Stacking and layer dependence of magnetic properties in Ti2C and Fe2C

Magnetic MXenes are becoming an important family of materials for exploring 2D magnetism. However, investigations into the interdependence of layer thickness, stacking patterns and magnetism in these materials, from a microscopic point of view, are still lacking. In this work, we have used density functional theory based calculations to understand the effects of layer thickness and stacking on the magnetic properties in two magnetic MXenes, Ti2C and Fe2C, in their monolayer and bilayer forms. The ground-state magnetic structures, magnetic moments, magnetic exchange interactions, magnetic transition temperatures and magnetic anisotropy energies are calculated and analysed using their electronic structures and standardised models. We find that in both systems an increase in layer thickness (monolayer to bilayer) affects the ground-state magnetic configuration, which is driven by the changes in the magnetic exchange interactions. While the effects of the stacking pattern are rather weak in Ti2C, they are substantial, both qualitatively and quantitatively, in Fe2C. The computed results are analysed from their electronic structures. The results suggest that fascinating physical effects can be obtained in Fe2C by tuning the layer thickness and stacking patterns, making it more suitable for device applications.