Band Structure Engineering to Optimize Spin-Wave Propagation in Weyl ferromagnet Co<sub>2</sub>MnGa<sub>1-</sub> <sub>x</sub>Ge<sub>x</sub>.

Wang, Jinlong; Zhang, Yao; Hu, Junfeng; Song, He; Sun, Xiaozhen; Meng, Xiangrui; Xu, Ziyue; Yin, Yuefeng et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Spin waves, the quantized excitations of magnetic order, have been widely explored as low-power information carriers in conventional metallic systems (e.g., NiFe) and insulating materials like yttrium iron garnet (YIG). Recently, magnetic Weyl semimetals (WSMs) have emerged as a novel platform for magnonics, leveraging their unique band structures, strong spin-orbit interactions, and fertile topological behavior. Despite this potential, spin-wave dynamics in magnetic WSMs remain largely uncharted. In this work, this gap is addressed by investigating spin-wave propagation in epitaxial Co<sub>2</sub>MnGa<sub>1-</sub> <sub>x</sub>Ge<sub>x</sub> (0 ≤ x ≤ 1) thin films, a prototypical magnetic WSMs system. By changing the ratio between Ga and Ge, how band-structure engineering, specifically tuning the Fermi level into the minority-spin pseudogap is demonstrated, systematically modulates the electronic and magnetic properties to achieve ultralow Gilbert damping (≈1.5 × 10<sup>-3</sup>) alongside long spin-wave decay lengths over 100 µm. These results establish a generalizable strategy for optimizing spin-wave media while unlocking a materials platform to probe intertwined charge, spin and orbit, with profound implications for next-generation spintronic and magnonic technologies.