Using the Fe-57m(3+) Mossbauer probe to determine the EFG tensor parameters at CuO cation sites

Mossbauer emission spectroscopy of the Co-57(Fe-57m) isotope has shown that the impurity iron atoms appearing at the CuO-lattice cation sites after th e decay of Co-57(2+) are donors and can become stabilized in two charge sta tes, Fe-57m(3+) and Fe-57m(2+), and that the population ratio of these stat es depends on the Fermi level, whose position is governed by native CuO-lat tice defects. A satisfactory agreement between the calculated and experimen tal values of the quadrupole splitting in Mossbauer spectra has been obtain ed for the Fe-57m(3+) centers. This permits one to consider the results obt ained in the Co-57(Fe-57m) Mossbauer emission spectroscopy study of cuprate s as reliable experimental data on the crystal-field EFG tensor parameters at copper sites. (C) 1999 American Institute of Physics. [S1063-7834(99)010 08-4].