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"

Microscopic spin Hamiltonian for a dipolar-Heisenberg magnet LiGdF4 from EPR measurements

Low-temperature electron paramagnetic resonance measurements are performed on single crystals of LiY_{1-x}Gd_xF_4 with weak x=0.005 and moderate x=0.05 concentration of Gd ions. Modeling of the experimental spectra allows us to precisely determine microscopic parameters of the spin Hamiltonian of the parent LiGdF4 material, including the nearest-neighbor exchange constant. The obtained parameters are further tested by comparing a strongly anisotropic Curie-Weiss temperature obtained for LiGdF4 in our static magnetization measurements with theoretically computed values. We find a fine balance between principal magnetic interactions in LiGdF4, which results in a hidden magnetic frustration presumably leading to a delayed magnetic ordering and an enhanced magnetocaloric effect at low temperatures.Comment: 6 pages, 6 figure

Microwave-Assisted Hydrothermal Synthesis and Annealing of DyF 3

The series of DyF3 nanosized samples was synthesized by the colloidal chemistry method. The microwave-assisted hydrothermal treatment was used for the first time for the modification of DyF3 nanoparticles. Transmission electron microscopy images show that the DyF3 nanoparticles have average particle size of about 16–18 nm and the size distribution becomes narrower during the microwave irradiation. The X-ray diffraction analysis shows the narrowing of the diffraction peaks versus microwave treatment time. The experimental data demonstrates restructuring of the nanoparticles and their crystal structure becomes closer to the ideal DyF3 regular structure during the microwave irradiation of colloidal solution. The defect-annealing model of the microwave-assisted hydrothermal modification process is suggested

5d-4f luminescence of Ce3, Gd3 and Lu3 in LiCaAlF6

The emission and excitation spectra as well as decay kinetics of luminescence due to 5d4f transitions in Ce3, Gd3 and Lu3 ions doped into LiCaAlF6 crystals have been analyzed with high spectral and time resolution using synchrotron radiation for excitation. The rich fine structure originating from electronic origins of transitions and their phonon replica has been well resolved and identified. Experimental data are compared with the spectra simulated in the framework of the semiphenomenological models of the crystal field and the crystal lattice dynamics. © 2011 Elsevier B.V. All rights reserved

Vacuum-ultraviolet 5d-4f luminescence of Gd3+ and Lu3+ ions in fluoride matrices

The VUV 4 f n-1 5d-4 f n luminescence and luminescence excitation spectra of Gd3+ (n=7) in LiGdF4, GdF3, LiYF4: Gd3+, and YF3: Gd3+, and of Lu3+ (n=14) in LiLuF4, LuF3, and LiYF4: Lu3+ have been analyzed with high spectral resolution. In systems with intermediate electron-phonon coupling, zero-phonon lines, and phonon sidebands were observed. The excitation spectra of dilute systems exhibit rich fine structure originating from electronic origins of transitions and their phonon replica. Theoretical calculations explicitly taking into account a microscopic model of the crystal field and the crystal lattice vibrational spectra agree well with experimental data and are the basis for a safe analysis of the spectra. © 2007 The American Physical Society

EPR and optical spectroscopy of neodymium ions in KMgF3 and KZnF3 crystals

KMgF3 and KZnF3 crystals doped with Nd3+ ions were studied using EPR and optical spectroscopy methods. Several types of paramagnetic centers of Nd3+: KMgF3 - two of tetragonal and one of rhombic symmetry; KZnF3 - one of tetragonal and one of trigonal symmetry were found. Parameters of the corresponding spin Hamiltonians were determined. Using optical spectroscopy paramagnetic centers Nd2+ and Nd4+ in KMgF3 were found. © 1993 Springer

NMR, high frequency EPR and magnetization studies of YF 3:Tm 3+ and TmF 3

Magnetic properties of single crystal and powder samples of thulium fluoride, TmF 3 (orthorhombic Pnma space group), and single crystals of YF 3 doped with the Tm 3+ ions are studied by NMR, high-frequency EPR and dc-magnetometry. It is shown that TmF 3 is a Van Vleck paramagnet. Zero field splitting between two lowest ground state energy levels (ground 3H 6 multiplet) of Tm 3+ ion in TmF 3 crystal lattice is found to be ∼6.5 cm -1. The 19F nuclear spin-lattice relaxation in TmF 3 at liquid helium temperatures is driven by the fluctuating magnetic fields created by Tm 3+ ions occupying the lowest excited singlet

Теплопроводность монокристаллов твердых растворов на основе диоксида циркония, стабилизированных оксидами скандия, иттрия, гадолиния и иттербия

The phase composition and heat conductivity of (ZrO2)0.9(R2O3)0.1 solid solution single crystals have been studied, where R = (Gd, Yb, Sc, Y), (ZrO2)0.9(Sc2O3)0.09(Gd2O3)0.01 and (ZrO2)0.9(Sc2O3)0.09(Yb2O3)0.01. Single crystals have been grown by directional melt crystallization in a cold skull. The phase composition of the crystals has been studied using X-ray diffraction and Raman spectroscopy. The heat conductivity of the crystals has been studied using the absolute steady-state technique of longitudinal heat flow in the 50—300 K range. We show that at a total stabilizing oxide concentration of 10 mol.% the phase composition of the crystals depends on the ionic radius of the stabilizing cation. The (ZrO2)0.9(Sc2O3)0.1 crystals have the lowest heat conductivity in the 50—300 K range while the (ZrO2)0.9(Gd2O3)0.1 solid solutions have the lowest heat conductivity at 300 K.Analysis of the experimental data suggests that the heat conductivity of the crystals depends mainly on the phase composition and ionic radius of the stabilizing cation. Phonon scattering caused by the difference in the weight of the co-doping oxide cation has a smaller effect on the heat conductivity.В работе приведены результаты исследования фазового состава и теплопроводности кристаллов твердых растворов (ZrO2)0,9(R2O3)0,1 где R = (Gd, Yb, Sc, Y), (ZrO2)0,9(Sc2O3)0,09(Gd2O3)0,01 и (ZrO2)0,9(Sc2O3)0,09(Yb2O3)0,01. Кристаллы выращивали методом направленной кристаллизации расплава в холодном контейнере. Исследования фазового состава кристаллов проводили методом рентгеновской дифрактометрии и комбинационного рассеяния света. Теплопроводность кристаллов изучали абсолютным стационарным методом продольного теплового потока в интервале температур 50—300 К.Показано, что при суммарной концентрации стабилизирующих оксидов 10 % (мол.) фазовый состав кристаллов зависит от величины ионного радиуса стабилизирующего катиона. Минимальные значения теплопроводности в диапазоне температур 50—150 K имеют кристаллы (ZrO2)0,9(Sc2O3)0,1, а при температуре 300 К — твердые растворы (ZrO2)0,9(Gd2O3)0,1.Анализ полученных данных позволяет сделать вывод о том, что основное влияние на теплопроводность оказывает фазовый состав и величина ионного радиуса стабилизирующего катиона. При этом фононное рассеяние, связанное с различиями массы катионов солегирующего оксида, оказывает на теплопроводность меньшее значение

Electrophoretic studies on phosphatases from the pancreatic islets of obese-hyperglycaemic mice.

EPR spectra of isostructural LiYF4 and LiLuF4 crystals doped by Dy3+, Er3+, and Ho3+ ions are measured at 4.2 K in the frequency range 40-800 GHz. The effects caused by isotopic disorder in the lithium sublattice, the random crystal field, and the interaction between paramagnetic impurity ions are detected and studied. The results of the measurements are used to determine the spectral characteristics of the compounds and the crystal field parameters. It is demonstrated that the formation of the isotope structure of the EPR signal is dominated by local deformations of the crystal lattice induced by mass defects. © 2008 Pleiades Publishing, Ltd