Transitions Of Nd3 Research Articles

Use of electromagnetically induced transparency for measurement of superhyperfine splitting of the levels of rare-earth metals doped in optical crystals

The results of experimental and theoretical investigations of the electromagnetically induced transparency regime on the 4 I 9/2-4 G 5/2 transition in Nd3+ ions doped in LaF3 are presented. The superhyperfine splitting of the upper and lower working levels has been determined on the basis of the results obtained. A theoretical model adequately describing the parameters of the resonances of electromagnetically induced transparency has been developed by analyzing the experimental data.

High Power Continuous-Wave and Acousto-Optic Q-Switched Nd:GdVO4 Laser Operated at 912 nm

We present a high power and efficient operation of the 4F3/2 → 4I9/2 transition in Nd:GdVO4 at 912nm. In the cw mode, the maximum output power of 8.6 W is achieved when the incident pump power is 40.3 W, leading to a slope efficiency of 33.3% and an optical-optical efficiency of 21.3%. To the best of our knowledge, this is the highest cw laser power at 912 nm obtained with the conventional Nd:GdVO4 crystal. Pulsed operation of 912 nm laser has also been realized by inserting a small acousto-optic (A-O) Q-Switch inside the resonator. As a result, the minimal pulse width of 20 ns and the average laser power 1.43 W at the repetition rate of 10 kHz are obtained, corresponding to 7.1 kW peak power. We believe that this is the highest laser peak power at 912nm. Furthermore, duration of 65ns has also been acquired when the repetition rate is 100kHz.

Order–disorder transition in Nd 2−yGd yZr 2O 7 pyrochlore solid solution: An X-ray diffraction and Raman spectroscopic study

Powder X-ray diffraction (XRD) and Raman spectroscopic study of order–disorder-phase transition with increase in the content of Gd in Nd 2− y Gd y Zr 2O 7 solid solution is being reported. It has been observed from Rietveld analysis that with increase in concentration of Gd in Nd 2− y Gd y Zr 2O 7, the value of the x parameter of the 48 f oxygen changes from 0.332(1) to 0.343(1) with a sudden change in the slope for y=1.8, which indicates that the structure is transforming from ordered pyrochlore to disordered pyrochlore. In addition to that a sudden and drastic change in the Raman spectra including changes in the position and width of several Raman modes beyond y⩾1.8 has also been observed which has been correlated with increasing disorder. Based on these studies, it is suggested that there is a discontinuous order–disorder transition from ‘perfect pyrochlore’ to ‘defect pyrochlore’ phase in Nd 2− y Gd y Zr 2O 7 solid solution.

Electromagnetically induced transparency on Zeeman sublevels in Nd3+:LaF3 crystals

The results of experimental observation of the electromagnetically induced transparency regime on the 4I9/2-4G5/2 transition in Nd3+ ions doping in LaF3 are presented. The depth and width of the transparency are analyzed as functions of the control field intensity.

Thickness Induced Superconducting Insulating Transition in ${\rm Nd}_{1.2}{\rm Ba}_{1.8}{\rm Cu}_{3}{\rm O}_{\rm z}$ Ultra-Thin Films

A study of the thickness induced superconducting to insulator transition in Nd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.2</sub> Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sub> (NdBCO) epitaxial films is presented. The samples have been deposited by high oxygen pressure diode sputtering on SrTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (100) substrates. Accurate structural characterizations have been carried out in function of the film thickness by X-ray diffraction using conventional and synchrotron radiation sources. The superconductor to insulator transition is correlated to a structural transformation from a pseudotetragonal phase, characterized by the presence of short Cu(1)O chains in both a and b directions, to a tetragonal structure where Cu(1)O chains are completely destroyed. We demonstrate that the ordering of oxygen ions is essential for the appearance of the superconductivity, while oxygen disorder in the Cu(1)O planes, leads to a two-dimensional MOTT insulating behavior of the resistivity associated to a localization of the carriers within lengths lower than 3 nm.

Effect of pressure on the luminescence properties of Nd3+ doped SrWO4 laser crystal

Abstract The luminescence spectra of the 4 F 3/2 → 4 I 9/2 transition of Nd 3+ ions in a SrWO 4 crystal have been analyzed as a function of pressure at room temperature. Experiments have been performed in a diamond-anvil cell up to 13 GPa. At around 10 GPa some changes in the emission spectra have been observed which are attributed to a structural phase transition of the SrWO 4 matrix. These results are in good agreement with a previous paper, in which in a pure SrWO 4 matrix a scheelite to fergusonite phase transition is found around 10.5 GPa. Moreover, with increasing pressure, the decay curves from the 4 F 3/2 are nonexponential and faster indicating that the energy transfer processes between Nd 3+ ions are important.

Crystal structure of Ln1/3NbO 3 ( Ln=Nd, Pr) and phase transition in Nd 1/3NbO 3

The crystal structure of the A-site deficient perovskite Ln 1/3NbO 3 ( Ln=Nd, Pr) at room temperature has been determined, for the first time, as orthorhombic in space group Cmmm using high-resolution neutron powder diffraction. Pertinent features are the alternation of unoccupied layers of A-sites and layers partly occupied by Ln cations, as well as out-of-phase tilting of the NbO 6 octahedra around an axis perpendicular to the direction of the cation/vacancy ordering. The phase transition behaviour of Nd 1/3NbO 3 has also been studied in situ. This compound undergoes a continuous phase transition at around 650 °C to a tetragonal structure in space group P4/ mmm due to the disappearance of the octahedral tilting. The analysis of spontaneous strains shows that this phase transition is tricritical in nature.

Superconducting to insulating transition in Nd 1.2Ba 1.8Cu 3O 7+ x thin films studied by polarized X-ray absorption spectroscopy

We report a study of the superconducting-insulator (S-I) transition in epitaxial untwinned Nd 1.2Ba 1.8Cu 3O 7+ x films using Cu–L and O–K edge polarized X-ray absorption spectroscopy (XAS). The S-I transition in realized by reducing the films thickness from 9 to 6 u.c. Due to strain, thin NdBCO films are characterized by structurally identical CuO 2 planes. The major differences in the XAS spectra are not associated to states within the CuO 2 units in the ab-plane, but to the unoccupied 3d(3 z 2– r 2) states of copper at the Cu(1) and Cu(2) sites hybridized with the apical 2p( z) O(4) state, and to the unoccupied 2p( z) O(4) states themselves. The experimental results show that the S-I transition induced by change of thickness in Nd 1.2Ba 1.8Cu 3O 7+ x films is correlated to holes localization at the copper sites of the Cu(1)O charge reservoir layer. The results open new perspectives for the interpretation of the superconducting to insulating transition in the HTS compounds.

Asymmetrical phase separation in Nd 0.25La 0.25Ca 0.5MnO 3

The highly metastable region across the metal–insulator transition in Nd 0.25La 0.25Ca 0.5MnO 3 is probed by transport and magnetic measurements. The metal–insulator transition observed around 130 K is associated with large thermal hysteresis between temperatures 50–150 K. Observation of minor hysteresis loops across the region indicates coexistence of both metallic and insulating phases. The field-cooled heating and the zero-field-cooled heating susceptibilities deviate from each other from 205 K, signifying thermo-magnetic irreversibility arising from magnetic pinning and/or glassy magnetic behaviour. The magnetoresistance measured on the heating and cooling loops are found to be different in magnitude and nature. The cooling-cycle magnetoresistance was found to be highly irreversible with an open-ended hysteresis loop. We also observe change in the nature of the magnetic relaxation data on the heating and cooling protocols. This indicate strong thermal history dependence of magneto-transport behaviour in the present compound.

Synthesis and photoluminescent properties of neodymium-ion doped perovskite oxides

The visible transitions of Nd 3+ ions were found in the Nd x (Ca 1− x− y− z ,Ba y ,Sr z) TiO 3 system. All the compositions exhibit a pseudo-cubic structure. Based on the diffused reflectance spectra, the valence-to-conduction band edge for this system appears at 335 nm. A bright red luminescence at 613 nm is formed under excitation at 335 nm for all the compositions with x = 0.002 – 0.005 . With an increase in the dopant concentration of neodymium ions, the excitation and emission intensities both increase up to x = 0.005 of neodymium substitution. There is no shift in the excitation and emission spectra of the samples. This report is believed to be the first one in the literature to demonstrate strong visible emission from neodymium-doped oxide systems.

Interaction between amorphous silicon nanoclusters and neodymium ions

The luminescent infrared transitions in Nd3+ can be activated via a transfer mechanism from amorphous silicon nanoclusters. The Nd photoluminescence (PL) has some unusual characteristics, including a weak temperature dependence of the PL intensity. The data are explained using a simple rate equation model which enables an effective nanocluster-to-neodymium transfer time of ∼0.15μs to be extracted. This is short enough to dominate the intrinsic nanocluster decay rates at low temperatures but long enough to imply that the coupling between the nanoclusters and the Nd ions is, in fact, weaker than for Nd-doped bulk silicon or other semiconductors.

Fine structure of the field-induced magnetic transition in Nd 0.1La 0.9Fe 11.5Al 1.5

For the Nd 0.1La 0.9Fe 11.5Al 1.5 compound, the fine structure of the magnetic transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) states has been studied carefully by means of magnetization ( M ) and heat capacity ( C p ) measurements. Although a single phase with the cubic NaZn 13-type structure (Fm3c) has been proved by the room temperature X-ray diffraction pattern, the phase transition has been clearly found to be a stepwise process in M ( T ) and C p ( T ) curves under proper fields. Due to the strong competition between the FM order and AFM order, the characteristic is especially evident under low fields, weakens gradually with the increasing applied field and finally vanishes when the field is higher than 2 T. This multi-step magnetic transition results from the inhomogeneity of the sample, probably due to the inhomogeneous distribution of Nd atoms.

Mid-IR transitions of trivalent neodymium in low phonon laser crystals

Mid-IR Nd 3+ transitions perspective for laser oscillation were analyzed in the CaGa 2S 4, PbGa 2S 4, and PbCl 2 crystals and compared with low phonon fluoride crystals. Fluorescence kinetics decay of the high-lying 4G 7/2 and 4G 5/2; 2G 7/2 and low-lying 4I J levels and its temperature dependence in the range of 13–295 K were measured. For 5 μm mid-IR transitions of Nd 3+ the radiative relaxation rates are found to be several times higher and multiphonon relaxation (MR) rates are several times lower in lead and calcium thiogallate crystals compared to low phonon fluoride crystals. MR rate dependence on the Nd 3+ to the nearest ligand distance R 0 is established experimentally and analyzed in the frame of point-charge model of nonlinear theory of multiphonon relaxation. Mid-IR Nd 3+ 4–5.5 μm fluorescence spectra of 4I i – 4I j transitions perspective for laser oscillation were measured for the first time in the studied crystals.

Inter- and Intraconfigurational Transitions of Nd3+ in Hexafluoroelpasolite Lattices

Excitation of the 4f3 ion Nd3+ in hexafluoroelpasolite lattices by synchrotron radiation of wavelength approximately 185 nm leads to fast 4f(2)5d --> 4f3 emission below 52,630 cm(-1) and slower 4f3 --> 4f3 emission from the luminescent states (4)F(3/2) gamma8u (11 524 cm(-1)) and 2G2(9/2) gamma8u (approximately 47,500 cm(-1)). The near-infrared emission is well-resolved, and a clear interpretation of the 4I(9/2) crystal field levels and of the one-phonon vibronic sideband is given. The excitation spectrum of the 2G2(9/2) emission enables clarification of the structure of the 4f(2)5d configuration (which extends from approximately 52,000 to 128,000 cm(-1)). Detailed energy level and intensity calculations have been performed, which provide simulations of the d-f emission and the f-d excitation spectra in good agreement with experiment. It is interesting that although the 4f3 2G2(9/2) gamma8u --> 4f3 4I(J) transitions are very weak in intensity compared with transitions terminating upon higher multiplet terms, most of the 4f(2)5d (3H) 4I(9/2) gamma8g --> 4f3 emission intensity resides in the transitions to 4I(J).

Spectroscopic investigations of Nd 3+ ions in B 2O 3–PbO–Al 2O 3–WO 3 glasses

Spectroscopic properties of Nd 3+ ions in B 2O 3–PbO–Al 2O 3–WO 3 glasses have been reported. The spectroscopic parameters have been determined from absorption and emission measurements together with Judd–Ofelt analysis. Addition of lead oxide to the borate matrix significantly increases radiative parameters like radiative transition rate, measured lifetime, quantum efficiency and peak stimulated emission cross-sections. Three emission lines at 904, 1061 and 1335 nm have been registered in lead borate-based glass, which correspond to the transitions originating from the 4F 3/2 level to the 4I 9/2, 4I 11/2 and 4I 13/2 levels of Nd 3+ ions, respectively. Quite large room temperature peak stimulated emission cross-section has been obtained for 4F 3/2– 4I 11/2 transition of Nd 3+ ions in lead borate based glass, which is promising for NIR laser application at 1061 nm.

Synthesis and Photophysical Properties of Luminescent Lanthanide Complexes Based on Dansyl-N-Methyl-Aminobenzoic Acid for Advanced Photonics Applications

ABSTRACT Novel luminescent Ln(III)-chelated complexes based on dansyl-N-methyl-aminobenzoic acid exhibited the strong near IR emission bands of the characteristic 4I13/2 → 4I15/2 transition of Er(III) ion around 1530 nm and the characteristic 4F3/2 → 4F9/2, 4F3/2 → 4F11/2 and 4F3/2 → 4F13/2 transitions of Nd(III) ion around 880, 1060 and 1330 nm. Their photoluminescence intensity depends on the degree of the spectral overlap between the emission band of the ligand and the absorption band of lanthanide(III) ion. The radiative life times of Er(III) and Nd(III) ions in the lanthanide(III) complex films were estimated to be 1.6 and 1.2 μs, respectively.

Charge order melting and magnetic transition in Nd 0.5(1+ x) Ca 0.5(1− x) Mn (1− x) Cr xO 3 system

The magnetic property of double doped manganite Nd 0.5(1+ x) Ca 0.5(1− x) Mn (1− x) Cr x O 3 with a fixed ratio of Mn 3+:Mn 4+=1:1 has been investigated. For the undoped sample, it undergoes one transition from charge disordering to charge ordering (CO) associated with paramagnetic (PM)-antiferromagnetic (AFM) phase transition at T<250 K. The long range AFM ordering seems to form at 35 K, rather than previously reported 150 K. At low temperature, an asymmetrical M– H hysteresis loop occurs due to weak AFM coupling. For the doped samples, the substitution of Cr 3+ for Mn 3+ ions causes the increase of magnetization and the rise of T c. As the Cr 3+ concentration increases, the CO domain gradually becomes smaller and the CO melting process emerges. At low temperature, the FM superexchange interaction between Mn 3+ and Cr 3+ ions causes a magnetic upturn, namely, the second FM phase transition.

Thermal diffusivity and critical behavior of Nd 1−xSr xMnO 3

Thermal diffusivity measurements on Nd 1− x Sr x MnO 3 (0⩽ x<0.5) single crystals have been performed by means of a photopyroelectric technique in the temperature range 78–320 K. The critical exponents of the antiferromagnetic–paramagnetic transition in the undoped sample, as well as those of the ferromagnetic–paramagnetic transition in Nd 0.6Sr 0.4MnO 3, have been obtained through the analysis of the inverse of the thermal diffusivity. For x = 0 , the results agree with the Heisenberg model ( α Heisenberg = - 0.115 ), while for x = 0.4 , they point to the Ising model ( α Ising = + 0.110 ).

Quantum cutting in Gd xY 1−xLiF 4: Nd—dynamics and mechanisms

Nd 3+-sensitized quantum splitting for the Gd 3+–Nd 3+ couple is studied in mixed Gd x Y 1− x LiF 4: Nd phosphors as a function of the Gd 3+ concentration. Quantum splitting is observed for all samples studied which include the concentration range 0.1 < x < 1 . After excitation of the 4f 25d state of Nd 3+, rapid energy transfer occurs to Gd 3+ as evidenced by the decrease of 4f 25d emission with increasing x. The quantum splitting involves a cross relaxation in which the 6G state of Gd 3+ undergoes a downward transition to its lower lying 4f 7 levels with the simultaneous transition of Nd 3+ from its ground state to an excited state in the 4f 3 configuration that is resonant with the Gd 3+ downward transition. The dynamics are strongly affected by x. For x < 0.2 5 , the buildup of the 6P emission of Gd 3+ has two distinct components with very different time scales, microseconds and milliseconds. The rate of the fast component increases with a reduction in x. This points to the role of energy migration among Gd 3+. The slower time scale is similar to that of isolated Gd 3+ ions. The existence of these two very distinct temporal regimes points to the importance of exchange, which is a very short range interaction, in the quantum cutting process.

Optical and luminescence properties ofNd3+ ions in K–Ba–Al-phosphate and fluorophosphate glasses

Phosphate (PKBAN: P2O5+K2O +BaO +Al2O3+Nd2O3) andfluorophosphate (PKBFAN: P2O5+K2O +BaO +BaF2+Al2O3+Nd2O3 and PKBAFN: P2O5+K2O +BaO +Al2O3+AlF3+Nd2O3) glasses were prepared with three concentrations (0.1, 1.0 and 2.0 mol%) ofNd3+ ionsand their detailed luminescence properties have been investigated. Absorption spectra for 1.0 mol%of Nd3+-doped glasses have been analysed using Judd–Ofelt (JO) theory. The observed bands inabsorption spectra from ground to excited states are assigned and analysed with theparameterized free-ion Hamiltonian model. The JO parameters have been used topredict radiative properties for (J = 15/2, 13/2,11/2 and9/2) transitionsof Nd3+ ions in these glasses. The Inokuti–Hirayama model has been applied to the non-exponentialbehaviour of the decay profiles to investigate the mechanism involved in the energy transferbetween the donors and acceptors.