New insights into defects and magnetic interactions inducing lattice disordering in Co₂Fe_0.5Cr_0.5Al

Atomic scale understanding of defect induced magnetic interactions resulting in lattice disordering has been deduced in a detailed manner for the first time in Co₂Fe_0.5Cr_0.5Al based on Mössbauer spectroscopic studies and compared with the results obtained in Co₂Fe_0.8Cr_0.2Al and Co₂FeAl. An interesting linear correlation between valence electron concentration and the mean hyperfine fields at Fe sites in Co₂FeAl based compounds has been deduced which is observed to exhibit different slopes with the substitution of Cr. This study elucidates an important role of the manifestation of the magnetic interactions especially between Fe, Co and Cr atoms leading to significant changes in the concentration and specific types of defects selectively produced in Co₂Fe_0.5Cr_0.5Al as compared with that of Co₂Fe_0.8Cr_0.2Al subjected to similar non-equilibrium treatments in this study. Further, for the first time this study elucidates the striking correlation of the effective value of the hyperfine field with the degree of ordering/disordering of the lattice with the Fe atoms associated with ordered sites experiencing a much higher value of the hyperfine field as compared to that of the disordered sites. This study also proposes optimal annealing treatment for the recovery of defects in Co₂Fe_0.5Cr_0.5Al, which would be of significant importance in these spintronic materials.