Indirect chiral exchange through Dzyaloshinskii-Moriya–enhanced RKKY interactions in 1D transition metal oxides on fcc(100) surfaces

Seminar

  • Datum: 19.03.2019
  • Uhrzeit: 11:00
  • Vortragender: Prof. Dr. Matthias Bode
  • University Würzburg, Faculty of Physics and Astronomy
  • Ort: Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Saale)
  • Raum: Lecture Hall, B.1.11
 Indirect chiral exchange through Dzyaloshinskii-Moriya–enhanced RKKY interactions in 1D transition metal oxides on fcc(100) surfaces

Localized electron spins can couple magnetically via the indirect Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction even if their wave functions lack any substantial direct overlap. Theory predicts that spin-orbit scattering leads to a Dzyaloshinskii-Moriya (DM) type enhancement of the RKKY interaction, or DME-RKKY in short, giving rise to chiral exchange terms [1,2]. However, experimental evidence of this DME-RKKY interaction is sparse and essentially limited to non-collinear spin structures observed in surface-deposited clusters.

In my talk I will present spin-polarized scanning tunneling microscopy (SP-STM) investigations of transition metal oxides (TMO) on Ir(100) and Pt(100) which form self-organized chains with a local (3×1) superstructure and have recently been proposed as one-dimensional magnetic model systems [3,4]. As predicted theoretically [3], an antiferromagnetic coupling is observed for some oxides along the chains. In addition, we find that the inter-chain coupling across the non-magnetic fcc(001) substrate can vary between collinear and chiral. In the latter case the rotation angle between adjacent TMO chains depends on the particular substrate material. DFT calculations reveal that the DM interaction results in spin spirals with a periodicity in agreement with experiment.

[1] D.A. Smith, “New mechanisms for magnetic anisotropy in localised s-state moment materials,” J. Magn. Magn. Mater. 1, 214 (1976).

[2] A. Fert and P.M. Levy, “Role of anisotropic exchange interactions in determining the prop- erties of spin-glasses,” Phys. Rev. Lett. 44, 1538 (1980).

[3] P. Ferstl, L. Hammer, C. Sobel, M. Gubo, K. Heinz, M. A. Schneider, F. Mittendorfer, and J. Redinger, “Self-organized growth, structure, and magnetism of monatomic transition-metal oxide chains,” Phys. Rev. Lett. 117, 046101 (2016).

[4] P. Ferstl, T. Schmitt, M. A. Schneider, L. Hammer, A. Michl, and S. Müller, „Structure and ordering of oxygen on unreconstructed Ir(100)“, Phys. Rev. B 93, 235406 (2016).

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