Dy160andEr166Mössbauer studies of concentrated and diluted rare-earth dihydrides: Single-line compounds and crystal-field effects

Abstract

Mössbauer-effect measurements on the cubic intermetallic rare-earth dihydrides are reported utilizing the 86.8-keV and the 80.6-keV $2^{+}$ →$0^{+}$ $\gamma$ transitions of ${}_{}{}^{160}{}_{}{}^{}\mathrm{Dy}$ and ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$, respectively. All studies were carried out at liquid-helium temperatures on pure and diluted (with Y or Sc) paramagnetic samples. It is found that in the more concentrated alloys spin-spin ($4f-4f$) relaxation rates at 4.2 K are sufficiently fast to allow for the use of these systems as narrow-single-line Mössbauer sources and absorbers. Measurements on highly dilute ${}_{}{}^{160}{}_{}{}^{}\mathrm{Dy}$ and ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ impurities in Y${\mathrm{H}}_2$ reveal the resolved paramagnetic hyperfine structure of a ${\Gamma }_7$ crystalline electric field (CEF) ground state in both cases. The results are discussed in terms of CEF theory.