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Coupling of Coexisting Noncollinear Spin States in the Fe Monolayer on Re(0001) - Alexandra Palacios - Vendredi 17 février 2017 à 11 h

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Alexandra Palacios - Post-doc à Karlsruhe dans le groupe du Prof. Wiesendanger


Recently, there has been increasing interest in non-collinear magnetic states in ultrathin films and several complex spin textures have been reported [1]. Typically such non-collinear spin configurations arise due to competing interactions, for instance nearest neighbor and next-nearest neighbor Heisenberg exchange, which can lead to spin spirals with a period given by the ratio of the interaction strengths. The magnetic interactions of a thin-film system are governed by the distance and the number of nearest neighbors, by the adsorption geometry, and the hybridization with the non-magnetic substrate. For Fe thin films it has been demonstrated that not only different substrates [2-3] but also a different stacking, uniaxial strain relief, or different symmetry of a surface can lead to a variety of magnetic ground states [1, 4-5]. This suggests that different non-collinear magnetic ground states may coexist, giving rise to the question about mutual interactions between them. Here, we report on spin-polarized scanning tunneling microscopy (SP-STM) measurements of an Fe monolayer on Re(0001). In addition to the previously observed Néel state in the pseudomorphic hcp-stacked Fe monolayer [6], we find a spin spiral state in dislocation lines that are incorporated to release lateral strain. A close analysis reveals that within a dislocation line the spins are canted with respect to the dislocation line propagation. At the interface between these two coexisting non-collinear magnetic states we find a sharp transition on the order of a few atoms only. In addition, a spatial correlation between the spin spiral and the Néel state suggests a coupling between the two states, which is confirmed by Monte-Carlo simulations [7]

References :

[1] K. von Bergmann, A. Kubetzka, O. Pietzsch and R. Wiesendanger, J. Phys. : Condens. Matter, 26, 394002 (2014).

[2] B. Hardrat, A. Al-Zubi, P. Ferriani, S. Blügel, G. Bihlmayer and S. Heinze, Phys. Rev. B, 79, 094411 (2009).

[3] E. Simon, K. Palotas, B. Ujfalussy, A. Dek, G. M. Stocks and L. Szunyogh, Journal of Physics : Condensed Matter, 26, 186001 (2014).

[4] A. Kubetzka, P. Ferriani, M. Bode, S. Heinze, G. Bihlmayer, K. von Bergmann, O. Pietzsch, S. Blüge and R. Wiesendanger, Phys. Rev. Lett., 94, 087204 (2005).

[5] P.-J. Hsu, A. Finco, L. Schmidt, A. Kubetzka, K. von Bergmann and R. Wiesendanger, Phys. Rev. Lett., 116, 017201 (2016).

[6] S. Ouazi, A. Kubetzka, K. von Bergmann and R. Wiesendanger, Phys. Rev. Lett., 112, 076102 (2014).

[7] A. Palacio-Morales, A. Kubetzka, K. von Bergmann and R. Wiesendanger, arxiv:1605.05158 (2016).