Abstract
van der Waals (vdW) magnetic materials, such as Cr2Ge2Te6 (CGT), show promise for memory and logic applications. This is due to their broadly tunable magnetic properties and the presence of topological magnetic features such as skyrmionic bubbles. A systematic study of thickness and oxidation effects on magnetic domain structures is important for designing devices and vdW heterostructures for practical applications. Here, we investigate thickness effects on magnetic properties, magnetic domains, and bubbles in oxidation-controlled CGT crystals. We find that CGT exposed to ambient conditions for 5 days forms an oxide layer approximately 5 nm thick. This oxidation leads to a significant increase in the oxidation state of the Cr ions, indicating a change in local magnetic properties. This is supported by real-space magnetic texture imaging through Lorentz transmission electron microscopy. By comparing the thickness-dependent saturation field of oxidized and pristine crystals, we find that oxidation leads to a nonmagnetic surface layer that is thicker than the oxide layer alone. We also find that the stripe domain width and skyrmionic bubble size are strongly affected by the crystal thickness in pristine crystals. These findings underscore the impact of thickness and surface oxidation on the properties of CGT, such as saturation field and domain/skyrmionic bubble size, and suggest a pathway for manipulating magnetic properties through a controlled oxidation process.
Original language | English |
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Pages (from-to) | 13458-13467 |
Number of pages | 10 |
Journal | ACS Nano |
Volume | 18 |
Issue number | 21 |
DOIs | |
State | Published - May 28 2024 |
Externally published | Yes |
Funding
This work is primarily supported through the Department of Energy BES QIS program on \u201Cvan der Waals Reprogrammable Quantum Simulator\u201D under Award Number DE-SC0022277 for the work on long-range correlations, as well as partially supported by the Quantum Science Center (QSC), a National Quantum Information Research Center of the U.S. Department of Energy (DOE) on probing quantum matter. M.G. acknowledges support from the Air Force Office of Scientific Research under Award Number FA9550-20-1-0246. The work at the Brookhaven National Laboratory was supported by the U.S. Department of Energy (DOE), Basic Energy Sciences, Materials Science and Engineering Division under Contract No. DESC0012704. K.S.B. acknowledges the primary support of the DOE, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0018675. The authors acknowledge the use of the MIT.nano Characterization Facilities. The authors thank Caroline A. Ross for fruitful discussions. Figure 2a was created using Vesta. P.N. gratefully acknowledges support from the John Simon Guggenheim Memorial Foundation (Guggenheim Fellowship) as well as support from an NSF CAREER Award under Grant No. NSF-ECCS-1944085.
Keywords
- Lorentz transmission electron microscopy
- magnetic two-dimensional materials
- magnetism
- oxidation
- transmission electron microscopy
- two-dimensional materials