Monte Carlo simulations of the fcc Kagom\'{e} lattice

For many years, Ir-Mn alloys have been widely used by the magnetic storage industry in thin-film form as the antiferromagnetic pinning layer in GMR and TMR spin valves [1]. Despite the technological importance of this structure, it has not previously been noted that the magnetic Mn-ions of fcc IrMn$_3$ reside on Kagom\'{e} layers ABC stacked along $<$111$>$ axes normal to the film plane [2,3]. Results of Monte Carlo simulations will be reported on the bulk fcc Kagom\'{e} lattice for both XY and Heisenberg models including the eight NN exchange interactions. Degeneracies persist in the 3D case and there is strong evidence for a fluctuation-driven first-order transition to well-defined long-range order characterized as the layered ``$q$=0'' 120-degree spin structure. Effects of varying the inter-layer coupling are also examined. \\[4pt] [1] M. Tsunoda et al, Appl. Phys. Lett. {\bf 97}, 072501 (2010).\\[0pt] [2] I. Tomeno et al, J. Appl. Phys. {\bf 86}, 3853 (1999).\\[0pt] [3] L. Szunyogh et al, Phys. Rev. B {\bf 79}, 020403(R) (2009).