Imaging the coupling between itinerant electrons and localised moments in the centrosymmetric skyrmion magnet GdRu2Si2

Abstract

Magnetic skyrmions were thought to be stabilised only in inversion-symmetry breaking structures, but skyrmion lattices were recently discovered in inversion symmetric Gd-based compounds, spurring questions of the stabilisation mechanism. A natural consequence of a recent theoretical proposal, a coupling between itinerant electrons and localised magnetic moments, is that the skyrmions are amenable to detection using even non-magnetic probes such as spectroscopic-imaging scanning tunnelling microscopy (SI-STM). Here SI-STM observations of GdRu2Si2 reveal patterns in the local density of states that indeed vary with the underlying magnetic structures. These patterns are qualitatively reproduced by model calculations which assume exchange coupling between itinerant electrons and localised moments. These findings provide a clue to understand the skyrmion formation mechanism in GdRu2Si2.

Mechanism of antisymmetric spin polarization in centrosymmetric multiple-$Q$ magnets based on bilinear and biquadratic spin cross products

“…For example, it is possible to obtain information about a way of superposing the spin density waves by detecting the spin-dependent electronic band structure based on spinand angle-resolved photoemission spectroscopy. Such an indirect identification of the magnetic textures through electric probes like the spectroscopic imaging scanning tunneling microscopy measurement and the noncolinear magnetoresistance has been performed in magnetic materials with complicated magnetic textures [91,[104][105][106]. The observation of the momentum-dependent antisymmetric spin polarization would be also useful to understand the nature of the multiple-Q states in both real and momentum spaces.…”

“…( 3) and ( 4) can be straightforwardly applied to complex noncollinear and noncoplanar spin configurations. As an example, we apply the derived expressions to the multiple-Q states observed in the f -electron compound GdRu 2 Si 2 [90,91]. The crystal structure of this compound is the centrosymmetric tetragonal crystal structure.…”

Recent Progress in Exploring the Magnetic Solids with Room‐Temperature Skyrmionic Spin Configurations

“…[9] Recently, skyrmions were also found in the rare-earth magnets; the Ruderman-Kittel-Kasuya-Yosida (RKKY) contributed to the formation of skyrmions. [28][29][30][31][32] Magnetic skyrmions are expected to become an emerging information carrier that affords the advantages of small size, high stability, high density, and low energy consumption. In recent years, the application of skyrmion science has expanded gradually.…”

Multiple skyrmion crystal phases by itinerant frustration in centrosymmetric tetragonal magnets

“…[1][2][3][4] Depending on a way of superposing helices, various topological spin textures, such as a magnetic skyrmion, vortex, meron, and hedgehog, are realized. [5][6][7][8][9][10] Notably, such multiple-Q orderings have been ubiquitously found in both noncentrosymmetric [11][12][13][14][15][16][17][18][19][20][21] and centrosymmetric [22][23][24][25][26][27][28][29][30] magnets composed of p, d, and f electrons, although their mechanisms are qualitatively different: The former relies on the Dzyaloshinskii-Moriya (DM) interaction 31,32) and the latter is accounted for by frustrated exchange interactions [33][34][35][36][37][38][39] and/or effective magnetic interactions mediated by itinerant electrons. [40][41][42][43][44][45][46] Their different mechanisms lead to a difference...…”

“…This parameter set of (γ 1 , γ 2 , γ 3 ) well reproduces the experimental observations of the SkX and the other multiple-Q states in a skyrmion-hosting material GdRu 2 Si 2 . 28) The other model parameters (γ 4 , γ 6 ) are chosen to realize the situation with the competing interactions in momentum space as γ 4 /γ 1 = γ 6 /γ 3 = 0.9 satisfying χ Q1 > χ Q3 . The following results are, at least, qualitatively similar to 0.8 γ 4 /γ 1 , γ 6 /γ 3 < 1.…”