High resolution infrared absorption spectra, crystal field, and relaxation processes in CsCdBr_3:Pr^3+

High resolution low-temperature absorption spectra of 0.2% Pr^3+ doped CsCdBr_3 were measured in the spectral region 2000--7000 cm-1. Positions and widths of the crystal field levels within the 3H5, 3H4, 3F2, and 3F3 multiplets of the Pr^3+ main center have been determined. Hyperfine structure of several spectral lines has been found. Crystal field calculations were carried out in the framework of the semiphenomenological exchange charge model (ECM). Parameters of the ECM were determined by fitting to the measured total splittings of the 3H4 and 3H6 multiplets and to the observed in this work hyperfine splittings of the crystal field levels. One- and two-phonon relaxation rates were calculated using the phonon Green's functions of the perfect (CsCdBr_3) and locally perturbed (impurity dimer centers in CsCdBr_3:Pr^3+) crystal lattice. Comparison with the measured linewidths confirmed an essential redistribution of the phonon density of states in CsCdBr_3 crystals doped with rare-earth ions.Comment: 16 pages, 5 tables, 3 figure

Fine structure of spectral lines in LiYF4:Er3+ due to isotopic disorder in the lattice

We report the first observation of the resolved structure in the 4I(15/2) → 4I(13/2) infrared transition of LiYF4:Er caused by lithium isotopes of the lattice. Isotope shifts Of 0.019 and 0.016 cm-1 and inhomogeneous linewidths of 0.010 and 0.007 cm-1 were measured for the lines 6534.3 and 6538.3 cm-1, respectively. Unresolved structure due to different erbium isotopes totals ~ 0.010 cm-1. (C) 2000 Elsevier Science B.V

Optical spectra, crystal-field parameters, and magnetic susceptibility of the new multiferroic NdFe3(BO3)4

We report high-resolution optical absorption spectra for NdFe3(BO3)4 trigonal single crystal which is known to exhibit a giant magnetoelectric effect below the temperature of magnetic ordering TN = 33 K. The analysis of the temperature-dependent polarized spectra reveals the energies and, in some cases, symmetries and exchange splittings of Nd3+ 84 Kramers doublets. We perform crystal-field calculations starting from the exchange-charge model, obtain a set of six real crystal-field parameters, and calculate wave functions and magnetic g-factors. In particular, the values g(perpendicular) = 2.385, g(parallel) = 1.376 were found for the Nd3+ ground-state doublet. We obtain Bloc=7.88 T and |JFN|= 0.48 K for the values of the local effective magnetic field at liquid helium temperatures at the Nd3+ site and the Nd - Fe exchange integral, respectively, using the experimentally measured Nd3+ ground-state splitting of 8.8 cm-1. To check reliability of our set of crystal field parameters we model the magnetic susceptibility data from literature. A dimer containing two nearest-neighbor iron ions in the spiral chain is considered to partly account for quasi-one-dimensional properties of iron borates, and then the mean-field approximation is used. The results of calculations with the exchange parameters for Fe3+ ions Jnn = -6.25 K (intra-chain interactions) and Jnnn = -1.92 K (inter-chain interactions) obtained from fitting agree well with the experimental data.Comment: 13 pages, 8 figures, 2 table

Experimental and theoretical study of the crystal-field levels and hyperfine and electron-phonon interactions in LiYF4:Er3+

We have measured high resolution absorption spectra for the 4I15/2→4I13/2, 4I11/2 infrared transitions of Er3+ ions in LiYF4. Positions of crystal-field levels and their widths were precisely determined and analyzed. Hyperfine structure of 167Er totaling ∼0.2 cm-1 was observed. Experimental data are described by a theory that operates with a realistic model of the lattice dynamics and with the crystal-field parameters and electron-phonon coupling constants calculated in the framework of the exchange charge model. The hyperfine splittings of the odd mass number isotope 167Er are calculated taking into account both magnetic dipole and electric quadrupole hyperfine interactions. The simulated hyperfine structure is in good agreement with the experimentally observed one. The one-phonon relaxation rates within the 4I11/2 and 4I13/2 crystal-field manifolds are calculated using the correlation functions of the Er3+ ion and ligand displacements. The results of these calculations agree within an order of magnitude with the measured homogeneous linewidths of the corresponding zero-phonon transitions from the ground state at low temperatures. ©2000 The American Physical Society

High-resolution spectroscopy, crystal-field calculations, and quadrupole helix chirality of DyFe<inf>3</inf>(BO<inf>3</inf>)<inf>4</inf>

© The Authors, published by EDP Sciences. High-resolution polarized transmission spectra of Dy Fe 3 (BO 3 ) 4 single crystals were investigated in broad spectral (10-23000 cm -1 ) and temperature (3.5-300 K) ranges. Energies of the dysprosium levels in the paramagnetic and antiferromagnetic phases were determined. On the basis of these data and preliminary calculations in the frameworks of the exchange-charge model, we determined the crystal-field and Dy-Fe exchange interaction parameters of the Dy 3+ ions at sites with the point C2 symmetry corresponding to the enantiomorphic P3121 and P3221 space groups. The values of electronic quadrupole moments of the Dy 3+ ions were calculated, which enabled us to interpret results of the work [Usui et al., Nature Mater. 13, 611 (2014)] on the observation of domains of different quadrupole chirality in DyFe3(BO3)4

Spectroscopy of f-f transitions, crystal-field calculations, and magnetic and quadrupole helix chirality in DyF e3(B O3)4

© 2017 American Physical Society.We present the results of temperature- and polarization-dependent high-resolution optical spectroscopy studies of DyFe3(BO3)4 performed in spectral ranges 40-300cm-1 and 3000-23000cm-1. The crystal-field (CF) parameters for the Dy3+ ions in the P3121 (P3221) phase of DyFe3(BO3)4 are obtained from calculations based on the analysis of the measured f-f transitions. Recently, quadrupole helix chirality and its domain structure was observed in resonant x-ray diffraction experiments on DyFe3(BO3)4 using circularly polarized x rays [T. Usui, Y. Tanaka, H. Nakajima, M. Taguchi, A. Chainani, M. Oura, S. Shin, N. Katayama, H. Sawa, Y. Wakabayashi, and T. Kimura, Nat. Mater. 13, 611 (2014)10.1038/nmat3942]. Using the obtained set of the CF parameters, we calculate temperature dependencies of the electronic quadrupole moments of the Dy3+ ions induced by the low-symmetry (C2) CF component and show that the quadrupole helix chirality can be explained quantitatively. We also consider the temperature dependencies of the bulk magnetic dc-susceptibility and the helix chirality of the single-site magnetic susceptibility tensors of the Dy3+ ions in the paramagnetic P3121 (P3221) phase and suggest the neutron and resonant x-ray diffraction experiments in a magnetic field to reveal the helix chirality of field-induced magnetic moments

Isotope shifts in the spectra of LiLuF4:Ho3+ crystals due to the isotopic disorder in the lithium sublattice

The isotope shifts of lines in the spectra of the LiLuF4:Ho 3+ crystal in the range of the transitions 5I8 → 5I7, 5I6, and 5I5 caused by the isotopic disorder with respect to lithium are measured. The shifts of different lines amount to 0.01-0.036 cm -1. A comparison with the previously measured isotope shifts in the spectra of the LiYF4:Ho3+ crystal is made. © 2004 MAIK "Nauka/Interperiodica"

Crystal field and magnetic ordering in the Haldane-chain compound Er 2BaNiO5 as studied by optical spectroscopy

High-resolution absorption spectra of the chain compound Er 2BaNiO5 were measured in a wide range of frequencies (6000-20,000 cm-1) and temperatures (2.5-300 K). Energies of 38 crystal-field levels of Er3+ in a paramagnetic Er 2BaNiO5 were determined. Exchange splittings of crystal-field levels in the antiferromagnetically ordered state (TN = 34 K) were measured. Crystal-field calculations were performed and the obtained wave functions were used to calculate the temperature dependence of the magnetic susceptibility to be compared with the detailed experimental dependence measured in this work. © 2004 Elsevier B.V. All rights reserved