An atomic scale study of defects in Co2FeAl.

Changes in the local structure and magnetic properties at Fe sites due to defects were addressed in a detailed manner in Co2FeAl by 57Fe Mössbauer spectroscopy. Based on the systematic correlation of these results a comprehensive understanding of the defects and hence of the different types of disordering that occur in Co2FeAl subjected to different non-equilibrium treatments have been obtained in this study. As high as 35% of the Fe atoms were deduced to be associated with the A2 type of disordering in Co2FeAl, which provides a basic understanding of the observed much lower value of spin polarization as observed in this system against the high value predicted theoretically. Also this study revealed a striking linear correlation between the valence electron concentration and the effective magnetic hyperfine fields as deduced at different sites of occupation of 57Fe atoms.