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Title: Electric-field-gradient tensor and boron site-resolved {sup 11}B NMR in single-crystalline YB{sub 12}

Abstract

{sup 11}B NMR measurements on a single crystal of YB{sub 12} have been performed at room temperature at a frequency of 128.4 MHz. The electric-field-gradient (EFG) tensor components and the principal axes calculated previously by first-principles methods have been verified experimentally. Three magnetically different boron-atom groups in the B{sub 12} cluster were clearly observed for the crystal orientation used in this work. This distinction results from different EFG-tensor orientations with respect to magnetic field and not from different quadrupolar splittings ({nu}{sub Q}) or asymmetry-parameter values ({eta}). The magnetically different boron atoms have been identified through the calculated angle dependence of the satellite transitions (0 deg. -360 deg.). Very satisfactory agreement between the calculated and experimental angular dependencies of the EFG tensor has been obtained. Similarly, the quadrupolar splittings and asymmetry parameters agree very well with those previously determined from NMR measurements on a powder sample of YB{sub 12}.

Authors:
;  [1];  [2]; ;  [3]; ;  [4]
  1. Institute of Physics, A. Mickiewicz University, Umultowska Street 65, 61-614 Poznan (Poland)
  2. Institut fuer Physikalische Chemie, Universitaet Wien, Waehringer Strasse 42, 1090 Vienna (Austria)
  3. Institute for Low Temperature and Structure Research, Polish Academy of Sciences, Okolna Street 2, 50-422 Wroclaw (Poland)
  4. Institute for Problems of Materials Sciences, Academy of Sciences of Ukraine, Krzhyzhanovsky Street 3, 03680 Kiev (Ukraine)
Publication Date:
OSTI Identifier:
20951409
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 18; Other Information: DOI: 10.1103/PhysRevB.75.184102; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ASYMMETRY; BORON; BORON 11; ELECTRIC FIELDS; MAGNETIC FIELDS; MHZ RANGE 100-1000; MONOCRYSTALS; NUCLEAR MAGNETIC RESONANCE; POWDERS; TEMPERATURE RANGE 0273-0400 K; TENSORS; YTTRIUM COMPOUNDS

Citation Formats

Fojud, Z., Jurga, S., Herzig, P., Zogal, O. J., Pietraszko, A., Dukhnenko, A., and Shitsevalova, N. Electric-field-gradient tensor and boron site-resolved {sup 11}B NMR in single-crystalline YB{sub 12}. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.184102.
Fojud, Z., Jurga, S., Herzig, P., Zogal, O. J., Pietraszko, A., Dukhnenko, A., & Shitsevalova, N. Electric-field-gradient tensor and boron site-resolved {sup 11}B NMR in single-crystalline YB{sub 12}. United States. doi:10.1103/PHYSREVB.75.184102.
Fojud, Z., Jurga, S., Herzig, P., Zogal, O. J., Pietraszko, A., Dukhnenko, A., and Shitsevalova, N. Tue . "Electric-field-gradient tensor and boron site-resolved {sup 11}B NMR in single-crystalline YB{sub 12}". United States. doi:10.1103/PHYSREVB.75.184102.
@article{osti_20951409,
title = {Electric-field-gradient tensor and boron site-resolved {sup 11}B NMR in single-crystalline YB{sub 12}},
author = {Fojud, Z. and Jurga, S. and Herzig, P. and Zogal, O. J. and Pietraszko, A. and Dukhnenko, A. and Shitsevalova, N.},
abstractNote = {{sup 11}B NMR measurements on a single crystal of YB{sub 12} have been performed at room temperature at a frequency of 128.4 MHz. The electric-field-gradient (EFG) tensor components and the principal axes calculated previously by first-principles methods have been verified experimentally. Three magnetically different boron-atom groups in the B{sub 12} cluster were clearly observed for the crystal orientation used in this work. This distinction results from different EFG-tensor orientations with respect to magnetic field and not from different quadrupolar splittings ({nu}{sub Q}) or asymmetry-parameter values ({eta}). The magnetically different boron atoms have been identified through the calculated angle dependence of the satellite transitions (0 deg. -360 deg.). Very satisfactory agreement between the calculated and experimental angular dependencies of the EFG tensor has been obtained. Similarly, the quadrupolar splittings and asymmetry parameters agree very well with those previously determined from NMR measurements on a powder sample of YB{sub 12}.},
doi = {10.1103/PHYSREVB.75.184102},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 18,
volume = 75,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}
  • The syntheses of two new fluorooxoborates, Li{sub 2}B{sub 3}O{sub 4}F{sub 3} and Li{sub 2}B{sub 6}O{sub 9}F{sub 2}, which possess considerable ion conductivity at higher temperatures, have been reported recently. Here, we describe the characterisation of these compounds by solid-state {sup 11}B NMR spectroscopy. The complex central-transition MAS spectra, resulting from overlap of sub-spectra contributed by the individual boron species in the crystal structures, could be clearly separated by acquisition and analysis of 3QMAS spectra. By numerical fit of these sub-spectra, the isotropic chemical shift {delta}{sub iso}, the quadrupolar coupling constant {chi}, and the asymmetry {eta} were determined. Using known relationsmore » between boron coordination and chemical shift as well as quadrupolar coupling, the individual {sup 11}B NMR resonances have been ascribed to boron species in tetrahedral or trigonal environment. To remove remaining assignment ambiguities, the response of the {sup 11}B resonances to {sup 19}F decoupling was qualitatively analysed. Thus, by using the combined information conveyed by chemical shift, quadrupolar and dipolar interaction, a complete assignment of the complex {sup 11}B line shapes exhibited by the fluorooxoborates has been achieved. - Graphical abstract: Structure and solid-state {sup 11}B NMR spectrum of Li{sub 2}B{sub 3}O{sub 4}F{sub 3}. Highlights: Black-Right-Pointing-Pointer Characterisation of title compounds by solid-state {sup 11}B NMR spectroscopy. Black-Right-Pointing-Pointer Sub-spectra of boron species separated by evaluation of 3QMAS spectra. Black-Right-Pointing-Pointer Isotropic chemical shift and quadrupolar interaction parameters determined. Black-Right-Pointing-Pointer Full boron assignment based on NMR parameters and response to {sup 19}F decoupling.« less
  • Steady state nuclear magnetic resonance was performed in powdered (CH/sub 3/)/sub 4/NB/sub 3/H/sub 8/. The quadrupole coupling e/sup 2/qQ/2h of boron-11 decreases montonically at a decreasing rate from 70 kHz at 278 K to 16 kHz at 370 K. The birefringence also decreases with increasing temperature in the same temperature range and becomes undetectable at 473 K. We conclude that the B/sub 3/H/sub 8//sup -/ anions are undergoing large angle wobbling motion in this phase between 270 and 473 K. The wobbling amplitude gradually increases with temperature until the motion becomes isotropic at an order--disorder phase transition near 473 K.
  • The quaternary intermetallic compound superconductor YNi{sub 2}B{sub 2}C with transition temperature {ital T}{sub {ital c}}=15.5 K has been investigated by {sup 11}B and {sup 89}Y nuclear magnetic resonance (NMR) and by magnetic susceptibility {chi} measurements both in the normal and the superconducting states. The NMR and relaxation measurements have been performed in a powder sample and single crystals. {sup 11}B ({ital I}=3/2) NMR spectra display patterns typical for an axially symmetric field gradient with quadrupole coupling frequency {ital v}{sub {ital Q}}=698{plus_minus}1 kHz and {sup 89}Y ({ital I}=1/2) data show spectra typical for a large anisotropic Knight shift, {ital K}, withmore » axial symmetry (3{ital K}{sub ax}=0.042{percent}). In the normal state, the {sup 11}B {ital K} increases with decreasing temperature while {sup 89}Y {ital K} decreases. The temperature dependences of both the isotropic ({ital K}{sub iso}) and anisotropic (3{ital K}{sub ax}) components of the {sup 11}B and {sup 89}Y Knight shifts are presented together with dc magnetic susceptibility ({chi}) measurements obtained from magnetization measurements and are explained by the sharp features of the density of states near the Fermi level in the system. The analysis of the NMR and {chi}({ital T}) data when combined with the theoretical calculation of the Van Vleck contribution to {chi}({ital T}) allows the determination of the hyperfine coupling constants for both nuclei investigated and permits the separation of the different contributions to the total measured {chi}({ital T}). The nuclear spin-lattice relaxation rate (NSLR) ({ital T}{sup {minus}1}{sub 1}) results for {sup 11}B show an enhancement of ({ital T}{sub 1}{ital T}){sup {minus}1} when lowering the temperature, consistent with previous results. (Abstract Truncated)« less