Magnetic order in the ultrathin iron film on the Ir(001) surface

Abstract:
There are many important features which distinguish magnetic overlayers from conventional magnetic materials. The reduced coordination on the surface induces geometry as well as chemical binding change, the substrate can strongly modify the magnetic state and properties of the overlayer system. Particularly suitable systems for detailed investigation are Fe overlayers on Ir(001) and Rh(001) surfaces.

We present detailed ab initio study of structural and magnetic stability of a Fe monolayer on the fcc(001) surface of iridium extending our last investigation [1]. The Fe monolayer has a strong tendency to order antiferromagnetically for the true relaxed geometry. We compare the influence of two adsorbate species on the magnetic ground state – H and O. We found that the adsorption of oxygen (contrary to the H) lowers the stability of antiferromagnetic order and prefers ferromagnetic ground state.

The ferromagnetism is stabilized by the increased Fe-Ir layer spacing. The present study centers around the evaluation of pair exchange interactions between Fe atoms in the Fe overlayer as a function of adsorbate coverage which allows for a detailed understanding of the antiferromagnetism of a Fe/Ir(001) overlayer. Our calculations indicate that the nature of the true ground state could be more complex and display a spin spiral like rather than a c(2x2)- antiferromagnetic order. A comparison with recent experimental data [2] will be also given.

[1] J. Kudrnovský, F. Máca, I. Turek, and J. Redinger, Phys. Rev. B 80, 064405 (2009).
[2] V. Martin et al., Phys. Rev. B 76, 205418 (2007).