Structure peculiarities of cementite and their influence on the magnetic characteristics

TL;DR

This study uses first-principles density functional theory to analyze how the crystal structure of cementite affects its magnetic properties, explaining experimental coercivity behavior and suggesting Mossbauer spectroscopy as a detection method.

Contribution

It reveals the influence of carbon atom environment in cementite on its magnetic anisotropy and coercive force, providing insights into structure-property relationships.

Findings

Prismatic carbon environment has lowest energy and highest magnetic anisotropy.

Octahedral carbon environment increases coercive force after annealing.

Mossbauer spectroscopy can detect carbon environments in cementite.

Abstract

The iron carbide $Fe_3C$ is studied by the first-principle density functional theory. It is shown that the crystal structure with the carbon disposition in a prismatic environment has the lowest total energy and the highest energy of magnetic anisotropy as compared to the structure with carbon in an octahedron environment. This fact explains the behavior of the coercive force upon annealing of the plastically deformed samples. The appearance of carbon atoms in the octahedron environment can be revealed by Mossbauer experiment.