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Effective bilinear-biquadratic model for noncoplanar ordering in itinerant magnets
| Title: | Effective bilinear-biquadratic model for noncoplanar ordering in itinerant magnets |
| Authors: | Hayami, Satoru Browse this author | | Ozawa, Ryo Browse this author | | Motome, Yukitoshi Browse this author |
| Issue Date: | 20-Jun-2017 |
| Publisher: | American Physical Society (APS) |
| Journal Title: | Physical Review B |
| Volume: | 95 |
| Issue: | 22 |
| Start Page: | 224424-1 |
| End Page: | 224424-20 |
| Publisher DOI: | 10.1103/PhysRevB.95.224424 |
| Abstract: | Noncollinear and noncoplanar magnetic textures including Skyrmions and vortices act as emergent electromagnetic fields and give rise to novel electronic and transport properties. We here report a unified understanding of noncoplanar magnetic orderings emergent from the spin-charge coupling in itinerant magnets. The mechanism has its roots in effective multiple spin interactions beyond the conventional Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism, which are ubiquitously generated in itinerant electron systems with local magnetic moments. By carefully examining the higher-order perturbations in terms of the spin-charge coupling, we construct a minimal effective spin model composed of the bilinear and biquadratic interactions with particular wave numbers dictated by the Fermi surface. Taking two-dimensional systems as examples, we find that our effective model captures the underlying physics of the instability toward noncoplanar multiple-Q states discovered recently: a single-Q helical state expected from the RKKY theory is replaced by a double-Q vortex crystal with chirality density waves even for an infinitely small spin-charge coupling on generic lattices [R. Ozawa et al., J. Phys. Soc. Jpn. 85, 103703 (2016)], and a triple-QSkyrmion crystal with a high topological number of two appears while increasing the spin-charge coupling on a triangular lattice [R. Ozawa, S. Hayami, and Y. Motome, Phys. Rev. Lett. 118, 147205 (2017)]. We find that by introducing an external magnetic field, our effective model exhibits a plethora of multiple-Q states. Our effective model will serve as a guide for exploring further exotic magnetic orderings in itinerant magnets, not only in two dimensions but also in three dimensions. |
| Rights: | ©2017 American Physical Society |
| Type: | article |
| URI: | http://hdl.handle.net/2115/67007 |
| Appears in Collections: | 理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 速水 賢
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