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Debye temperature of disordered bcc-Fe-Cr alloys
Authors: S.M. Dubiel, J. Cieslak, B.F.O. Costa
Ref.: J. Phys.:Cond Matter 22, 55402-55408 (2010)
Abstract: The Debye temperature, Theta(D), of Fe(100-x)Cr(x) disordered alloys with 0 <= x <= 99.9 was determined from the temperature dependence of the centre shift of (57)Fe Mossbauer spectra recorded in the temperature range of 60-300 K. Its compositional dependence shows an interesting non-monotonous behaviour. For 0 < x <= similar to 45, as well as for similar to 75 <= x <= similar to 95, the Debye temperature is enhanced relative to its value of a metallic iron, and at x approximate to 3 there is a local maximum having a relative height of similar to 12% compared to a pure iron. For similar to 45 <= x <= similar to 75 and for x >= similar to 95 the Debye temperature is smaller than the one for the metallic iron, with a local minimum at x approximate to 55 at which the relative decrease of Theta(D) amounts to similar to 12%. The first maximum coincides quite well with that found for the spin-waves stiffness coefficient, Do, while the pretty steep decrease observed for x >= similar to 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 and show also anomalous dynamic behaviour. The harmonic force constant calculated from the effective Debye temperature of the least Fe-concentrated alloy (x >= 99.9) amounts to only 23% of the one characteristic of a pure chromium as determined from the heat capacity experiment.
