Spin Dynamics in Ferrimagnets

Kab-Jin Kim, Korea Advanced Institute of Science and Technology

January 15, 2021

Antiferromagnetic spintronics is an emerging research field which aims to utilize antiferromagnets as core elements in spintronic devices. A central motivation toward this direction is that antiferromagnetic spin dynamics is expected to be much faster than ferromagnetic counterpart because antiferromagnets have much higher resonance frequencies than ferromagnets. However, experimental investigations of antiferromagnetic spin dynamics have remained unexplored mainly because of the immunity of antiferromagnets to magnetic fields. In this talk, we show that the antiferromagnetic spin dynamics can be realized in ferrimagnets. Using rare-earth–3d-transition metal ferrimagnetic compounds where total magnetic moment as well as angular momentum can be controlled by composition or temperature variation, we demonstrated that the antiferromagnetic domain wall dynamics can be achieved [1]. In addition, we also demonstrated the antiferromagnetic spin waves in ferrimagnets by probing the distinct handedness of spin wave across the compensation points [2]. If time allows, I will also discuss our recent findings about the spin transfer torque and magnetic damping of ferrimagnets [3,4]. Our finding highlights the importance of tuning of the compensation points of ferrimagnets, which could be a key towards antiferromagnetic spintronics.

[1] Kab-Jin Kim et al., Nat. Mater. 16, 1187 (2017).

[2] Changsoo Kim et al., Nat. Mater. 19, 980 (2020).

[3] Takaya Okuno et al., Nat. Electron. 2, 389 (2019).

[4] Duck-Ho Kim et al., Phys. Rev. Lett. 122, 127203 (2019).