Park Pyeongjae, Park Kisoo, Kim Taehun, Kousaka Yusuke, Lee Ki Hoon, Perring T G, Jeong Jaehong, Stuhr Uwe, Akimitsu Jun, Kenzelmann Michel, Park Je-Geun
Center for Quantum Materials, Seoul National University, Seoul 08826, Republic of Korea.
Center for Correlated Electron Systems, Institute for Basic Science, Seoul 08826, Republic of Korea.
Phys Rev Lett. 2020 Jul 10;125(2):027202. doi: 10.1103/PhysRevLett.125.027202.
Noncollinear magnetic order arises for various reasons in several magnetic systems and exhibits interesting spin dynamics. Despite its ubiquitous presence, little is known of how magnons, otherwise stable quasiparticles, decay in these systems, particularly in metallic magnets. Using inelastic neutron scattering, we examine the magnetic excitation spectra in a metallic noncollinear antiferromagnet CrB_{2}, in which Cr atoms form a triangular lattice and display incommensurate magnetic order. Our data show intrinsic magnon damping and continuumlike excitations that cannot be explained by linear spin wave theory. The intrinsic magnon linewidth Γ(q,E_{q}) shows very unusual momentum dependence, which our analysis shows to originate from the combination of two-magnon decay and the Stoner continuum. By comparing the theoretical predictions with the experiments, we identify where in the momentum and energy space one of the two factors becomes more dominant. Our work constitutes a rare comprehensive study of the spin dynamics in metallic noncollinear antiferromagnets. It reveals, for the first time, definite experimental evidence of the higher-order effects in metallic antiferromagnets.
非共线磁序在多个磁系统中因各种原因出现，并展现出有趣的自旋动力学。尽管其普遍存在，但对于磁振子（一种原本稳定的准粒子）在这些系统中，尤其是在金属磁体中的衰减情况，人们了解甚少。利用非弹性中子散射，我们研究了金属非共线反铁磁体CrB₂中的磁激发光谱，其中Cr原子形成三角晶格并呈现非公度磁序。我们的数据显示了本征磁振子阻尼和类似连续体的激发，这无法用线性自旋波理论来解释。本征磁振子线宽Γ(q,E_q)表现出非常不寻常的动量依赖性，我们的分析表明这源于双磁振子衰变和斯托纳连续体的结合。通过将理论预测与实验进行比较，我们确定了在动量和能量空间中这两个因素之一何时变得更为主导。我们的工作构成了对金属非共线反铁磁体自旋动力学的罕见全面研究。它首次揭示了金属反铁磁体中高阶效应的确切实验证据。
