Tailoring the chiral magnetic interaction between two individual atoms

Abstract

Chiral magnets are a promising route towards dense magnetic storage technology due to their inherent nano-scale dimensions and energy efficient properties. Engineering chiral magnets requires atomic-level control of the magnetic exchange interactions, including the Dzyaloshinskii–Moriya interaction, which defines a rotational sense for the magnetization of two coupled magnetic moments. Here we show that the indirect conduction electron-mediated Dzyaloshinskii–Moriya interaction between two individual magnetic atoms on a metallic surface can be manipulated by changing the interatomic distance with the tip of a scanning tunnelling microscope. We quantify this interaction by comparing our measurements to a quantum magnetic model and ab-initio calculations yielding a map of the chiral ground states of pairs of atoms depending on the interatomic separation. The map enables tailoring the chirality of the magnetization in dilute atomic-scale magnets.

Chiral magnetism of magnetic adatoms generated by Rashba electrons

“…distance, which was recently confirmed experimentally usingscanning tunneling microscopy (STM) and theoretically usingabinitio simulations based on density functional theory [8]. We note that today, besides theory, state-of-the-art STM experiments can be used to learn about the magnitude, oscillatory behavior and decay ofRKKY interactions, as demonstrated in  [28][29][30].…”

“…We also derive an appealing connection between the isotropic exchange interaction and the Dzyaloshinskii-Moriya interaction, which relates the latter to the first-order change of the former with respect tospin-orbit coupling. This implies that the chirality defined by the direction of the Dzyaloshinskii-Moriya vector is driven by the variation of the isotropic exchange interaction due to the spin-orbit interaction.distance, which was recently confirmed experimentally usingscanning tunneling microscopy (STM) and theoretically usingabinitio simulations based on density functional theory [8]. We note that today, besides theory, state-of-the-art STM experiments can be used to learn about the magnitude, oscillatory behavior and decay ofRKKY interactions, as demonstrated in  [28][29][30].Our goal is to address the DM interaction in an analytically tractable model and investigate its magnitude, sign and direction following a bottom-up approach, assembling nanostructures of different sizes and shapes, atom-by-atom.…”

Interface-induced phenomena in magnetism

“…If the DM interaction is strong enough relative to other interactions, it can lead to chiral ground state structures for the magnetization, including spiral states and skyrmion lattice states. Experimental evidence of significant interfacial DM interactions has been deduced from such ground state magnetic configurations in bilayer and trilayer systems such as Mn/W(110), Fe/Ir(111), Pd/Fe/Ir(111) [Bode et al ., 2007; von Bergmann et al ., 2014] and in pairs of individual Fe adatoms on Pt(111) surface via low-temperature inelastic scanning tunnelling spectroscopy [Khajetoorians et al ., 2016]. Even when not strong enough to influence the ground state magnetization configuration, the DM interaction can be strong enough to affect the spin wave dispersion [Udvardi and Szunyogh, 2009; Costa et al ., 2010] seen as an asymmetry in the energies of forward and backward moving spin waves, which can be measured via spin-polarized electron energy loss spectroscopy [Zakeri et al ., 2010] or Brillouin Light Scattering [Cho et al ., 2015; Di et al ., 2015; Nembach et al ., 2015].…”

Superadiabatic quantum heat engine with a multiferroic working medium

“…Ref. (29) and references therein). The spin excitation in this case is also captured by the low-energy effective model (1) with appropriately chosen parameters and fields.…”