Anomalous binding of Fe atoms in chromium
Abstract
Binding of 57Fe atoms in a metallic chromium was investigated in a Cr-Fe alloy, containing less than 0.1 at% Fe enriched to ~95 % in 57Fe isotope, using 57Fe-site Mossbauer spectroscopy. The binding force was derived from the Debye temperature, TD, that, in turn, was calculated from the temperature dependence of the central shift of the Mossbauer spectra recorded in the range of 80 to 330 K. Following a temperature dependence of the line width that shows a minimum at ~155 K, two temperature intervals were considered: a low temperature one (LT) ranging from 80 to 155 K, and the TD - value of 292 (12) K or 279 (34) K, and a high temperature one (HT) ranging from 155 to 330 K with the TD - value of 399 (15) or 399 (25) K, depending on the fitting procedure. The corresponding values of the harmonic force (spring) constant are: 35.4 N/m and 66.1 N/m or 33.8 N/m and 66.1 N/m for the LT and HT, respectively. This means that in the HT range the binding force of 57Fe atoms by the Cr matrix is by a factor of ~1.9 - 2 stronger than that in the LT range. This anomaly is possibly related with a different polarization of the spin-density waves in the LT and HT "phases".