2020/09/30 by Yongkang Luo, Shizeng Lin, M. Leroux +8
Physics and Astronomy · #cond-mat.str-el #cond-mat.mtrl-sci #cond-mat.supr-con
paper · pdf · doi:10.1038/s43246-020-00083-1
published as Communications Materials 1, 83 (2020) · 28 pages, 4+4 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:1711.08873
arxiv created 2020/11/12 · arxiv updated 2020/11/16
Magnetic skyrmions are well-suited for encoding information because they are nano-sized, topologically stable, and only require ultra-low critical current densities jc to depin from the underlying atomic lattice. Above jc skyrmions exhibit well-controlled motion, making them prime candidates for race-track memories. In thin films thermally-activated creep motion of isolated skyrmions was observed below jc as predicted by theory. Uncontrolled skyrmion motion is detrimental for race-track memories and is not fully understood. Notably, the creep of skyrmion lattices in bulk materials remains to be explored. Here we show using resonant ultrasound spectroscopy--a probe highly sensitive to the coupling between skyrmion and atomic lattices--that in the prototypical skyrmion lattice material MnSi depinning occurs at jc^* that is only 4 percent of jc. Our experiments are in excellent agreement with Anderson-Kim theory for creep and allow us to reveal a new dynamic regime at ultra-low current densities characterized by thermally-activated skyrmion-lattice-creep with important consequences for applications.