  57Fe site Mossbauer Spectroscopy (MS) was used to investigate a dynamics of
57Fe atoms embedded into chromium lattice as impurities. From the Mossbauer
spectra recorded in the temperature range of 80 to 350 K, a temperature
dependence of the Lamb-Mossbauer factor, f, was determined. The latter revealed
an unusual dynamics of 57Fe atoms viz. harmonic mode below T = 145 K with a
characteristic effective Debye temperature, Qeff = 185 K and anharmonic one
above T o 145 K. The latter mode exists in two clearly separated temperature
intervals with slightly different Qeff - values viz. (i) 156 K for 145 K < T <
240 K and the record-high anharmonic coefficient e = 18 * 10-4 K-1 and (ii) 152
K for T > 240 K and e = 13.6 * 10-4 K-1. Based on the Visscher's theory, the
record-low values of relative binding force constants for Fe atoms were
determined as 0.0945, 0.0673 and 0.0634, respectively. It is suggested that the
unusual dynamics observed in this study might be related to the underlying
spin- and charge- and strain-density waves of chromium.

Materials Science;Other Condensed Matter