Understanding the Noncollinear Antiferromagnetic IrMn₃ Surfaces and Their Exchange-Biased Heterostructures from First-Principles

We provide a complete and systematic first-principles study of the thermodynamic stability, structural parameters, and magnetic properties of the T1 noncollinear antiferromagnetic L1 2 -IrMn 3 surface and the L1 2 -IrMn 3 /Fe heterostructure. Furthermore, we investigate the exchange bias (EB) effect in the heterostructure and describe its previously unknown complex magnetic coupling at the interface. We consider four atomic configurations and four magnetic arrangements, finding two stable terminations for the surface and the heterostructure, which are in good agreement with experimental high-resolution transmission electron microscopy data. Using a comparative approach to analyze the heterostructure’s EB properties, we discover that the number of Mn–Fe interactions is related to the EB intensity. This finding could lead to EB tailoring methods by controlling the termination of the layers. Finally, we are able to accurately describe the interface magnetic coupling atom-by-atom, and we find a relationship between the interface antiferromagnetic order and heterostructure stability. Our analysis provides a possible mechanism for the appearance of EB in noncollinear/collinear heterostructures and is in good agreement with experimental hysteresis measurements of the IrMn 3 /Fe system.