Quantitative analysis of atomic disorders in full-Heusler Co2FeSi alloy thin films using x-ray diffraction with Co-Ka and Cu-Ka sources

TL;DR

This paper introduces a novel XRD-based analysis method to quantitatively evaluate atomic disorders, including DO3, in full-Heusler Co2FeSi alloy thin films, revealing high ordering levels post-thermal treatment.

Contribution

A new XRD analysis technique capable of quantifying all atomic disorders in full-Heusler alloys, including previously unanalyzable DO3 disorder.

Findings

High site occupancy of Co, Fe, and Si atoms at 800°C RTA

Revealed temperature dependence of atomic disorder in Co2FeSi films

Confirmed high L21 structural order in RTA-formed films

Abstract

The authors developed a new analysis technique for atomic disorder structures in full-Heusler alloys using x-ray diffraction (XRD) with Co-Ka and Cu-Ka sources. The developed technique can quantitatively evaluate all the atomic disorders for the exchanges between X, Y, and Z atoms in full-Heusler X2YZ alloys. In particular, the technique can treat the DO3 disorder that cannot be analyzed by ordinary Cu-Ka XRD. By applying this technique to full-Heusler Co2FeSi alloy thin films formed by rapid thermal annealing (RTA), RTA-temperature (TA) dependence of the atomic disorders was revealed. The site occupancies of Co, Fe, and Si atoms on their original sites were 98 %, 90 %, and 93 %, respectively, for the film formed at TA = 800 degree C, indicating that the RTA-formed Co2FeSi film had the L21 structure with the extremely high degree of ordering.