Microstructural Underpinnings of Giant Intrinsic Exchange Bias in Epitaxial NiCo2O4 Thin Films

Yang, Detian; Subedi, Arjun; Liu, Chao; Ambaye, Haile; Lauter, Valeria; Dowben, Peter A.; Liu, Yaohua; Xu, Xiaoshan

doi:10.1002/aelm.202400149

Microstructural Underpinnings of Giant Intrinsic Exchange Bias in Epitaxial NiCo₂O₄ Thin Films

Journal Article · Fri Nov 15 00:00:00 EST 2024 · Advanced Electronic Materials

DOI:https://doi.org/10.1002/aelm.202400149· OSTI ID:2538203

^[1]; Subedi, Arjun ^[1]; Liu, Chao ^[2]; ^[3]; ^[3]; Dowben, Peter A. ^[1]; ^[3]; ^[1]

University of Nebraska, Lincoln, NE (United States)
National University of Singapore (Singapore)
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Understanding intrinsic exchange bias in nominally single-component ferromagnetic or ferrimagnetic materials is crucial for simplifying related device architectures. However, the mechanisms behind this phenomenon and its tunability remain elusive, which hinders the efforts to achieve unidirectional magnetization for widespread applications. Inspired by the high tunability of ferrimagnetic inverse spinel NiCo₂O₄, the origin of intrinsic exchange bias in NiCo₂O₄ (111) films deposited on Al₂O₃ (0001) substrates are investigated. The comprehensive characterizations, including electron diffraction, X-ray reflectometry and spectroscopy, and polarized neutron reflectometry, reveal that intrinsic exchange bias in NiCo₂O₄ (111)/Al₂O₃ (0001) arises from a reconstructed antiferromagnetic rock-salt Ni_xCo_1-xO layer at the interface between the film and the substrate due to a significant structural mismatch. Remarkably, by engineering the interfacial structure under optimal growth conditions, it can achieve exchange bias larger than coercivity, leading to unidirectional magnetization. Such giant intrinsic exchange bias can be utilized for realistic device applications. This work establishes a new material platform based on NiCo₂O₄, an emergent spintronics material, to study tunable interfacial magnetic and spintronic properties.

View Accepted Manuscript (DOE)

Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 2538203

Journal Information:: Advanced Electronic Materials, Journal Name: Advanced Electronic Materials Journal Issue: 2 Vol. 11; ISSN 2199-160X

Publisher:: WileyCopyright Statement

Country of Publication:: United States

Language:: English

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36 MATERIALS SCIENCE
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