Chicago Section

Zoom Link: https://argonne.zoomgov.com/j/1617260288?p wd=Z3kzMkI4L0QzS2ZzZ0VvOUorL1lCQT09

Speaker: Professor Kab-Jin Kim

Department of Physics,

KAIST, Daejeon 34141, Republic of Korea

Date: Thursday, March 21, 2024
Time: 11:00 AM CDT

Abstract

Magnetic solitons, such as magnetic domain walls, skyrmions, vortices, and Bloch lines, represent distinctive spin configurations within magnets and play a crucial role in modern magnetism and spintronics [1]. Investigating the dynamics of these solitons is pivotal, as it not only unveils new physics [2,3] but also propels the development of magnetic devices [4,5]. Concurrently, spin transport is another essential facet of spintronics research. Efforts to generate pure spin currents have spurred investigations into various spin orbit effects, including the spin Hall effect and Rashba effect, leading to intriguing physical phenomena and diverse magnetoresistances [6].

In this presentation, I will share insights from my journey in spintronics research, focusing on uncovering novel phenomena in spin dynamics and transport. The first part focuses on spin dynamics across a broad dynamic range, particularly emphasizing research on magnetic domain wall dynamics. Discussions encompass the creep and hopping dynamics governing slow regimes [7] and extend to the fast and ultrafast dynamics achievable in emerging magnetic materials, such as ferrimagnets and antiferromagnets [8]. In the second part, I will present our recent findings on spin transport phenomena. We employed THz time-domain spectroscopy to reveal the fundamental magnetotransport characteristics in magnetic materials undergoing phase transitions [9,10]. Additionally, we will demonstrate how the utilization of magnetic phase transitions can lead to the generation of large spin current bursts, the underlying mechanism of which transcends the orthodox spin torque theory [11]. If time permits, I will introduce our recent results on magnonic studies, covering topics such as the control of magnon handedness in ferrimagnets [12], gate-controlled coherent magnon frequency modulation [13], magnetic-field manipulation of thermal phonons via magnon-phonon coupling [14], and nonlinear magnon-magnon coupling in synthetic antiferromagnets [15].

[1] H.B. Braun, Adv. Phys., 61, 1 (2012)
[2] I.M. Miron et al., Nature, 476, 189 (2011); L. Liu et al., Science, 336, 555 (2012);
[3] S. Emori et al., Nat. Mater., 12, 611 (2013); K.-S. Ryu et al., Nat. Nanotech., 8, 527 (2013)
[4] S. Parkin et al., Nat. Nanotech., 10, 195 (2015)
[5] Z. Luo et al., Nature, 579, 214 (2020)
[6] A. Manchon et al., Rev. Mod. Phys., 91, 035004 (2019)
[7] K.-J. Kim et al., Nature, 458, 740 (2009); J.-C. Lee et al., Phys. Rev. Lett., 107, 067201 (2012); M. Song et al., Adv. Mater., 34, 2203275 (2022)
[8] Y. Yoshimura et al., Nat. Phys. 7, 157 (2016); K.-J. Kim et al., Nat. Mater. 16, 1187 (2017)
[9] J.-H. Park et al., Sci. Rep. 11, 20884 (2021) 
[10] J.-H. Park et al., “Unraveling the origin of conductivity change in FeRh phase transitions”, In preparation
[11] T. Lee et al., “observation of longitudinal spin pumping”, under review
[12] C. Kim et al., Nat. Mater. 19, 980 (2020)
[13] J.-G. Choi et al., Nat. Comm. 13, 3783 (2022)
[14] G.-H. Lee et al., “Magnetic Control of Phonon Transport in Magnetic Insulator Thulium Iron Garnet”, In preparation
[15] M. You et al., “Nonlinear magnonic interaction in a synthetic antiferromagnet”, In preparation

Biography:

Prof. Kab-Jin Kim is an Associate Professor in the Department of Physics at KAIST in South Korea. He earned his BA and Ph.D. degrees from Seoul National University before joining KAIST in 2016, following 5.5 years of post-doctoral and assistant professorial work at Kyoto University. His research focuses on experimental studies in spintronics, particularly in magnetic domain wall dynamics and their applications. With over 108 published papers, his current interests lie in investigating spin dynamics and transport in extended material systems, encompassing ferrimagnets and antiferromagnets. Additionally, Prof. Kim is an author of a widely-received book for general audiences and a sought-after public speaker, with his lectures, including those on YouTube, collectively amassing over 10 million views.

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