Monte Carlo simulations of the fcc kagome lattice: Competition between triangular frustration and cubic anisotropy

The impact of local cubic anisotropy on the magnetic states of the Heisenberg model on the fcc kagome lattice are examined through classical Monte Carlo simulations. Previous simulations revealed that the macroscopic degeneracy of the two-dimensional (2D) kagome exchange-coupled co-planar spin system partially persists in the 3D case of ABC stacked layers giving rise to a discontinuous phase transition. Local cubic anisotropy is shown to remove this degeneracy by re-orienting the spins out of the co-planar configuration. In addition, the re-oriented states are shown to carry a uniform magnetic moment. Simulation results indicate that the effect of anisotropy is to transform the first-order phase transition to a continuous one. These results are relevant to Ir-Mn alloys which have been widely used by the magnetic storage industry in thin-film form as the antiferromagnetic pinning layer in spin valves.