https://scholar.dgist.ac.kr/handle/20.500.11750/39 2026-08-11T10:41:43Z 2026-08-11T10:41:43Z Kim, Bomin Jeong, Yunseong Baek, Wonjung Kim, Hobyeong Rhee, Taeseong Cho, Beopgil Choi, Woo-Jae Ha, Jae-Hyun Park, Jaemun Hong, Jung-Il Kwon, Yong Seung Seo, Jungpil Park, Keeseong https://scholar.dgist.ac.kr/handle/20.500.11750/60590 2026-08-03T06:40:16Z 2026-07-31T15:00:00Z

Title: A comparative synthesis study of α-MnTe across solid-state, Arc-melting, and Te-flux routes Author(s): Kim, Bomin; Jeong, Yunseong; Baek, Wonjung; Kim, Hobyeong; Rhee, Taeseong; Cho, Beopgil; Choi, Woo-Jae; Ha, Jae-Hyun; Park, Jaemun; Hong, Jung-Il; Kwon, Yong Seung; Seo, Jungpil; Park, Keeseong Abstract: Although alpha-MnTe has attracted renewed interest in both thermoelectric and altermagnetic contexts, direct comparisons of practically accessible synthesis routes within a common experimental framework remain limited. Here, we compare conventional solid-state reaction, arc melting and Te self-flux growth methods under a common framework of composition control and thermal history. Within the explored conditions, the phase outcome depends not only on the nominal starting composition but also on route-dependent synthesis environments, including volatilization in sealed ampoules, repeated remelting and rapid quenching in arc melting, and crystal-flux interfacial segregation in Te self-flux growth. In the solid-state route, slow heating with a slightly Mn-rich starting composition was associated with reduced MnTe2 and alpha-MnTe-dominant products. Arc melting yielded alpha-MnTe-dominant products without post-annealing, accompanied by dendritic-like microstructures. Te self-flux growth yielded single crystals, although a minor MnTe2-rich interfacial or surface layer often remained. While the present dataset does not define a rigorous phase boundary or a definitive mechanistic model, it provides a systematic comparative framework for route-dependent phase outcomes and impurity persistence in alpha-MnTe synthesis.

2026-07-31T15:00:00Z Kim, Bomin Jeong, Yunseong Baek, Wonjung Kim, Hobyeong Rhee, Taeseong Cho, Beopgil Choi, Woo-Jae Ha, Jae-Hyun Park, Jaemun Hong, Jung-Il Kwon, Yong Seung Seo, Jungpil Park, Keeseong https://scholar.dgist.ac.kr/handle/20.500.11750/60502 2026-07-24T02:10:19Z 2026-07-31T15:00:00Z

Title: A comparative synthesis study of α-MnTe across solid-state, Arc-melting, and Te-flux routes Author(s): Kim, Bomin; Jeong, Yunseong; Baek, Wonjung; Kim, Hobyeong; Rhee, Taeseong; Cho, Beopgil; Choi, Woo-Jae; Ha, Jae-Hyun; Park, Jaemun; Hong, Jung-Il; Kwon, Yong Seung; Seo, Jungpil; Park, Keeseong Abstract: Although alpha-MnTe has attracted renewed interest in both thermoelectric and altermagnetic contexts, direct comparisons of practically accessible synthesis routes within a common experimental framework remain limited. Here, we compare conventional solid-state reaction, arc melting and Te self-flux growth methods under a common framework of composition control and thermal history. Within the explored conditions, the phase outcome depends not only on the nominal starting composition but also on route-dependent synthesis environments, including volatilization in sealed ampoules, repeated remelting and rapid quenching in arc melting, and crystal-flux interfacial segregation in Te self-flux growth. In the solid-state route, slow heating with a slightly Mn-rich starting composition was associated with reduced MnTe2 and alpha-MnTe-dominant products. Arc melting yielded alpha-MnTe-dominant products without post-annealing, accompanied by dendritic-like microstructures. Te self-flux growth yielded single crystals, although a minor MnTe2-rich interfacial or surface layer often remained. While the present dataset does not define a rigorous phase boundary or a definitive mechanistic model, it provides a systematic comparative framework for route-dependent phase outcomes and impurity persistence in alpha-MnTe synthesis.

2026-07-31T15:00:00Z Ha, Jae-Hyun Cho, Beopgil Park, Jaemun Kim, Tae-Hwan Park, Keeseong Han, Dong-Soo Hong, Jung-Il https://scholar.dgist.ac.kr/handle/20.500.11750/60458 2026-07-21T01:10:15Z 2026-04-30T15:00:00Z

Title: Magnetic glass behaviors of bicontinuous nanocomposite films fabricated by partial oxidation of Pt-Ni-Co Author(s): Ha, Jae-Hyun; Cho, Beopgil; Park, Jaemun; Kim, Tae-Hwan; Park, Keeseong; Han, Dong-Soo; Hong, Jung-Il Abstract: We report the magnetic properties of metal/oxide hybrid nanocomposite thin films derived from an interpenetrating nanoscale morphology formed by reactive co-sputtering of Pt and Co0.7Ni0.3 in a controlled argon and oxygen atmosphere at room temperature. During deposition, selective oxidation of transition-metal elements of Co and Ni, in the presence of less reactive Pt, drives spontaneous phase separation into ferromagnetic (FM) metallic PtNi and antiferromagnetic (AFM) amorphous CoO nanophases. The resulting nanocomposite constitutes a highly entangled three-dimensional network of FM/AFM domains where characteristic dimensions remain in the order of approximately less than 2 nm. The resulting bicontinuous architecture facilitates dense interfacial spin couplings across the entire volume of the film. Unlike conventional exchange-biased magnetic multilayer systems, the nanocomposite exhibits markedly slow spin dynamics near the magnetic transition region, as evidenced by strong frequency dependence of AC susceptibility. This behavior is attributed to the complex magnetic energy landscape caused by the disordered distribution of AFM regions surrounding the FM phase. At lower temperatures below the blocking point, the FM PtNi phase becomes strongly exchange-coupled with the adjacent AFM CoO, leading to a magnetically frozen state. These observations indicate a re-entrant magnetic glass behavior originated from the nanoscale interfacial frustration in the spontaneously formed multiple magnetic nanophases.

2026-04-30T15:00:00Z Shim, Je-Ho Zhao, Yunxiu Mustaghfiroh, Qoimatul Thi, Nguyen Le Rahmani, Fathiya Kim, Kyungwan Shin, Hee Jun Park, Jaehun You, Xiao Wan, Caihua Jung, Min-Seung Hong, Jung-Il Han, Xiufeng Piao, Hong-Guang Kim, Dong-Hyun https://scholar.dgist.ac.kr/handle/20.500.11750/60020 2026-02-10T09:10:19Z 2026-01-31T15:00:00Z

Title: Terahertz Emission Modulation Caused by Ultrafast Breaking and Recovery of Exchange Bias Author(s): Shim, Je-Ho; Zhao, Yunxiu; Mustaghfiroh, Qoimatul; Thi, Nguyen Le; Rahmani, Fathiya; Kim, Kyungwan; Shin, Hee Jun; Park, Jaehun; You, Xiao; Wan, Caihua; Jung, Min-Seung; Hong, Jung-Il; Han, Xiufeng; Piao, Hong-Guang; Kim, Dong-Hyun Abstract: Magnetic interfacial exchange bias, as a key control method for spintronic devices, remains unclear in terms of its ultrafast dynamic behavior and its role in regulating spintronic terahertz emissions. In this work, femtosecond optical pulses are used to excite ferromagnetic/antiferromagnetic bilayer films with interfacial exchange bias, and a significant modulation phenomenon of terahertz emission is observed by comparing samples with different magnetization pinning states induced by exchange bias. Through the measurement of dynamic hysteresis loops under femtosecond optical pulse excitation, it is confirmed that the optical pulse can rapidly break and then recover the exchange bias within the picosecond time scale. This transient reconstruction process of exchange bias effectively enhances the ultrafast spin precession signal at approximate to 2 THz, while suppressing the ultrafast demagnetization-related signal at approximate to 0.77 THz. By exploiting the difference in flip symmetry of the samples, this is found that the photo-introduced magnetization dynamics process dominated the modulation effect of the exchange bias on the two frequency bands. These results reveal that picosecond-scale transient exchange bias can regulate both the frequency content and coherence of spintronic terahertz emission, offering a pathway toward tunable terahertz spintronic sources.

2026-01-31T15:00:00Z