On-line SPICE-SPIN+X Seminars

On-line Seminar: 16.03.2022 - 15:00 German Time

Ferrimagnetic Spintronics

Kyung-Jin Lee, KAIST

Compensated ferrimagnets combine the best features of antiferromagnets and ferromagnets [1]. Antiferromagnets are of considerable interest because the exchange torques between the two sublattices give a time scale that is much faster than that in ferromagnets and the lack of magnetization and net angular momentum lead to minimal perturbation by stray fields and eased constraints due to angular momentum conservation. A compensated ferrimagnet has all these virtues. At the same time, the lack of symmetry between the two sublattices in a compensated ferrimagnet means that quantities like average spin currents are not zero making the systems potentially easier to manipulate and detect the consequences. We will describe calculations and measurements of domain wall and skyrmion motion at the angular momentum compensation point. At this point with no net spin density, the rotational motion of the magnetic textures (domain walls and skyrmions) is absent. As a result, domain walls move fast [2,3], the skyrmion Hall effect vanishes [4], the magnon-photon coupling enhances [5], and a relativistic domain wall motion is realized [2,6]. We will also discuss the increased efficiency of spin torques due to the weakened dephasing in compensated ferrimagnets. Combining experiments with theoretical studies, Refs. [7] and [8] show large torques for ferrimagnetic multilayers and for ferrimagnetic domain walls, respectively.

[1] S. K. Kim, G. S. D. Beach, K.-J. Lee, T. Ono, Th. Rasing, and H. Yang, Ferrimagnetic spintronics, Nat. Mater. 21, 24 (2022).
[2] T. Shiino et al., Antiferromagnetic domain wall motion driven by spin-orbit torques. Phys. Rev. Lett. 117, 087203 (2016).
[3] K.-J. Kim et al., Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnets. Nat. Mater. 16, 1187 (2017).
[4] Y. Hirata et al., Vanishing skyrmion Hall effect at the angular momentum compensation temperature of a ferrimagnet. Nat. Nanotechnol. 14, 232 (2019).
[5] J. Shim, S.-J. Kim, S. K. Kim, and K.-J. Lee, Enhanced magnon-photon coupling at the angular momentum compensation point of ferrimagnets. Phys. Rev. Lett. 125, 027205 (2020).
[6] L. Caretta et al., Relativistic kinematics of a magnetic soliton. Science 370, 1438 (2020).
[7] J. Yu et al., Long spin coherence length and bulk-like spin-orbit torque in ferromagnetic multilayers. Nat. Mater. 18, 29 (2019).
[8] T. Okuno et al., Spin-transfer torques for domain wall motion in antiferromagnetically coupled ferrimagnets. Nat. Electron. 2, 372 (2019).

Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
PDF file of the talk available here