On the hyperfine interaction in rare-earth Van Vleck paramagnets at high magnetic fields

An influence of high magnetic fields on hyperfine interaction in the rare-earth ions with non-magnetic ground state (Van Vleck ions) is theoretically investigated for the case of $Tm^{3+}$ ion in axial symmetrical crystal electric field (ethylsulphate crystal). It is shown that magnetic-field induced distortions of $4f$-electron shell lead to essential changes in hyperfine magnetic field at the nucleus. The proposed theoretical model is in agreement with recent experimental data.Comment: 4 pages, no figures, submitted to J. Phys. : Cond. Mat

Electron Spin-Lattice Relaxation of Er3+ ions in Er0.01Y0.99Ba2Cu3Ox

The temperature dependence of the electron spin-lattice relaxation SLR was studied in Er0.01Y0.99Ba2Cu3Ox compounds. The data derived from the electron spin resonance ESR and SLR measurements were compared to those from inelastic neutron scattering studies. SLR of Er3+ ions in the temperature range from 20 K to 65 K can be explained by the resonant phonon relaxation process with the involvement of the lowest excited crystalline-electric-field electronic states of Er3+. These results are consistent with a local phase separation effects. Possible mechanisms of the ESR line broadening at lower temperatures are discussed. Keywords: YBCO; EPR; ESR; Electron spin-lattice relaxation time, T ; Crystalline-electric-fieldComment: 6 pages, 4 figure

Polishing surface layer of LiYF4 single crystal

By using methods of optical microscopy, microhardness and fast electrons diffraction in reflection mode it was determined that after mechanical polishing the depth of distorting layer is about 30 μm. Optimal results for layer etching were obtained by using KOH at 60°. The distortionless surface at LiYF4 single crystal was produced by mechanical polishing with chemical and ion-beam etching

Investigation of surface layer of polished LiYF4 single crystal

Optical microscopy, measurements of microhardness, and electron backscattering have been used to investigate the surface of an LiYF4 single crystal. The depth of the deformed layer after mechanical polishing was found to be 30 μm. In layer-by-layer etching of the crystal, the best results were obtained using KOH at 60°. A surface with a structure close to that of the matrix was obtained by mechanical polishing combined with chemical and ion-beam etching

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

EPR and spin-lattice relaxation of rare-earth ions in LiLuF4 monocrystals

The EPR and spin-lattice relaxation are studied of impurity rare-earth ions in LiLuF4 crystals at liquid-helium temperatures. It is detected that paramagnetic relaxation of Er3+ ions is retarded by the effect of the phonon throat. The effect of resonance attenuation of the phonon throat is clarified in two-phonon resonance relaxation processes of Er3+ ions. The Debye temperature of the crystal is determined from an analysis of experimental results. © 1988 Plenum Publishing Corporation

Induced quadrupole effects near a crossover in a tetragonal TbLiF 4 sheelite in a strong magnetic field up to 50 T

The anomalies of magnetic properties of TbLiF4 caused by the interaction of the energy levels of a rare-earth ion in a strong magnetic field up to 50 T directed along the [100] and [110] axes are studied experimentally and theoretically. The jumps in magnetization M(H) and the maxima of the differential magnetic susceptibility dM(H)/dH are found in critical fields H c = 28 and 31 T, where the lower component of the excited doublet approaches the ground-state singlet of a Tb3+ ion. Based on the crystal-field model with known interaction parameters, we calculated the Zeeman effect and the magnetization and magnetic susceptibility curves for the TbLiF4 crystal, which adequately describe magnetic anomalies and critical parameters of a crossover. It is shown that the jumpwise change in the α- and γ-symmetry quadrupole interactions in TbLiF4 caused by changes in the corresponding quadrupole moments during the crossing of energy levels leads, in accordance with experiments, to a decrease in the critical field H c by approximately 4 T and an increase in the maximum of the differential susceptibility dM(H)/dH near the crossover more than twofold. This behavior can be considered as an analog of the induced quadrupole transition caused by a change of the ground state of the rare-earth ion during crossover. © 2012 Pleiades Publishing, Ltd

The nonlinear Zeeman and parastriction effects in luminescence spectra of LiY1-xTmxF4 (0.02 ≤ x ≤), crystals

Splitting of the first excited Γ341(H63) doublet state of Tm3+ ions in the LiY1-xTmxF4 crystals in external magnetic fields up to 5.5 T has been studied using measurements of luminescence spectra at low temperatures. In the magnetic field perpendicular to the S4-symmetry axis of the crystal lattice, the splitting of the non-Kramers doublet is caused by the joint action of the nonlinear Zeeman effect and the piezospectroscopic effect related to parastriction. Experimental dependences of the doublet splitting on the magnetic field strength and direction are in good correspondence with the theoretical estimations obtained in the framework of the semiphenomenological crystal field model. It is shown that spectroscopic data present direct information on the forced magnetostriction in the basal plane of uniaxial Van Vleck paramagnets that contain non-Kramers rare earth ions. The measured concentration dependence of the doublet splitting can be explained by taking into account variations of the elastic constants with the concentration of Tm3+ ions. © 2005 Elsevier B.V. All rights reserved

All-solid-state subnanosecond tunable ultraviolet laser sources based on Ce3+-activated fluoride crystals

Several practical all-solid-state tunable ultraviolet subnanosecond laser sources have been developed based on Ce3+:LiLuF4 (Ce:LLF) and Ce3+:LiCaAlF6 (Ce:LiCAF) active media pumped by the fifth and fourth harmonics of a regular Q-switched 10-ns Nd:YAG laser, respectively. The demonstrated tuning range of the Ce:LiCAF oscillator providing reproducibly-single-pulse output was 282 nm to 314 nm with the maximum output energy of 1 mJ. Tunable laser output from 223 nm to 232 nm was obtained by sum-frequency-mixing Ce:LiCAF laser output with fundamental output of a Q-sw Nd:YAG laser. The maximum subnanosecond Ce:LiCAF single-pulse output of 14 mJ was obtained in a "master oscillator-power amplifier" (MOPA) configuration