Lattice-Dynamical Properties ofFe57Impurity Atoms in Pt, Pd, and Cu from Precision Measurements of Mössbauer Fractions

Precision measurements of the Mössbauer fractions of ${\mathrm{Fe}}^{57}$ in single crystals of Cu, Pd, and Pt were obtained over a range from liquid-helium temperatures to around 750°K in about 50°K intervals, using the "black wide absorber" technique. The over-all accuracy is estimated to be better than 0.7%, with a somewhat larger error for Pt. Our data are consistent with a harmonic lattice with small cubic and quartic anharmonic contributions. Properly weighted Debye temperatures ${\Theta }_D\mathrm{}(-1\mathrm{})\mathrm{}$ and ${\Theta }_D\mathrm{}(-2\mathrm{})\mathrm{}$ were derived from the low- and high-temperature limits of our $f$ measurements, which were compared with equivalent data for the pure hosts. We conclude that Fe in Cu is about 20% more strongly bound than Cu in Cu, while Fe in Pd and Pt shows about a 20% weaker average force constant than the host atoms. Fe in Cu also has a much larger degree of anharmonicity than pure Cu. Analysis of earlier data on Fe in Ni shows a similar behavior. Our data were also examined for evidence of localized impurity modes. The low-temperature data for Fe in Pt are consistent with the existence of a predicted localized mode, but they do not provide unambiguous evidence.