is similar with the demagnetization time (τ1) of the first fast decay for the high Tb contents due to bleaching effect. However, the following slow demagnetization time (τ2) for the high Tb contents strongly depends on the Tb contents. It increases with increasing Tb contents, and reaches a maximum of 3.0 ps at x=0.21, then decreases with Tb content further increasing. The distinguished slow decay process is suggested to ascribe to the Gilbert damping factor.