Non-collinear spin states in bottom-up fabricated atomic chains

Manuel Steinbrecher,Khai Ton That,Jens Wiebe,Roman Rausch,Jan Hermenau,Alexander A. Khajetoorians,Michael Potthoff,Roland Wiesendanger

doi:10.1038/s41467-018-05364-5

Abstract

Non-collinear spin states with unique rotational sense, such as chiral spin-spirals, are recently heavily investigated because of advantages for future applications in spintronics and information technology and as potential hosts for Majorana Fermions when coupled to a superconductor. Tuning the properties of such spin states, e.g., the rotational period and sense, is a highly desirable yet difficult task. Here, we experimentally demonstrate the bottom-up assembly of a spin-spiral derived from a chain of iron atoms on a platinum substrate using the magnetic tip of a scanning tunneling microscope as a tool. We show that the spin-spiral is induced by the interplay of the Heisenberg and Dzyaloshinskii-Moriya components of the Ruderman-Kittel-Kasuya-Yosida interaction between the iron atoms. The relative strengths and signs of these two components can be adjusted by the interatomic iron distance, which enables tailoring of the rotational period and sense of the spin-spiral.

Highlights

Inversion asymmetry at the interface of the magnetic material and the substrate
While the usual Heisenberg interaction Jij ^Si Á ^Sj favors a parallel or antiparallel alignment of neighboring spins, the DM interaction favors perpendicular orientations. The interplay of these two interactions can induce a spin-spiral state, with a rotational sense determined by the orientation of Dij, and with a period given by the ratio of Dij and Jij, and by the magnetic anisotropy[10]
By comparison of the experimental results to densitymatrix renormalization group (DMRG) calculations, we demonstrate that the spin-spiral’s wavelength and rotational sense can be tuned via the interatomic distances of the Fe atoms in the chain

Summary

Introduction

While the usual Heisenberg interaction Jij ^Si Á ^Sj favors a parallel (ferromagnetic) or antiparallel (antiferromagnetic) alignment of neighboring spins, the DM interaction favors perpendicular orientations. The interplay of these two interactions can induce a spin-spiral state, with a rotational sense determined by the orientation of Dij, and with a period given by the ratio of Dij and Jij, and by the magnetic anisotropy[10]. Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between magnetic atoms in contact to metallic substrates contains a DM component leading to non-collinear order, which is typically strong for high-Z materials[23,24]. By comparison of the experimental results to densitymatrix renormalization group (DMRG) calculations, we demonstrate that the spin-spiral’s wavelength and rotational sense can be tuned via the interatomic distances of the Fe atoms in the chain

Methods

Results

Conclusion