Martin Plumer

Memorial University of Newfoundland
Magnetic Order in the FCC Kagome Lattice: Hard drives and basket weaving

Monte Carlo simulation and spin wave analysis results are presented which explore the magnetic order and phase transition in the FCC Kagome lattice [1]. This study is relevant to bulk IrMn3, various forms of which are used in thin films as the exchange bias antiferromagnet of choice in spin valves [2]. Despite the technological importance of this structure, it has not previously been noted that the magnetic Mn-ions of FCC IrMn3 reside on Kagome layers, ABC stacked along <111> axes normal to the film plane.  The 2D Kagome antiferromagnet has been of interest for many years due to the macroscopic degeneracy of its 1200 spin structure around vertex-sharing triangles, giving rise to exotic magnetic ordering for both quantum and classical statistics [3]. Simulations will be reported on the 3D FCC Kagomé 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 120-degree spin structure.  Effects of cubic anisotropy are shown to reduce the degeneracy and drive the phase transition to be continuous, consistent with of an analysis of spin wave modes. Preliminary MC simulation results of the magnetic field – temperature phase diagram, thin films with axial surface anisotropy, and a 2D system with only dipole interactions, will be briefly reviewed. 


 [1] V. Hemmati, M.L. Plumer, J.P. Whitehead, and B.W. Southern, Phys. Rev. B 86, 104419 (2012); M.D. Leblanc, M.L. Plumer, J.P. Whitehead, and B.W. Southern,  Phys. Rev. B 88, 094406 (2013); M.D. LeBlanc, B.W. Southern, M.L. Plumer and J.P. Whitehead, Phys. Rev. B 90, 144403 (2014). 

[2] M. Tsunoda et al, Appl. Phys. Lett. 97, 072501 (2010). 

[3] M.E. Zhitomirsky, Phys. Rev. B 78, 094423  (2008).

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