Cluster multipole dynamics in noncollinear antiferromagnets

A systematic framework to investigate the spin dynamics in a noncollinear antiferromagnet is proposed. Taking Mn3Sn as a representative example, we derive an effective low-energy model based on the multipole expansion of the magnetic structure, and investigate the uniform precession and the domain wall dynamics. We show that the solution for the effective model accurately reproduces the numerical calculation of the Landau-Lifshitz-Gilbert equations. Our results indicate that Mn3Sn has preferable properties for applications to a racetrack memory and a spin torque oscillator, and thus is a promising candidate for spintronics devices by using the multipole degrees of freedom.