Nanoscale chemical segregation to twin interfaces in ?-MnAl-C and resulting effects on the magnetic properties

In this study, aberration-corrected scanning transmission electron microscopy coupled with electron energy-loss spectroscopy (STEM-EELS) was used to investigate the atomistic structure and chemical com-position of true twin and order twin boundaries in ferromagnetic r-MnAl-C. True twins and order twins were distinguished based on the diffraction patterns using TEM. No elemental segregation was observed at the coherent true twin boundary but some Mn enrichment within a region of about 1.5-2 nm was found at the incoherent true twin boundary. A transition region with Mn enrichment about 4-6 nm wide was found at the order twin boundary. A carbon cluster with a size of around 5 nm was also found at the twin boundary. Micromagnetic simulations were conducted to study the effect of this chemical seg-regation at twin interfaces on the magnetic properties. The results showed that the coercivity tends to increase with increasing structural and chemical disorder at the interface. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

In this study, aberration-corrected scanning transmission electron microscopy coupled with electron energy-loss spectroscopy was used to investigate the atomistic structure and chemical composition of twin boundaries in ferromagnetic r-MnAl-C. The results showed that there was Mn enrichment at both coherent and incoherent twin boundaries, and a transition region with Mn enrichment was found at order twin boundaries. Micromagnetic simulations revealed that increasing structural and chemical disorder at the interface led to an increase in coercivity.