What can one learn about Fe-Cr alloys using Mössbauer spectroscopy?

Applications of Mössbauer spectroscopy (MS) in the investigation of Fe-Cr alloys are reviewed. A high sensitivity of the hyperfine magnetic field to the presence of Cr atoms in the vicinity of the probe Fe atoms permits quantitative investigation of various aspects related both to the crystallographic as well as to the magnetic phase diagram of this alloy system. Concerning the former, presented is the relevance of MS for determining the borders of the miscibility gap and kinetics of the phase decomposition, distinguishing between nucleation and growth and spinodal decomposition, identifying the sigma-phase, and studying kinetics of its precipitation. Regarding the magnetic phase diagram, MS is useful for determining the Curie, the Néel, and the spin-freezing temperatures, hence studying paramagnetic→ferromagnetic, paramagnetic→antiferromagnetic and paramagnetic→spin-glass transitions. An effect of different heat treatments, strain, and irradiation with various particles on a distribution of Cr atoms in the Fe matrix is demonstrated, too. For α-FeCr alloys, relevance of MS for determining changes in spin and charge densities at Fe-sites induced by neighboring Cr atoms is illustrated, as well as its usefulness in studying changes caused by a high-temperature sulphidation and oxidation. Concerning properties of σ-FeCr alloys, the application of MS for determining the Curie and Debye temperatures is reviewed. Application of MS to study an effect of magnetism on the lattice dynamics of Fe atoms in σ-FeCr is also exemplified. Last but not least, issues pertinent to magnetic texture and mechanical alloying are addressed.