Supplementary Material for

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Facile integration of giant exchange bias in Fe5GeTe2/

oxide heterostructures by atomic layer deposition

Item Type Article

Authors Liang, Jierui;Liang, Shanchuan;Xie, Ti;May, Andrew F.;Ersevim, Thomas;Wang, Qinqin;Ahn, Hyobin;Lee, Changgu;Zhang,

Xixiang;Wang, Jian Ping;McGuire, Michael A.;Ouyang, Min;Gong, Cheng

Citation Liang, J., Liang, S., Xie, T., May, A. F., Ersevim, T., Wang, Q., Ahn, H., Lee, C., Zhang, X., Wang, J.-P., McGuire, M. A., Ouyang, M., & Gong, C. (2023). Facile integration of giant exchange bias in <mml:math xmlns:mml="http://www.w3.org/1998/

Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</

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atomic layer deposition. Physical Review Materials, 7(1). https://

doi.org/10.1103/physrevmaterials.7.014008 Eprint version Publisher's Version/PDF

DOI 10.1103/PhysRevMaterials.7.014008 Publisher American Physical Society (APS)

Journal Physical Review Materials

Download date 2023-11-29 18:41:39

Link to Item http://hdl.handle.net/10754/688154

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Supplementary Material for

Facile integration of giant exchange bias in Fe5GeTe2/oxide heterostructures by atomic layer deposition

Jierui Liang,¹ Shanchuan Liang,¹ Ti Xie,¹ Andrew F. May,² Thomas Ersevim,³ Qinqin Wang,¹ Hyobin Ahn,⁴ Changgu Lee,^4,5 Xixiang Zhang,⁶ Jian-Ping Wang,⁷ Michael A. McGuire,² Min Ouyang,³ Cheng Gong^1*

1Department of Electrical and Computer Engineering and Quantum Technology Center, University of Maryland, College Park, Maryland 20742, USA

2Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

3Department of Physics, University of Maryland, College Park, Maryland 20742, USA

4SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon Gyeonggido 16419, Republic of Korea

5Department of Mechanical Engineering, Sungkyunkwan University, Suwon Gyeonggido 16419, Republic of Korea

6King Abdullah University of Science and Technology (KAUST), Physical Sciences and Engineering Division (PSE), Thuwal, Saudi Arabia.

7Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA

*Corresponding author. Email: [email protected]

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Fig. S1. Remanent RMCD of an exfoliated pristine Fe5GeTe2 flake as a function of

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Fig. S2. Exchange bias measured in two additional Fe5GeTe2/Al2O3 heterostructures after PFC and NFC. (A) Atomic force microscopy images (top row), optical images (inset), and height profiles (bottom row) of two additional Fe5GeTe2/Al2O3 samples. These two samples and the sample shown in Fig. 1E were prepared by ALD using the H2O duration of 200 ms per cycle. The blue lines on atomic force microscopy images indicate the positions where the height profiles were measured. (B) Magnetic hysteresis loops measured by RMCD after PFC (top row) and NFC (bottom row) at the same spot on each sample. Zero magnetic field (x = 0) and zero magnetization (y = 0) for each hysteresis loop are marked by the vertical and horizontal black dashed lines, respectively. The red (blue) dashed lines are the eye guide to visualize the negative (positive) horizontal shifts of the magnetic hysteresis loops. As expected, negative and positive shifts of hysteresis loops emerge after PFC and NFC, respectively. As evident, the exchange bias effect induced by ALD of Al2O3 is reproducible.

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Fig. S3. Exchange bias measured in three additional Fe5GeTe2/Al2O3 heterostructures after zero-field cooling. (A) RMCD measurements after ZFC at different spots on a Fe5GeTe2/Al2O3

sample (oxide prepared by ALD using the H2O duration of 200 ms). The exchange bias field Hex

can be either positive or negative with random amplitudes at different spots on the same sample flake. This is because the multiple magnetic domains can emerge in FM (i.e., Fe5GeTe2) after ZFC, and those magnetic domains with different spin orientations in FM set the interfacial spin directions in the adjacent AFM when the system is cooled below the Néel temperature (TN),¹ leading to the variation of exchange bias across the sample after ZFC. (B) RMCD measurements of two additional Fe5GeTe2/Al2O3 heterostructures after ZFC, showing that exchange bias appears in multiple samples after ZFC.

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Fig. S4. Exchange bias of different Fe5GeTe2/oxides measured at 130 K after NFC versus the corresponding Fe5GeTe2 flake thickness. Hex as a function of Fe5GeTe2 thickness in three types of Fe5GeTe2/oxides: Fe5GeTe2/Al2O3 (left), Fe5GeTe2/ZnO (middle), and Fe5GeTe2/V2O5 (right).

No trend was observed between the magnitude of Hex and the thickness of FM within each type of Fe5GeTe2/oxide. This finding contrasts with the trend in conventional exchange-biased FM/AFM systems where the magnitude of Hex is proportional to the inverse of the FM thickness, but agrees with the recent observations in layered vdW magnets/heterostructures with weak interlayer exchange coupling.^1,2

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Fig. S5. Temperature dependence of exchange bias in a Fe5GeTe2/Al2O3 heterostructure prepared by ALD using O3. (A) Temperature dependence of magnetic hysteresis loops measured at the same spot on a Fe5GeTe2/Al2O3 heterostructure (prepared using the O3 pulse duration of 200 ms per ALD cycle). A positive shift of the hysteresis loop appears at 110 K after NFC, and the hysteresis loop shrinks with the increasing temperature. The black dashed line serves as the eye guide for zero magnetic field (x = 0). Hex (B) and Hc (C) as a function of temperature. Hex reaches 1450 Oe at 170 K. Hc becomes zero at ~180 K. Hex data points beyond 180 K are marked by stars in (B) to indicate the possible uncertainty in extracted values due to the zero Hc. Error bars represent one standard deviation above the mean of the extracted data.

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