Debye temperature of disordered bcc-Fe-Cr alloys

TL;DR

This study measures the Debye temperature of disordered Fe-Cr alloys across various compositions, revealing non-monotonous behavior linked to magnetic properties and atomic interactions, with implications for understanding alloy dynamics.

Contribution

It provides the first detailed compositional dependence of Debye temperature in Fe-Cr alloys using Mossbauer spectroscopy, highlighting correlations with magnetic and structural features.

Findings

Debye temperature shows non-monotonous variation with composition.

Local maxima and minima in Debye temperature correlate with magnetic properties.

Harmonic force constant significantly decreases in highly chromium-rich alloys.

Abstract

Debye temperature, TD, of Fe100-xCrx disordered alloys with 0<x<99.9 was determined from the temperature dependence of the centre shift of 57Fe Mossbauer spectra recorded in the temperature range of 80-300K. Its compositional dependence shows an interesting non-monotonous behaviour. For 0<x<~45 as well as for ~75<x<~95 the Debye temperature is enhanced relative to its value of a metallic iron, and at x=~3 there is a local maximum having a relative height of ~12% compared to a pure iron. For ~45<x<~75 and for x>~95 the Debye temperature is smaller than the one for the metallic iron, with a local minimum at x=~55 at which the relative decrease of TD amounts to ~12%. The first maximum coincides quite well with that found for the spin-waves stiffness coefficient, D0, while the pretty steep decrease observed for x>~95 which is indicative of a decoupling of the probe Fe atoms from the underlying chromium matrix is likely related to the spin-density waves which constitute the magnetic structure of chromium in that interval of composition. The harmonic force constant calculated from the Debye temperature of the least Fe-concentrated alloy (x>99.9) amounts to only 23% of the one characteristic of a pure chromium.