Unconventional dynamics of ferrimagnets in the vicinity of compensation points*

Ferrimagnets have recently emerged as versatile platforms for spintronics owing to their unique tunability of material parameters. In particular, they offer the independent control of the spin density and the magnetization, which are impossible to achieve in more conventional magnets such as ferromagnets and antiferromagnets and thereby offer unprecedented opportunity to discover novel spin physics and realize highly tunable spintronic devices. In this talk, we will discuss the recent theoretical progress on the ensuing novel dynamics of ferrimagnets. The topics will include the dynamics of topological solitons such as domain walls [1,2], skyrmions [3,4], and vortices [5] within the framework of the generalized Landau-Lifshitz-Gilbert-like equations for ferrimagnets. Also, the novel properties of spin waves in ferrimagnets based on two distinct handedness will be discussed [6,7]. The talk will be concluded by providing a future outlook on ferrimagnetic spintronics and by discussing some fundamental questions that we are facing to understand the non-equilibrium properties of ferrimagnets [8].

[1] K-J. Kim et al., Nat. Mater. 16, 1187 (2017)
[2] S-H. Oh et al., Phys. Rev. B 96, 100407(R) (2017)
[3] S. K. Kim, K.-J. Lee, and Y. Tserkovnyak, Phys. Rev. B 95, 140404(R) (2017)
[4] Y. Hirata et al., Nat. Nanotechnol. 14, 232 (2019)
[5] S. K. Kim and Y. Tserkovnyak, Appl. Phys. Lett. 111, 032401 (2017)
[6] C. Kim, S. Lee, H.-G. Kim et al., Nat. Mater. 19, 980 (2020)
[7] S. K. Kim, K. Nakata, D. Loss et al., Phys. Rev. Lett. 122, 057204 (2019)
[8] T. Okuno, D.-H. Kim, S.-H. Oh et al., Nat. Electron. 2, 389 (2019)