Special Solid State Seminar - Changmin Lee, Lawrence Berkeley National Lab - “Exploring the dynamics of magnetic order and its excitations using magneto-optics”

Meeting ID: 964 8903 3854

Password:  190475

 

Harnessing spin degrees of freedom is one of the central goals of condensed matter physics and materials science. Toward this objective, I will present examples of dynamic magneto-optic experiments that provide novel perspectives toward understanding and controlling the complexities of magnetically ordered systems.

In the first example, I will discuss spatially-resolved ac Kerr effect microscopy measurements that identify the “hidden” phase that coexists with ferromagnetism in Co₃Sn₂S_2, a material widely considered to be a topological Weyl semimetal. I will demonstrate that the crossover to this “hidden” phase is a manifestation of a local 2D phase transition occurring within the domain wall, in which the magnetization texture changes from continuous rotation to unidirectional variation.

Next, I will present time-resolved optical measurements of spin wavepacket propagation in the Kagome ferromagnet Fe₃Sn₂. I will show that spin information can travel significantly faster than the group velocity of ballistic wavepackets, as a consequence of the unique interaction of light with the magnetostatic modes in Fe₃Sn₂. Effects related to this unusual spin wave “precursor” may have far-reaching consequences toward realizing long-range, ultrafast spin wave transport in both ferromagnetic and antiferromagnetic systems.