Dy Doping Research Articles

Temperature dependent magnetic properties of Dy-doped Fe16N2: Potential rare-earth-lean permanent magnet

Using the full potential linearized augmented plane wave method, we explored the magnetocrystalline anisotropy of Dy impurity doped α″-Fe16N2. Here, we considered two different Dy concentrations (1.56 and 3.125%). We also investigated the temperature dependence of the magnetic properties. The Dy site occupancy was found to be concentration dependent. The magnetic moments of Fe atoms near the Dy impurity was suppressed. However, we found a large magnetic moment in Dy atom (4.85–4.87 μB). Compared with the magnetic anisotropy constant in the pristine α″-Fe16N2 (0.57 MJ/m3), we obtained an enhanced perpendicular magnetic anisotropy. The calculated anisotropy constants in 1.56% Dy doping was 0.97 MJ/m3 while it became 1.27 MJ/m3 in 3.125% Dy doping. The Curie temperature in the pristine structure was about 820 K and it was suppressed to 765 K and 605 K in 1.56% and 3.125% Dy doping. At room temperature (300 K), the coercive field of 3.125% Dy doped system was enhanced almost 50% compared with that of the pure Fe16N2. We also found a maximum energy product of 50.9 MGOe for 3.125% Dy doping at 300 K. Our finding may suggest that the α″-Fe16N2 can be a potential permanent magnet with a lean Dy doping.

A synergetic approach of band gap engineering and reduced lattice thermal conductivity for the enhanced thermoelectric property in Dy ion doped ZnO

Donor cation substituted ZnO demonstrate a promising performance for the green energy harvesting and conservation. In this work we report the marked improvement in the thermoelectric transport properties of rare earth Dy ion substituted ZnO to achieve a maximum figure of merit ZT as 0.11 at 923 K for the 0.1 atomic% of Dysprosium doping. The enhancement in the TE properties were mainly through the increase in carrier concentration and by the energy filtering of carriers at the potential barrier formed in the lattice by Dy doping, which has a large atomic size and localized magnetic moment due to the presence of unpaired electrons. With the substitution of Dy3+ ion, excess electrons were generated in the conduction band of ZnO lattice and they were free to move hence to contribute for the upliftment of Fermi level towards the conduction band with an increment in the effective electron mass. Introduction of donor ion causes distortion of lattice structure and the induced strain responsible for the reduction of lattice thermal conductivity.

A supramolecular chain of dimeric Dy single molecule magnets decorated with azobenzene ligands.

We report the synthesis, ab initio calculations, magnetic and optical characterization of a DyIII-based dimeric compound named DyAZO. The dimers self-organize into a supramolecular chain decorated with photo-isomerizable azobenzene ligands. DyAZO displays single-molecule magnet (SMM) behavior. However, ab initio calculations highlight a quite strong admixture of MJ states of the 6H15/2 level of DyIII ions, the presence of low-lying excited MJ states and antiferromagnetic Dy-Dy dipolar coupling. This favors zero-field fast tunneling. Accordingly the Dy-doped analogue YDyAZO (5.5% Dy doping) displays enhanced magnetic relaxation with a hysteresis that is observed at 0.5 K. The influence of the cis- to trans-isomerization of the decorating azobenzene ligand on magnetic properties has been tested for both solid samples and solutions of DyAZO and YDyAZO. This provides hints for the synthesis of future Dy-based photo-isomerizable molecules.

Direct observation of spin diffusion enhanced nonadiabatic spin torque effects in rare-earth-doped permalloy

The relation between the nonadiabaticity parameter $\ensuremath{\beta}$ and the damping parameter $\ensuremath{\alpha}$ is investigated in permalloy-based microdisks. In order to determine $\ensuremath{\beta}$, high-resolution imaging of the current-induced vortex-core displacement is performed using scanning electron microscopy with polarization analysis. The materials properties of the films are varied via rare-earth Dy doping, leading to a greatly enhanced damping, while retaining the same spin configuration for the confined vortex state. A clear trend to much higher nonadiabaticity values is seen for the higher doping levels and an averaged value of $\ensuremath{\beta}=(0.29\ifmmode\pm\else\textpm\fi{}0.15)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ is determined for $1.73%$ Dy doping, compared to $(0.067\ifmmode\pm\else\textpm\fi{}0.014)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ which is extracted for pure permalloy. This is supportive of a similar scaling of $\ensuremath{\beta}$ and $\ensuremath{\alpha}$ in this system, pointing to a common origin of the spin relaxation which is at the heart of nonadiabatic transport and the dissipation of angular momentum that provides damping, in line with theoretical calculations.

Temperature dependence of the band gap of high optical quality CdS:Dy thin films based on exciton spectra

CdS:Dy films were prepared by CSVS method on the cleaned glass substrates. The influence of Dy doping on the optical properties of CdS thin (500 nm) films was studied. The presence of narrow lines of bound and free excitons in the photoluminescence, reflection and absorption spectra shows a remarkable optical quality of the investigated films. The temperature dependence of the band gap of the films was studied on the basis of measurements of the energy position of the free excitons. A decrease in the anisotropic crystal field and the effect of depolarization of free exciton absorption spectra with increasing temperature are observed. It was concluded that the efficiency of CdS:Dy thin films photovoltaic applications can be further increased.

Ferroelectric, dielectric properties and electrical conduction mechanism of epitaxial B1-xDyxFeO3 (x = 0.05, 0.075, 0.1, 0.125) thin films prepared by pulsed laser deposition

We report that Dy doping can be used to enhance ferroelectric properties and reduce leakage current in (001) epitaxial Bi1-xDyxFeO3 (BDxFO) thin films where x = 0.05, 0.075, 0.1, 0.125. The 120 nm thin BDxFO films were prepared by pulsed laser deposition (PLD). Saturated ferroelectric hysteresis (P-E) loops were observed at room temperature with an increase in remanent polarization (Pr) with the increase in applied electric field and Dy concentration. The improved Pr in BDxFO films from x = 0.05 to 0.1 is attributed to reduction in oxygen vacancies with an increase in Dy content that prevents electric domain back-switching. However, BDxFO (x = 0.125) film exhibit leaky and unsaturated loop which may be due to the appearance of microscopic defects in the film. The leakage current in BDxFO films decreased by an order of magnitude as Dy content increased from x = 0.05 to 0.1. The detailed leakage current mechanism analysis is also presented. The results of positive up negative down (PUND) method confirmed that intrinsic polarization is due to ferroelectricity and not due to leakage. Relative permittivity (ɛ') of BDxFO films increased whereas dielectric loss tangent (tan δ) reduced as Dy content increased from x = 0.05 to 0.1.

Effect of Dy substitution on the Structural and Gas sensing Properties of BiFeO3

Facile synthesis of Dy substituted BiFeO3 were employed using Glycine combustion method. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were employed to characterize the structure and morphology of the material. The effect of Dy doping on the crystalline structure, morphologies and gas sensing properties of the final products have been investigated. The gas sensing properties of Bi1−xDyx FeO3 (x = 0.00, 0.05) materials for semiconductor gas sensors are presented. For composition with x=0.05, sensor exhibited highest response (87%) towards acetone vapor at an operating temperature 250°C. The response and recovery time of the sensor for x = 0.05 were quite low (5sec and 40sec) respectively.

Luminescent characterization of rare earth Dy3+ ion doped TiO2 prepared by simple chemical co-precipitation method

Pure and rare-earth ion (Dy3+) doped TiO2 nanomaterials were prepared through a chemical co-precipitation method. The chemical composition, microstructure and optical properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy and photoluminescence (PL). XPS analysis reveals that Dy3+ ions are preferentially occupied in the TiO2 crystallite lattices. Both the XRD and TEM analyses confirm that both the pure and Dy doped TiO2 are in pure anatase phase and in nano size range, respectively. Also it is found that the maximum solubility limit for Dy3+ ions is found to be 0.4% in TiO2 matrix, above which it occupies interstitials and/or crystallite surface of TiO2 nanocrystals. From the UV-Vis spectroscopy studies it is found that Dy doping induces blue shift in TiO2. From the PL analysis it is found that doping Dy3+ improves the luminescence behavior in comparison with the pure TiO2 nanoparticles. Overall, doping very low concentrations of Dy3+ greatly alters the structural morphology and directly increases the luminescence behavior of TiO2 suitable for advanced optoelectronic applications.

Influence of Dy doping on key linear, nonlinear and optical limiting characteristics of SnO2 films for optoelectronic and laser applications

In the present work, pure and dysprosium (Dy) doped SnO2 films have been fabricated through sol-gel spin coating technique. Strong influence of Dy doping is observed on structural, morphological, vibrational, linear and nonlinear optical properties of SnO2 films. X-ray diffraction study revealed that deposited films exhibit tetragonal crystal structure with preferentially grown along (2 0 0) plane. With increase of doping concentration in SnO2, the crystallite size decreases while dislocation density and lattice distortion ratio increases. The characteristics Raman peaks of doped SnO2 thin films broaden, shifted and intensity decreases as compared to pure film which confirm the bonding between Dy and SnO2. Optical study shows that the prepared thin films are highly transparent and absorption increases with doping concentrations owing to increase of defects states. It is also observed that the optical band gap first increases and then lessens with rise of Dy-doping concentration which attributed to the Burstein-Moss (BM) effect. Additionally, dielectric constant and refractive index first decreasing with small doping concentration (1–3%) due to increase of carrier concentration, and then increases for higher doping (5–7%) due to increase of defect in SnO2 lattice. The values χ3 and β obtained by Z-scan measurement are observed in range of 0.31 × 10−7 to 1.28 × 10−7 and 1.27 to 5.32 × 10−4 cm W−1, respectively. The limiting threshold of pure and Dy doped SnO2 nanostructured films were calculated to be in the range of 5.37–11.18 kJ/cm2.

A computational and spectroscopic study of Dy3+ doped BaAl2O4 phosphors

Computational and experimental methods are employed to study the optical properties of Dy-doped BaAl2O4 matrix. Atomistic modelling is used to make predictions of Dy doping sites and charge compensation schemes. The symmetry predicts from atomistic modeling was used to calculate crystal field parameters and to obtain the energies of the electronic transitions of the Dy3+ ion. Dy-doped BaAl2O4 was prepared via a sol-gel proteic technique. The optical properties were studied using X-ray excited optical luminescence (XEOL) measurements. The X-ray absorption near-edge structure (XANES) at the Ba and Eu LIII-edges exhibits typical absorption spectra. The area under the XEOL spectra increases as the photon energy increases in the region around the Ba and Dy LIII-edges. The XEOL spectra showed typical Dy lines. Experimental and calculated values for the transition energies are compared. Computational and experimental methods are employed to study of Dy-doped BaAl2O4 matrix. Atomistic modelling is used to make predictions of Dy doping sites. The optical properties were studied using XEOL measurements.

The search for defects in undoped SrAl2O4 material

SrAl2O4:Eu,Dy is a very efficient long afterglow phosphor with wide range of possible applications. The luminescence properties and the possible luminescence mechanism of this material have been studied extensively, but there is almost no information available about the undoped material. Therefore, this article deals with the luminescence and thermally stimulated luminescence of an undoped SrAl2O4, revealing the possible defects that might be involved in the creation of the long afterglow in doped material. We conclude that undoped material exhibits some luminescence under X-ray irradiation in low temperature; close to room temperatures luminescence is almost fully thermally quenched in comparison to low temperatures. We can observe F and F2 center luminescence as well as trace metal luminescence in the emission spectrum. TSL glow curve yields the peaks that are close to those observed in material with Eu and Dy doping; therefore these peaks are clearly related to intrinsic defects. The peak at around 400 K, that is shifting with rare earth doping, might be due to dopant interaction with intrinsic defects.

Role of Dysprosium Doping on Structural, Optical, Magnetic and Electrical Properties of ZnO Nanorods

Well-defined Dy-doped ZnO rods were synthesized by hydrothermal route. Various studies were carried out on the synthesized rods like x-ray diffraction to confirm their hexagonal wurtzite structure; TEM, HRTEM and selected area electron diffraction to establish their rodlike structure; energy-dispersive x-ray spectroscopy analysis confirming appropriate substitution of dopant; UV-Vis spectra, which showed decrease in band gap with dopant concentration and photoluminescence study furnishing information regarding the presence of various types of defects. Further, magnetic studies were done using VSM to confirm roomtemperature ferromagnetic behaviour of both for undoped and doped ZnO rods and, the electrical studies were performed using four probe method, which confirmed that the ‘variation in resistivity with dopant concentration’ was related to crystallinity of the samples. UV-Vis spectra showed effect of dopant concentration on band gap and photoluminescence study confirms induced ferromagnetic behaviour due to Dy doping.

(Fe1-xDyx)3C/C composites: structure, magnetism and electrocatalytic properties for hydrogen evolution reaction

The (Fe1-xDyx)3C@C composites were produced by a simple sol-gel route. The structure, composition, morphology and magnetism of the composites are studied by many characterization methods, for example, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy (SEM, TEM) as well as vibrating sample magnetometer (VSM). Analysis of the above results indicates that the (Fe1-xDyx)3C is embedded in carbon nanotubes and carbon matrix and displays ferromagnetic properties. Moreover, this indicates that saturation magnetization (MS) values of the composites tend to increase with the increase in Dy doping. More importantly, we investigates the electrochemical hydrogen production capacity of the (Fe1-xDyx)3C@C composites.

Ultrafast electron-phonon coupling and photo-induced strain in the morphotropic phase boundary of BixDy1\u2212xFeO3 films

The interplay among ferroelectric, magnetic and elastic degrees of freedom in multiferroics is the key issues in condensed matters, which has been widely investigated by various methods. Here, using ultrafast two-color pump-probe spectroscopy, the picosecond electron-phonon and spin-lattice coupling process in Dysprosium doped-BiFeO3 (BDFO) films on SrTiO3 (STO) substrate have been investigated systematically. The Dy-doping induced structural transition and magnetic enhancement in BDFO is observed by ultrafast electron-phonon and spin-lattice interaction, respectively. The elastic anomalies in BDFO films are revealed by the photo-induced coherent acoustic phonon. With increasing the Dy doping ratio, the frequencies of the acoustic phonon in the films are modulated, and the phonon transmission coefficient between films and substrate is found to approach unity gradually. The ultrafast observation of the tunability of the ferroelectric, magnetic and the elastic properties in the morphotropic phase boundary of rare-earth doped BFO films provides new insights into the integration of BFO in next-generation high frequency electro-magnetic and electroacoustic devices.

Enhanced ultraviolet photo-response in Dy doped ZnO thin film

In the present work, a Dy doped ZnO thin film deposited by the spin coating method has been studied for its potential application in a ZnO based UV detector. The investigations on the structural property and surface morphology of the thin film ensure that the prepared samples are crystalline and exhibit a hexagonal crystal structure of ZnO. A small change in crystallite size has been observed due to Dy doping in ZnO. AFM analysis ascertains the grain growth and smooth surface of the thin films. The Dy doped ZnO thin film exhibits a significant enhancement in UV region absorption as compared to the pure ZnO thin film, which suggests that Dy doped ZnO can be used as a UV detector. Under UV irradiation of wavelength 325 nm, the photocurrent value of Dy doped ZnO is 105.54 μA at 4.5 V, which is 31 times greater than that of the un-doped ZnO thin film (3.39 μA). The calculated value of responsivity is found to increase significantly due to the incorporation of Dy in the ZnO lattice. The observed higher value of photocurrent and responsivity could be attributed to the substitution of Dy in the ZnO lattice, which enhances the conductivity, electron mobility, and defects in ZnO and benefits the UV sensing property.

Structural, electrical, magnetic and thermal properties of Pr0.8-xDyxSr0.2MnO3 with (x = 0, 0.2 and 0.25)

In the present work we report structural, electrical, magnetic and thermo-power of Pr0.8-xDyxSr0.2MnO3 with (x = 0, 0.2 and 0.25) manganites. It is observed that Curie temperature TC decreases with Dy doping and also ZFC magnetization curves decrease more sharply with Dy from magnetization study. Though, Dy3+ ion has large magnetic moment μ = 10.65μB, because of its smaller ionic radius that of Pr3+ ion, changes in magnetic properties have observed. The zero field resistivity for pristine sample shows a small peak at around 157 K, near the metal-insulator transition temperature (TMI), which is also closer to the Curie temperature TC and a more pronounced peak at (Tf) around 95 K. All samples show the positive thermo-electric power throughout the temperature range.

Preparation, characterization and antibacterial property of rare earth (Dy and Ce) doping on ZrO2 nanoparticles prepared by co-precipitation method

Undoped and rare earth (Dysprosium and Cerium) doped ZrO2 nanoparticles (NPs) were synthesized by Co-precipitation Method (CPM). Urea has used as a precipitator and zirconyl nitrate, dysprosium (III) nitrate pentahydrate, cerium (III) nitrate hexahydrate as starting materials in a pre-heated furnace of around 600°C. The as-synthesized products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX) and Ultra-Violet (UVvis-DRS) analysis. XRD study revealed that the synthesized nanoparticles exhibited tetragonal (t- ZrO2) and monoclinic (m- ZrO2) phase of ZrO2 nanoparticles and also confirm the decrease in the crystallite size with Dy and Ce doping. It was observed that the shape of the nanoparticles is affected by the nature of dopant. EDX study confirmed the presence of Zr, Dy, Ce and O and appropriate increase in the Dy and Ce proportion in the final product. Diffuse reflectance results revealed that the addition of dopant significantly enhanced the optical bandgap value of 2.48, 2.51 and 2.62eV for undoped, Dy and Ce doped ZrO2 nanoparticles, due to basis of oxygen vacancies present within the samples. Furthermore, the undoped, Dy and Ce doped ZrO2 nanoparticles showed no toxicity and possessed a good antibacterial ability against both Bacillus Subtilis (B.subtilis) and Klebsiella Pneumoniae (K.pneumoniae) cell.

Study of the Structural and Optical Properties of Dy Doped CdS Thin Films Deposited by Close-spaced Vacuum SublimationCdSDy

Study of the Structural and Optical Properties of Dy Doped CdS Thin Films Deposited by Close-spaced Vacuum SublimationCdSDy

Study of some Luminescence Properties of Dy Doped CaSO4 Phosphor

Study of some Luminescence Properties of Dy Doped CaSO4 Phosphor

Achieving room temperature ferromagnetism in ZnO nanoparticles via Dy doping

The tunable room-temperature ferromagnetism (RTFM) of ZnO nanoparticles through Dy doping were fabricated through a simple co-precipitation method for spintronic device applications. The synthesized samples were analyzed by studying their structural, morphological, optical, chemical, and magnetic properties. X-ray diffraction, selected area electron diffraction, and X-ray photoelectron spectroscopy results display that the Dy3+ have successfully entered for a few of the Zn2+ as a substitute in the ZnO crystal lattice without altering their hexagonal structure. Morphology studies of the suspensions consist of monodisperse and slightly hexagonal shaped nanoparticles. The tunable optical band gap was observed in the ZnO samples via Dy doping, confirmed by diffuse reflectance spectroscopy studies. Declaration of RTFM of the ZnO:Dy has been established with the noticed hysteresis in M–H loops and these studies indicate that the saturation magnetization of the ZnO sample as a function of Dy content. Amalgamating with the above results, it is suggested that, the observed RTFM in the ZnO:Dy nanoparticles may be interpreted by the contribution of the magnetic moments from the unpaired 4f electrons of Dy3+ ions.