Damping effects form the core of many emerging concepts for high-speed spintronic applications. Important characteristics such as device switching times and magnetic domain-wall velocities depend critically on the damping rate. While the implications of spin damping for relaxation processes are intensively studied, damping effects during impulsive spin excitations are assumed to be negligible because of the shortness of the excitation process. Herein we show that, unlike in ferromagnets, ultrafast damping plays a crucial role in antiferromagnets because of their strongly elliptical spin precession. In time-resolved measurements, we find that ultrafast damping results in an immediate spin canting along the short precession axis. The interplay between antiferromagnetic exchange and magnetic anisotropy amplifies this canting by several orders of magnitude towards large-amplitude modulations of the antiferromagnetic order parameter. This leverage effect discloses a highly efficient route towards the ultrafast manipulation of magnetism in antiferromagnetic spintronics.

阻尼效应构成了高速自旋电子应用中许多新兴概念的核心。诸如设备切换时间和磁畴壁速度之类的重要特性关键取决于阻尼率。尽管深入研究了自旋阻尼对弛豫过程的影响，但由于激励过程的短暂性，脉冲自旋激发过程中的阻尼效应被认为是微不足道的。本文中，我们显示出，与铁磁体不同，超快阻尼在反铁磁体中起着至关重要的作用，因为它们具有强烈的椭圆自旋进动。在时间分辨的测量中，我们发现超快阻尼导致沿短进动轴的立即旋转倾斜。反铁磁交换与磁各向异性之间的相互作用将这种倾斜放大了几个数量级，朝着反铁磁阶数参数的大幅度调制。这种杠杆作用揭示了一种高效的方法，可在反铁磁自旋电子学中超快地操纵磁场。