An atomic scale study of defects in Co₂FeAl

Area of Science:

• Materials Science
• Solid State Physics
• Magnetism

Background:

• Cobalt-Iron-Aluminum (Co2FeAl) is a complex magnetic alloy with potential applications in spintronics.
• Understanding local structure and magnetic properties is crucial for optimizing material performance.
• Defects and disorder significantly influence the magnetic behavior of such intermetallic compounds.

Purpose of the Study:

• To investigate the impact of defects on local structure and magnetic properties at Fe sites in Co2FeAl.
• To gain a comprehensive understanding of defect types and disordering in Co2FeAl under non-equilibrium conditions.
• To correlate findings with theoretical predictions and experimental observations of spin polarization.

Main Methods:

• Detailed analysis using 57Fe Mössbauer spectroscopy.
• Systematic correlation of spectroscopic results with material treatments.
• Investigation of local atomic environments and magnetic interactions.

Main Results:

• Quantified the extent of A2 type disordering, with up to 35% of Fe atoms affected.
• Provided a fundamental understanding for the experimentally observed lower spin polarization compared to theoretical values.
• Revealed a linear correlation between valence electron concentration and effective magnetic hyperfine fields at different Fe occupation sites.

Conclusions:

• The study elucidates the role of defects and disorder in Co2FeAl, particularly the prevalence of A2 disordering.
• Findings explain discrepancies between theoretical and experimental spin polarization values.
• Established a relationship between electronic structure and magnetic hyperfine fields in Co2FeAl.