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11. Exchange Bias in Weakly Interlayer-Coupled van der Waals Magnet Fe3GeTe2

Author

Gweon, Hyung Keun, Lee, Sang Yeop, Kwon, Hee Young, Jeong, Juyoung, Chang, Hye Jung, Kim, Kyoung-Whan, Qiu, Zi Qiang, Ryu, Hyejin, Jang, Chaun, and Choi, Jun Woo

Subjects
exchange bias, van der Waals magnets, interlayer exchange interaction, interfacial magnetism, interlayer coupling, Fe3GeTe2, Nanoscience & Nanotechnology
Abstract

van der Waals (vdW) magnetic materials provide an ideal platform to study low-dimensional magnetism. However, observations of magnetic characteristics of these layered materials truly distinguishing them from conventional magnetic thin film systems have been mostly lacking. In an effort to investigate magnetic properties unique to vdW magnetic materials, we examine the exchange bias effect, a magnetic phenomenon emerging at the ferromagnetic-antiferromagnetic interface. Exchange bias is observed in the naturally oxidized vdW ferromagnet Fe3GeTe2, owing to an antiferromagnetic ordering in the surface oxide layer. Interestingly, the magnitude and thickness dependence of the effect is unlike those expected in typical thin-film systems. We propose a possible mechanism for this behavior, based on the weak interlayer magnetic coupling inherent to vdW magnets, demonstrating the distinct properties of these materials. Furthermore, the robust and sizable exchange bias for vdW magnets persisting up to relatively high temperatures presents a significant advance for realizing practical two-dimensional spintronics.

Published
2021

18. Enhanced Fast‐Discharging Performance and Cyclability in Oxygen‐Redox‐Based P3‐Type Na‐Layered Cathode via Vacancies in TM layers.

Author

Lee, Sang‐Yeop, Kweon, Hyunji, Lee, Sangyeop, Cho, Min‐kyung, Ahn, Hobin, Ahn, Jinho, Ku, Bonyoung, Choi, Myungeun, Jung, Hun‐Gi, Shin, Dong Ok, and Kim, Jongsoon

Subjects
*PHASE transitions, *ENERGY density, *CATHODES, *OXIDATION-reduction reaction, *VOLTAGE
Abstract

Oxygen redox in layered oxide cathodes for Na‐ion batteries is considered a promising approach for improving the energy density. However, oxygen‐redox‐based cathodes suffer from sluggish kinetics and undesirable structural change during charge/discharge, leading to poor electrochemical performances. Herein, introducing vacancies (□) in the transition metal layers enables the enhanced oxygen redox‐based electrochemical performances in the P3‐type Mn‐based layered oxide cathode is demonstrated. The vacancies can play a role of the local distortion buffers, resulting in the enhanced oxygen redox kinetics and the suppressed structural deformation such as P3‐O3(II) phase transition. The oxygen‐redox‐based P3‐type Na0.56[Ni0.1Mn0.81□0.09]O2 exhibits the large discharge capacity of ≈140.95 mAh g−1 at 26 mA g−1 with a high average discharge voltage of ≈3.54 V (vs Na+/Na). Even at 650 mA g−1, its discharge capacity and average operation voltages delivered ≈122.06 mAh g−1 and ≈3.22 V, respectively. Especially, the small gap of average discharge voltage indicates both improves power‐capability and enhanced kinetics of oxygen redox in P3‐type Na0.56[Ni0.1Mn0.81□0.09]O2. Moreover, the vacancy buffer in the transition metal layers results in the stable cycle‐performance of P3‐type Na0.56[Ni0.1Mn0.81□0.09]O2 with the capacity retention of ≈80.80% for 100 cycles, due to the suppressed P3‐O3(II) phase transition. [ABSTRACT FROM AUTHOR]

Published
2024
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47. Defect Engineering of Metal Halide Perovskite Nanocrystals via Spontaneous Diffusion of Ag Nanocrystals

Author

Jeon, Sanghyun, primary, Ahn, Junhyuk, additional, Jung, Myung‐Chul, additional, Woo, Ho Kun, additional, Bang, Junsung, additional, Jung, Byung Ku, additional, Oh, Seongkeun, additional, Lee, Sang Yeop, additional, Lee, Kyu Joon, additional, Paik, Taejong, additional, Ha, Don‐Hyung, additional, Ahn, Jae‐Pyoung, additional, Jeong, Sohee, additional, Kim, Dong Hoe, additional, Noh, Jun Hong, additional, Jang, Ho Seong, additional, Han, Myung Joon, additional, and Oh, Soong Ju, additional

Published
2023
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