Monte Carlo simulation results are reported on magnetic ordering in ABC stacked kagome layers with fcc symmetry for both $\mathit{XY}$ and Heisenberg models which include exchange interactions with the eight near neighbors. Well known degeneracies of the two-dimensional (2D) system persist in the 3D case and analysis of the numerical data provides strong evidence for a fluctuation-driven first-order transition to well-defined long-range order characterized as the layered $q=0$ (${120}^{\circ }$) spin structure. Effects of varying the interlayer coupling are also examined. The results are relevant to understanding the role of frustration in IrMn${}_3$ alloys widely used by the magnetic storage industry as thin films in the antiferromagnetic pinning layer in GMR and TMR spin valves. Despite the technological importance of this structure, it has not previously been noted that the magnetic Mn ions of fcc IrMn${}_3$ form kagome layers.

• Received 23 January 2012

DOI:https://doi.org/10.1103/PhysRevB.86.104419