Determination of polaron hopping frequency limits in modified vanadate and lithium borovanadate glass systems from EPR line-narrowing

POSTER

Abstract

Electron Paramagnetic Resonance (EPR) spectra of four different vanadate glass systems of varying molar ratios, R, show that the hyperfine structure lines (hfs) become more resolved and defined as R increases. For example, in the sodium oxide vanadate glass system, RNa2OV2O5, low R-values (around 0.1) result in little to no hyperfine resolution in the EPR spectra. However, as the R-value increases and approaches 0.5, the spectra significantly become more resolved, and a dramatic narrowing of the lines occurs, revealing a hyperfine coupling parameter B of order 17.7 mT, corresponding to an upper-limit polaron hopping frequency of 487 $\pm $ 20 MHz. In the model proposed here, this narrowing is due to an increase in hopping time for polarons associated with V4+ ions. By similar analyses, the systems of RCaOV2O5, RBaOV2O5, and RLi2OV2O5 exhibit comparable polaron hopping frequency limits of 480 $\pm $ 20 MHz, 469 $\pm $ 20 MHz, and 468 $\pm $ 20 MHz, respectively, when R is near 1.0. Data taken at various temperatures ranging from room temperature to 4.2 K reveal that EPR spectra linewidths are not dependent upon temperature.

Authors

  • J. McKnight

    William Jewell College

  • K. Whitmore

    William Jewell College

  • P. Bunton

    William Jewell College

  • Steve Feller

    Coe College

  • Michael Turner

    Illinois Institute of Technology, Bettendorf High School, Bettendorf, IA, Mississippi Bend Area Education Agency, Bettendorf, IA, Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA, Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA, Max-Planck-Institut fuer Mikrostrukturphysik, Halle, Germany, CNRS, Universite Lyon I, France, Freie Universitaet Berlin, Germany, University of Jyvaskila, Finaland, Iowa State University/Ames Laboratory, Materials Science Division, Argonne National Laboratory and Department of Chemistry, Northwestern University, Materials Science Division, Argonne National Laboratory, Advanced Photon Source, Argonne National Laboratory, Ames Laboratory and Iowa State University, Indiana University, Illinois State University, University of Iowa, Louisiana State University, University of Warwick, Rutherford Appleton Laboratory, Coe College, University of Northern Iowa, Iowa State University and Ames Laboratory, University of Illinois, Ames Laboratory, University of Florida, Tulane University, The Department of Physics and The James Franck Institute, The University of Chicago, J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS 66506, Department of Physics, Augustana College, Sioux Falls, SD 57197, Intense Laser Physics Theory Unit, Illinois State University, Argonne National Laboratory, Dr, Drake University, Physics Department, Ocean University of China, Qingdao, Physics Department, Southern Illinois University Carbondale, Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA, Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA, NEST-CNR-INFM and Scuola Normale Superiore, I-56126 Pisa, Italy, University of New Hampshire Department of Physics, University of Chicago

  • B. Baker

    William Jewell College