The formation and ordering of local magnetic moments in Fe-Al alloys

TL;DR

This paper uses density functional theory to analyze how local magnetic moments in Fe-Al alloys depend on composition and environment, revealing various magnetic states and explaining experimental superparamagnetic behavior.

Contribution

It provides a detailed theoretical study of magnetic states in Fe-Al alloys, including the role of local environment and temperature effects, which was not comprehensively addressed before.

Findings

Fe-Al alloys exhibit ferromagnetic, antiferromagnetic, and spin-spiral states.

Negative Fe moments are consistent with experimental observations.

Superparamagnetic behavior above 150 K explained by magnetic cluster percolation.

Abstract

With density functional theory, studied are the local magnetic moments in Fe-Al alloys depending on concentration and Fe nearest environment. At zero temperature, the system can be in different states: ferromagnetic, antiferromagnetic and spin-spiral waves (SSW) which has a minimum energy. Both SSW and negative moment of Fe atoms with many Al atoms around them agree with experiments. Magnetization curves taken from literature are analysed. Assumption on percolation character of size distribution of magnetic clusters describes well the experimental superparamagnetic behaviour above 150 K.