# Intrinsic Exchange Bias from Interfacial Reconstruction in an Epitaxial NixCoyFe3-x-yO4(111)/{\alpha}-Al2O3(0001) Thin Film Family

## TL;DR

This study demonstrates that intrinsic exchange bias in Ni-Co-Fe spinel oxide films on Al2O3 substrates arises from interfacial reconstruction forming a CoO layer, with tunability via stoichiometry and interface engineering.

## Contribution

It reveals that intrinsic exchange bias is a general phenomenon caused by interfacial reconstruction in (Ni, Co, Fe)-based spinel oxides on Al2O3, highlighting a new interface engineering strategy.

## Key findings

- Intrinsic exchange bias correlates with Co concentration.
- Interfacial reconstruction leads to CoO formation.
- Exchange bias tunability via stoichiometry.

## Abstract

Intrinsic exchange bias is known as the unidirectional exchange anisotropy that emerges in a nominally single-component ferro-(ferri-)magnetic system. In this work, with magnetic and structural characterizations, we demonstrate that intrinsic exchange bias is a general phenomenon in (Ni, Co, Fe)-based spinel oxide films deposited on {\alpha}-Al2O3(0001) substrates, due to the emergence of a rock-salt interfacial layer consisting of antiferromagnetic CoO from interfacial reconstruction. We show that in NixCoyFe3-x-yO4(111)/{\alpha}-Al2O3(0001) films, intrinsic exchange bias and interfacial reconstruction have consistent dependences on Co concentration y, while the Ni and Fe concentration appears to be less important. This work establishes a family of intrinsic exchange bias materials with great tunability by stoichiometry and highlights the strategy of interface engineering in controlling material functionalities.

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Source: https://tomesphere.com/paper/2302.13227