Resonant elastic x-ray scattering from the skyrmion lattice inCu2OSeO3

Abstract

We report the study of the skyrmion state near the surface of Cu2OSeO3 using soft resonant elastic x-ray scattering (REXS) at the Cu L3 edge. Within the lateral sampling area of 200 × 200 µm 2 , we found a long-range-ordered skyrmion lattice phase as well as the formation of skyrmion domains via the multiple splitting of the diffraction spots. In a recent REXS study of the skyrmion phase of Cu2OSeO3 [Phys. Rev. Lett. 112, 167202 (2014)], Langner et al. reported the observation of the unexpected existence of two distinct skyrmion sublattices that arise from inequivalent Cu sites, and that the rotation and superposition of the two periodic structures leads to a moiré pattern. However, we find no energy splitting of the Cu peak in x-ray absorption measurements and, instead, discuss alternative origins of the peak splitting. In particular, we find that for magnetic field directions deviating from the major cubic axes, a multidomain skyrmion lattice state is obtained, which consistently explains the splitting of the magnetic spots into two-and more-peaks.

Reorientations, relaxations, metastabilities, and multidomains of skyrmion lattices

“…Besides this orientational preference, patterns with 12 or more peaks have been observed by SANS and resonant x-ray scattering on Cu 2 OSeO 3 [31][32][33][34]. These patterns indicate the coexistence of multiple skyrmion lattice domains with different orientations.…”

“…In MnSi one of the three helices preferentially aligns along the 110 crystallographic direction. For Cu 2 OSeO 3 this orientational preference is along 100 [12,31,32], although some SANS measurements seem to indicate that for specific fields and temperatures the 110 direction is preferred [11,33].…”

“…The occurrence of these multidomain states appears for bulk Cu 2 OSeO 3 to be related to the thermal history [33,38]. In addition, it was proposed that multidomains are stabilized by magnetic fields applied along directions deviating from the major cubic axes [31,32]. However, none of these previous studies provides a holistic view of the interrelation between the orientation of skyrmion lattices and the crystallographic lattice, the occurrence of multidomain lattices, and the influence of metastabilities induced by different magnetic field histories for all cubic chiral magnets.…”

Unconventional topological Hall effect in high-topological-number skyrmion crystals

“…Conventional magnetic skyrmions have Q = ±1, with the sign distinguishing skyrmions and antiskyrmions. By varying the whirling period ξ of the azimuthal angle of the local spin Φ, high-topologicalnumber skyrmions with Q > 1 are theoretically predicted [8][9][10][11] . When identical skymions form a spatially periodic array, we obtain a skyrmion crystal (SkX).…”

Ferromagnetic Resonance with Magnetic Phase Selectivity by Means of Resonant Elastic X-Ray Scattering on a Chiral Magnet

“…At intermediate magnetic field just below T c , a pocket of skyrmion lattice state is observed. The trigonal order of the spin whirls in the plane perpendicular to the field translates to the characteristic sixfold pattern of magnetic satellites in both small-angle neutron scattering [41][42][43][44][45] and REXS [26][27][28][29][30][31], as shown in Fig. 1(e).…”