[Nanomagnet Patterning on Epitaxially Grown Thin Films]
01/2023 ~ present
We are exploring multiple methods to pattern poly/single-crystalline nanomagnets ( < 200 nm).
[Strong Coupling of Magnon-Phonon System]
04/2021 ~ present
The dynamics of collective spin waves (magnons) observed in nanostructured magnets (nanomagnets) has been extensively studied in a variety of fields, including ultra-high density data storage, spin-transfer torque (STT) MRAM, all-optical switching, magnetic sensors, and other spintronic devices. When magnetic materials are structured on the nanometer scale, intriguing phenomena can be observed. Due to their nanoscale size, lattice vibrations (phonons) are quantized as opposed to their counterparts in infinite films, and their frequency is determined by the geometry of the nanomagnets much like the resonances of a drum’s vibrations. In these nanomagnets, the interplay between magnons and phonons starts to play an important role; these two quanta can be coupled via magnetoelastic properties of magnetostrictive materials. By controlling such magnetoelastic coupling, new, energy-efficient devices in the fields of straintronics, magnetic sensors and future computing can be designed. The focus of my research is to advance our fundamental understanding of this new quantum system and to maximize the effect with a view towards next-generation applications.
- Highlights
2022 Joint MMM-Intermag Conference, New Orleans, LA, USA, Winner of the Best Student Presentation Award in 2022 Joint MMM-Intermag Conference
“Ultrafast magneto-optical measurements for probing magnon–phonon interactions in nanomagnets”
Nature Reviews Physics 4, 288 (2022)
Sujung Kim
Acknowledgement to my advisor, professor Holger Schmidt for his helpful contribution to the manuscript.
(DOI: https://doi.org/10.1038/s42254-022-00457-z)
[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!
