Complex magnetism of Mn-based Pnma ternary alloys: Three exchange interactions induced by the position of Mn atoms

•A link between the magnetism and Mn–Mn–Mn bond angle was built in MMnX alloys.•It is found that the exchange interaction translates with the bond angle.•Providing a novel avenue of designing multi-functional MMnX materials.

Density functional theory was used to study the relationship between magnetism and structure of Mn-based Pnma ternary alloys (MMnX). The magnetic states in these alloys largely rely on the value of Mn–Mn–Mn bond angle. There were two apparent critical bond angles being formed among ferromagnetic double exchange, anti-ferromagnetic super-exchange, and ferromagnetic super-exchange. Results indicated that the magnetic exchange interaction showed continuous transition in MMnX. The magnetism of MMnX was found to function on the basis of the relationship between bond angle and magnetic exchange interaction. This work provides a novel way of designing multi-functional materials made of MMnX with pointed magnetic exchange interaction.