[Strong Coupling of Magnon-Phonon System]
04/2021 ~ 08/2024
Hybrid magnonic systems are promising platforms for quantum technologies, leveraging coherent coupling between magnons and phonons. Here, we demonstrate strong magnon–phonon coupling in CoFe nanomagnets, a material with high magnetostriction. Using time-resolved magneto-optical Kerr effect spectroscopy, we demonstrate strong coupling between magnonic and phononic modes in both polycrystalline and single-crystalline CoFe nanomagnets. Our findings reveal strong coupling with cooperativity values of for a polycrystalline CoFe nanomagnet and for a single-crystalline CoFe nanomagnet. The enhanced coupling strength in the single-crystalline CoFe nanomagnet is attributed to the higher magnetostriction in CoFe systems and lower intrinsic magnetic damping. This work highlights the critical role of material properties and crystalline structures in optimizing hybrid magnon–phonon systems for miniaturized quantum applications.
- Highlights
[4] “Engineering strong magnon–phonon coupling in single CoFe nanomagnets”
Journal of Applied Physics 137, 123904 (2025)
Sujung Kim, Becker Sharif, Scott Dhuey, Thomas David Yuzvinsky, Weigang Yang, David Lederman, and Holger Schmidt
[3] “Magnetoelastic Control of Nanomagnet Dynamics”
Sujung Kim and Holger Schmidt
in “Dynamical Phenomena in Spintronics/Nanomagnetics”, edited by Anjan Barman and Supriyo Bandyopadhyay
[2] “Ultrafast magneto-optical measurements for probing magnon–phonon interactions in nanomagnets”
Nature Reviews Physics 4, 288 (2022)
Sujung Kim
[1] 2022 Joint MMM-Intermag Conference, New Orleans, LA, USA, Winner of the Best Student Presentation Award in 2022 Joint MMM-Intermag Conference.
[Nanomagnet Patterning on Epitaxially Grown Thin Films]
01/2023 ~ 08/2024
We developed a sacrificial-layer method to pattern poly/single-crystalline nanomagnets ( < 200 nm) that are MgO and CoFe compatible using Citric-acid-based etchant.
- Highlights
“Engineering strong magnon–phonon coupling in single CoFe nanomagnets”
Journal of Applied Physics 137, 123904 (2025)
Sujung Kim, Becker Sharif, Scott Dhuey, Thomas David Yuzvinsky, Weigang Yang, David Lederman, and Holger Schmidt
[Magnetization Dynamics of Epitaxially Grown Thin Films]
06/2022 ~ 12/2022
- Highlights
“Magnetization dynamics of CoFe/Co2MnSi magnetic bilayer structure”
Journal of Applied Physics (2023)
Sujung Kim, Yawen Guo, Weigang Yang, Toyanath Joshi, David Lederman, and Holger Schmidt
This paper is part of the Special Topic on Recent Advances in Magnonics.
[Half-Metallic Heusler Alloy and CoFe-based Magnetic Tunnel Junction]
04/2022 ~ 12/2022 (half time, project with Magtera Inc.)
We developed a patterning process to fabricate Heusler Alloy and CoFe based MTJs, and we worked on the optical and electrical characterization.
[Dual-Beam All-Optical Magnetization Switching for Spintronic Applications]
09/2018 ~ 03/2021
When a magnetic thin film is excited by femtosecond pulse laser, exchange couplings in electron, phonon and spin are involved during the process of switching of magnetization. It is the fastest dynamics available so far, which occurs on a picosecond timescale!
My research consists of setup construction, Helicity-Dependent All-Optical-Switching (HD-AOS) experiments, and modeling and simulations.
I constructed Dual-Beam HD-AOS setup from scratch (initially with a senior grad student), demonstrated an additional degree of freedom to manipulate the final magnetization state, and numerically implemented the parameter into the switching probability using M3TM (I simplified my sample for the initial demonstration purpose).
The proposed additional degree of freedom extends the current understanding of the fastest dynamics and provides a new method of controlling magnetization in more energy-efficient manner. In this regard, the aforementioned research certainly extend the boundaries of potential applications using HD-AOS in future technologies including spintronic devices and neuromorphic computing. The impact of this study on future technology can be immense.
I am open to collaborations including but not limited to thin-film sample fabrications, spintronic device fabrications.
[Building a Dual-Beam All-Optical Magnetization Switching Setup]
09/2018 ~ 03/2021
We built the Dual-Beam All-Optical-Switching setup at UCSC (built together with Dr. Mike Jaris).
Writing/Erasing Setup
Imaging Setup
[Cross-section of Twisted GeS Plates]
The video was created by combining cross-sectional SEM images that are sequentially acquired in the course of FIB milling of a mesoscale GeS structure along its twist axis.
[Sample Transfer via HF solution method]
Twisted GeS Plates were transferred via HF solution method for studying their twist structure.
[Some Photoshop Efforts for Twisted GeS]
It was definitely fun and exciting to work on this beautiful and unreal structure! I truly loved my baby samples and these images show how much I loved them!
