Set Of Crystal Field Parameters Research Articles

Crystal field in praseodymium gallium garnet

To study the crystal field (CF) at praseodymium sites in praseodymium gallium garnet (PrGG) we investigated experimentally and theoretically its Raman scattering, magnetization, and far infrared magnetotransmission. The experimental data can be described by a set of CF parameters which are rather close to those available for analogous neodymium-doped rare earth gallium garnets.

Crystal-field effects and simulation of the energy level scheme of Nd3+ in magnesium borate MgNd(BO2)5

Based on the energy level scheme of Nd3+ derived from the absorption spectra for MgNd(BO2)5, S.G. P21/c, at temperatures of 300, 77 and 9 K, a phenomenological parametrization of the free-ion and crystal-field effects was carried out. A descending symmetry method, from C2v to C2 symmetries, was used in the simulation of the configuration, leading to low r.m.s. deviation values. The crystal-field parameter sets are consistent with that corresponding to the same Eu3+-doped borate matrix for each of these considered symmetries. Very good agreement of the observed crystal-field strength parameters is found when they are compared with the ab initio parameters calculated from crystal data for C1, the real point symmetry of Nd3+ in the matrix.

Spectroscopy and dynamics of 5f states of Es 3+ in LaF 3

Using time- and wavelength-resolved laser-induced fluorescence methods, the 5f state spectroscopy and photodynamics of 253Es 3+ in LaF 3 have been investigated. Based on an effective operator Hamiltonian model and approximating the metal ion site symmetry as C 2 v , a set of crystal field parameters has been obtained that fit the 56 assigned levels associated with the seven states of Es 3+ that were observed. The 5F 5 emitting state of Es 3+ exhibited a decay rate that approached the expected purely radiative decay of the state. This suggests that the shorter lifetime previously found for this state of Es 3+ in LaCl 3 arose from radiation damage induced by α decay of 253Es.

Electron paramagnetic resonance investigation of ions in single crystals

An X-band electron paramagnetic resonance study at 5 K of ions in single crystals is reported. The spectra have been attributed to a unique centre of located at the site. The spin-Hamiltonian parameters have been determined for the even isotopes of Dy, as well as for the isotopes and . Moreover, a detailed g-factor analysis has been carried out by obtaining the ground doublet wavefunction. To this purpose, we have employed an interpolated set of crystal-field parameters for which was estimated from the fitted sets of and in . It is found that the interpolated set yields a satisfactory approach to the experimental g-factor values, which makes it feasible to predict the energy-level scheme for the ground manifold of in this host.

Crystal-field splitting of energy levels of rare-earth ions Dy3+(4f9) and Yb3+(4f13) in M(II) sites in the fluorapatite crystal Sr5(PO4)3F

We have calculated a set of crystal-field parameters, Bnm, for Dy3+ through Yb3+ ions in M (II) sites in the crystal Sr5(PO4)3F (SFAP). The Bnm parameters were derived from lattice-sum calculations and from analyses of the optical spectra reported for Ho3+, Er3+, and Tm3+ individually doped into SFAP. These parameters were used to predict starting values, which were then semiempirically fitted for the crystal-field splitting of the multiplet manifolds of the sextet states of Dy3+(4f9), HJ6, and FJ6 and the doublet states of Yb3+(4f13) having manifolds F7/22 and F5/22. The results are compared with an analysis of the absorption and fluorescence spectra of Dy3+ and Yb3+ individually doped into SFAP. The rms deviation between 44 calculated and observed Stark levels of Dy3+ in Dy:SFAP is 10 cm−1. Without fitting of any parameters, the predicted crystal-field splitting of the Yb3+ multiplet manifolds is in reasonable agreement with the observed spectra for Yb:SFAP.

Crystal Structures and Electronic Absorption Spectra of Two Modifications of Cr(SeO2OH)(Se2O5)

Single crystals of two modifications (I and II) of Cr(SeO2OH)(Se2O5) have been synthesized under low-hydrothermal conditions. Their structures have been investigated using single-crystal X-ray diffraction data up to sinθ/λ=0.76 Å−1[I: monoclinic, space groupP21/n,a=7.517(2) Å,b=12.516(3) Å,c=7.381(2) Å,β=91.46(1)°,Z=4,R1=0.030 for 1562Fo>4σ(Fo) and 114 variables; II: orthorhombic, space groupPnma,a=8.782(2) Å,b=11.172(3) Å,c=7.545(2) Å,Z=4,R1=0.031 for 752Fo>4σ(Fo) and 65 variables]. In Cr(SeO2OH)(Se2O5)-I, sheets—built up from isolated CrO6octahedra and Se2O5groups—are linked via the SeO2OH groups and rather strong hydrogen bonds. This structure is isotypic with the corresponding compounds of Mn(III) and Fe(III). Cr(SeO2OH)(Se2O5)-II represents a new framework structure type, also composed of isolated CrO6octahedra and Se2O5and SeO2OH groups, but with very weak hydrogen bonds. The hydrogen-bonding schemes of both compounds were further investigated by FTIR microscope spectrometry in the range 7000–1000 cm−1, yielding a typical AB-band spectrum for phase I. Furthermore, polarized electronic absorption spectra were measured in the range 33,000–12,500 cm−1using UV–VIS microscope spectrometric techniques. According to the weak distortions of the CrO6octahedra in both compounds, the observed band splittings and polarization effects are rather weak. Hence, crystal field calculations were performed assumingOhsymmetry, resulting in the following crystal field parameter sets; I,Dq=1558,B35=653,B55=760,C=2920 cm−1; II,Dq=1641,B35=647,B55=730,C=2815 cm−1. TheseDqvalues are slightly below average compared to octahedral Cr(III) in other oxygen-based structures, a tendency that was already observed for other 3dtransition elements in crystal fields of selenite compounds. This might indicate a rather low position of the [SeO3]2−anion within the range of oxygen-based ligands in the spectrochemical series.

Spectroscopic properties of LiErF4

Polarized absorption and magnetic circular dichroism (MCD) spectra of an LiErF4 single crystal have been recorded at different temperatures between liquid-helium temperature and room temperature. Assignments are made assuming D2d symmetry for the coordination polyhedron around the trivalent erbium ion. The energy level scheme is parametrized in terms of 20 free-ion and 5 Bqk crystal-field parameters. The optimized set of crystal-field parameters is: B02 = 303.3 cm−1, B04 = −773.3 cm−1, B44 = −935.0 cm−1, B06 = −59.9 cm−1 and B46 = −665.9 cm−1. Intensities of transitions between crystal-field levels are parametrized by a set of Atpλ intensity parameters. The reliability of the parameter sets is tested by graphical simulation of the experimental MCD spectra.

Ho:Tm:YLF laser amplifiers

A series of models is developed that describes a Ho:Tm laser, and predictions from these models are compared with experimental measurements for a variety of Ho:Tm:YLF amplifiers. Modeling is complicated by the plethora of required parameters needed to describe the dynamics of the Ho:Tm laser system versus the paucity of measured parameters. To remedy this, calculations presented here begin with measured energy levels and a quantum-mechanical model to determine a set of crystal-field parameters that are then used to calculate the energy-transfer parameters. Energy-transfer parameters, which describe the dynamics of energy exchange in the Ho:Tm system, are subsequently used in a rate-equation model to describe the dynamics of the lowest four manifolds of both Ho and Tm. Next, predictions of the rate-equation model are used in an amplifier model, which, among other effects, includes the variation of the pump energy density with the position of the probe beam in the amplifier. Results of the amplifier model are then compared with small-signal gain measurements from a variety of Ho:Tm:YLF laser amplifiers. Finally, the models are used to investigate the ultimate performance of a Ho:Tm:YLF laser amplifier by varying the concentrations of Ho and Tm in addition to the length of the end-pumped device.

Magnetic susceptibilities and crystalline electric field effects in single crystals of NdBa 2Cu 3O 7−δ

We report the directional magnetic susceptibilities on single crystals of NdBa 2Cu 3O 7− δ . Crystal field (CF) analysis considering orthorhombic symmetry at the Nd 3+ site has been performed and a best set of CF parameters have been obtained. The energy levels obtained from the present fit are in good agremment with the inelastic neutron scattering spectra.

Spectroscopic data on 2‐μm laser systems

Some of our recent spectral and energy transfer results on Tm3+-based 2-?m solid state laser systems are presented. Based on experimental data, with an improved algorithm and parameterized crystal field calculations, complete energy level diagrams for Tm3+ in YAG and GGG are obtained. The sets of crystal field parameters could be used to estimate a series of important spectral data for laser emission. A discussion of the spectral characteristics and the nature of Tm3+ multisite structure is also presented. The static spectral modifications in Cr3+ codoped with Tm3+ YAG or GGG crystals, due to mutual crystal field perturbations of the two dopants, are connected with Cr3+-Tm3+ pairs. The high-resolution data offer direct evidence that the Cr31-Tm3+ energy transfer is governed for near neighbor Cr3+(a)-Tm3+(c) pairs by a shortrange, most probably superexchange, interaction. The contribution of multipolar interactions should be considered only for more distant pairs, while at large distances, dipole-dipole interaction is dominant. The data suggest that the sensitization with Cr3+ determines not only an efficient way of transfer of excitation from the pumping sources to active ions but could produce changes of the spectal and temporal behavior of the latter.

Raman study of crystal-field excitations in Nd1.85Ce0.15CuO4.

Eighteen Raman active crystal-field (CF) excitations were detected in ${\mathrm{Nd}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_{4}$. They correspond to transitions within the $^{4}$${\mathit{I}}_{9/2}$, $^{4}$${\mathit{I}}_{11/2}$, and $^{4}$${\mathit{I}}_{13/2}$ multiplets associated with the inequivalent sites of the ${\mathrm{Nd}}^{3+}$ ion. Three sets of CF parameters which describe the observed energy spectra were derived. One of the three ${\mathrm{Nd}}^{3+}$ sets describes levels which are very similar to those observed in ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4}$ while the two others correspond to sites affected by the cerium doping. Kramers doublet splitting is also present indicating that antiferromagnetism persists in the ${\mathrm{CuO}}_{2}$ planes even with 7.5% cerium doping. \textcopyright{} 1996 The American Physical Society.

Energy levels of Tm3+ in yttrium aluminium garnet

An improved energy level diagram for Tm3+(4f12) ions in dodecahedral (D2 symmetry) sites in Y3Al5O12 (YAG) has been obtained from experimental absorption and emission spectra. Interferences in line assignment from the spectra of minority perturbed Tm3+ centres or due to electron-phonon interaction are discussed. A parametrized Hamiltonian that includes one-electron crystal-field interactions for D2 symmetry has been used to fit the experimental data. The RMS deviation between 70 experimentally determined levels (from the total of 90) and calculated levels is 9 cm-1 and the individual misfit is no larger than 20 cm-1 The analysis is based not only on the experimentally located energy levels, but also on the information concerning the symmetry labels for Stark levels. The obtained set of crystal-field parameters seems more suitable than the previously reported description of Tm3+ crystal-field energy levels in YAG.

Magnetic susceptibility and specific heat of Pr2?xCexCuO4?y

We report here the measurements of magnetic susceptibility of Pr2−xCexCuO4−y (x=0, 0.05 and 0.15) from 2K to 300K and the specific heat of Pr1.85Ce0.15CuO4 between 6K and 60K. Fitting of the magnetic susceptibility data to a Curie-Weiss law gave effective magnetic moment (peff) values close to the free ion value of 3.58μB for Pr3+. peff was found to decrease with increase in cerium concentration. The site symmetry of Pr3+ in Pr2−xCexCuO4−y (PCCO) host is D4h and a crystal field (CF) Hamiltonian appropriate to tetragonal symmetry was used to analyze the magnetic susceptibility data. J-mixing of all the thirteen multiplets of Pr3+ and intermediate coupled wave functions have been included. A best set of CF parameters obtained not only explains the magnetic susceptibility but also the inelastic neutron scattering spectra (INS) reasonably well. The Schottky component together with Debye and Einstein contributions successfully accounts for the measured specific heat.

Spectra of tetravalent chromium in calcium fluorophosphate

The spectroscopic properties of Cr-doped Ca5(PO4)3F known as Cr:FAP were examined using several different chemical and physical means. Results from analytical titration measurements indicate that chromium is tetravalent in the samples investigated. Based on electron-spin resonance measurements at temperatures as low as 11 K, no trivalent chromium and only a trace of pentavalent chromium (0.5–10 ppm) was detected in the samples used for optical studies. We postulate that Cr4+ is stabilized in the crystal as a result of the small amount of Y2O3 that was added during the crystal growth process and that charge balance is achieved when Y3+ replaces Ca2+ and Cr4+ replaces P5+. Assuming tetravalent chromium, absorption, and emission spectra were interpreted by analyzing phonon sidebands and zero-phonon transitions observed at various temperatures. The observed crystal-field splitting is compared with calculated levels based on a Tanabe–Sugano diagram for quartet and doublet states of Cr4+(3d2) in tetrahedral symmetry. The parametrized Hamiltonian includes the free-ion parameters for Cr4+(3d2) and an initial set of crystal-field parameters obtained from a point-charge lattice-sum calculation where ionic distances were obtained from x-ray crystallographic data. The parametrized Hamiltonian with crystal-field terms in C4 symmetry, when diagonalized within the complete 3d2 configuration, yields calculated Stark levels in reasonable agreement with levels established from the experiment.

Crystal field excitations of NdFeO3

The complete crystalline electric field (CF) spectrum of Nd3+ (4I93) in NdFeO3 has been determined at T = 18 K by using inelastic neutron scattering. The four excited energy levels (doublets) are at 10.4, 22.7, 45.4 and 60.8 meV. A set of crystal field parameters was found that describes the CF peak positions and intensities very well.

Crystal-field effect in ErCu2

The crystal-field contribution to the specific heat of the ErCu2 compound has been calculated using two lowest-order crystal-field parameters derived by Hashimoto et al. and a set of crystal-field parameters determined by Gubbens et al. The calculated results are compared with the experimental ones.

Determination of the crystal-field parameters for CePtSn

We have determined a set of crystal-field parameters for CePtSn which accounts for the available susceptibility, high-field magnetization at 4.2 K and inelastic neutron-scattering data. The analysis of experimental data revealed that the single-ion approach is reliable mainly at high temperatures (T>or=TN, TK) or at high magnetic fields where the energy associated with the exchange and coherence effects is much lower.

The correlation between the optical absorption spectrum and paramagnetic properties of neodymium trifluoride

The 4f3 configuration of Nd3+ in NdF3 has been revisited. The real point symmetry of the crystalline matrix-C2-has been considered for the simulation, which means 15 crystal field parameters (CFPs). The simulation has been conducted by considering together the energy level scheme derived from the optical absorption spectra and the paramagnetic susceptibility and its variation with the temperature and the g values of the ground level. It is shown that only a single set of CFPs reproduces this information correctly, whereas various sets are found if only the energy level scheme is retained in the simulation process.

Luminescence spectra and crystal field analysis of LaOBr doped with Tm3+

Crystal-field parameters (Bk,m) were obtained for LaOBr doped with Tm3+ from the analysis of luminescence spectra. The crystal-field Hamiltonian HCEF= Sigma kmBkm+ Sigma i Ckm(ri) for the C4v symmetry comprises five non-zero Bk,m parameters. The results of model crystal-field calculations in C4v symmetry for Tm3+ in LaOBr are compared with experimental data, for the lowest ten (S, L)J states 4f12 configuration. The set of crystal-field parameters (CFPs) calculated on the basis set of 54 sublevels reproduced the experimental level scheme within an RMS deviation of 11 cm-1.

Spin reorientation in Tb/sub 1-x/Y/sub x/Fe/sub 11/Ti compounds

The Tb/sub 1-x/Y/sub x/Fe/sub 11/Ti (x=0, 0.2, 0.4, 0.6 and 0.8) compounds have been studied in magnetization and AC-susceptibility measurements as a function of temperature. The results show that the Tb/sub 1-x/Y/sub x/Fe/sub 11/Ti compounds with x=0, 0.2 and 0.4 undergo a spin reorientation of the axis-to-plane type (referred to decreasing temperature), while the samples with x=0.6 and 0.8 remain easy-axis compounds down to the lowest temperature measured (4.2 K). The spin-reorientation temperature, T/sub sr/, is found to decrease with increasing Y content. The observed temperature dependence of the magnetic structure of this series of compounds has been analyzed on the basis of a crystal-field model with the following set of crystal-field parameters: B/sub 2//sup 0/=0.45 K, B/sub 4//sup 0/=-1.8/spl times/10/sup -4/ K and B/sub 6//sup 0/=0 K.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>