Surface effects on the magnetic structure and magnetocrystalline anisotropy of IrMn3 from first principles

IrMn3 is a key antiferromagnetic material for spintronic devices due to its very high magnetic anisotropy energy. Calculating this requires knowledge of magnetic ordering, which is experimentally challenging to resolve. We use first-principles density functional theory calculations with a novel spin initialisation method to investigate both the magnetic structure and magnetocrystalline anisotropy of IrMn3 surfaces and IrMn3/Fe interfaces. Our new method is based on the epikernel principle using point groups of atomic sites to determine an optimal initial spin configuration. Using this, we find that the Fe on Ir–Mn-[100] has two values of magnetic anisotropy energy depending on the choice of surface termination, and that the perpendicular magnetic anisotropy induced by the Ir–Mn-[111] surface is due to a mechanism that leads to relaxation of the magnetic frustration of the surface layer. These findings highlight the importance of atomic-scale details when designing spintronic devices.