Colossal intrinsic exchange bias from interfacial reconstruction in epitaxial CoFe₂ O₄/Al₂ O₃ thin films

Authors

Detian Yang, University of Nebraska–LincolnFollow
Yu Yun, University of Nebraska–Lincoln
Arjun Subedi, University of Nebraska–LincolnFollow
Nicholas E. Rogers, Missouri State University
David M. Cornelison, Missouri State University
Peter Dowben, University of Nebraska - LincolnFollow
Xiaoshan Xu, University of Nebraska-LincolnFollow

ORCID IDs

Detian Yang https://orcid.org/0000-0001-8807-3041

Yu Yun https://orcid.org/0000-0002-4893-7156

David M. Cornelison https://orcid.org/0000-0002-9728-7305

Peter A. Dowben https://orcid.org/0000-0002-2198-4710

Xiaoshan Xu https://orcid.org/0000-0002-4363-392X

Date of this Version

6-1-2021

Citation

PHYSICAL REVIEW B 103, 224405 (2021)

DOI: 10.1103/PhysRevB.103.224405

Comments

©2021 American Physical Society. Used by permission.

Abstract

We have studied the epitaxial CoFe₂O₄ (111) films grown on Al₂O₃ (0001) substrates of different thickness at various temperature and discovered colossal intrinsic exchange bias up to 7 ± 2 kOe. X-ray and electron diffraction clearly indicate an interfacial layer about 2 nm of different crystal structure from the “bulk” part of the CoFe₂O₄ film. The thickness dependence of the exchange bias suggests a hidden antiferromagnetic composition in the interfacial layer that couples to the ferrimagnetic “bulk” part of the CoFe₂O₄ film as the origin of the exchange bias. Considering the structural, magnetic, and electronic structure, CoO has been identified as the most likely candidate of the antiferromagnetic composition in the interfacial layer. This work suggests a path for enhancing intrinsic exchange bias using combination of film and substrate of large structural differences, highlighting the role of interfacial atomic and electronic reconstructions.