LAUSR

Significance Wavepackets of magnetization in magnetically ordered materials have emerged as a potential means to shuttle quantum information over large distances. A particularly promising platform is quasi-two-dimensional magnets in which the spins within each atomic plane are parallel but interplane order can be ferromagnetic or antiferromagnetic. In this work, we use ultrashort light pulses to generate spin wavepackets in a kagome-layered ferromagnet and to follow their subsequent motion. A significant result is that the arrival of magnetization at a remote location occurs in a time far shorter than expected from the spin wave velocity. We show that this “precursor” originates from the long-range magnetic dipole interaction. Related effects may have far-reaching consequences toward realizing long-range transport of spin information.