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 ${\mathrm{CrB}}_2$, 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 $\mathrm{\Gamma }(\mathbf{q},E_{\mathbf{q}})$ 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.

中文翻译：

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金属非共线三角形反铁磁体CrB_ {2}中动量相关的磁振子寿命。

非共线磁阶在多种磁系统中由于各种原因而出现，并表现出有趣的自旋动力学。尽管存在无处不在，但对于这些系统中的强磁子（否则是稳定的准粒子）如何衰减（鲜为人知），特别是在金属磁体中，衰减率知之甚少。使用非弹性中子散射，我们检查了金属非共线反铁磁体中的磁激发光谱${铬}_2$，其中Cr原子形成一个三角形晶格，并显示出不相称的磁序。我们的数据显示了固有的磁振子阻尼和类似连续谱的激励，这不能用线性自旋波理论来解释。本征磁振子线宽$\mathrm{\Gamma }（\mathbf{q}，{Ë}_{\mathbf{q}}）$表现出非常不寻常的动量依赖性，我们的分析表明这是由于两个马格诺衰变和斯托纳连续体的结合所致。通过将理论预测与实验进行比较，我们确定了两个因素之一在动量和能量空间中的哪个位置更占主导地位。我们的工作对金属非共线反铁磁体的自旋动力学进行了罕见的全面研究。它首次揭示了金属反铁磁体中高阶效应的明确实验证据。