Skyrmion phase and competing magnetic orders on a breathing kagomé lattice.

Hirschberger, Max; Nakajima, Taro; Gao, Shang; Peng, Licong; Kikkawa, Akiko; Kurumaji, Takashi; Kriener, Markus; Yamasaki, Yuichi et al. · Nat Commun · 2019

basic_science · Level V

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Abstract

Magnetic skyrmion textures are realized mainly in non-centrosymmetric, e.g. chiral or polar, magnets. Extending the field to centrosymmetric bulk materials is a rewarding challenge, where the released helicity/vorticity degree of freedom and higher skyrmion density result in intriguing new properties and enhanced functionality. We report here on the experimental observation of a skyrmion lattice (SkL) phase with large topological Hall effect and an incommensurate helical pitch as small as 2.8 nm in metallic Gd<sub>3</sub>Ru<sub>4</sub>Al<sub>12</sub>, which materializes a breathing kagomé lattice of Gadolinium moments. The magnetic structure of several ordered phases, including the SkL, is determined by resonant x-ray diffraction as well as small angle neutron scattering. The SkL and helical phases are also observed directly using Lorentz-transmission electron microscopy. Among several competing phases, the SkL is promoted over a low-temperature transverse conical state by thermal fluctuations in an intermediate range of magnetic fields.