Colossal intrinsic exchange bias in epitaxial CoFe2O4/Al2O3 thin films

TL;DR

This paper reports a significant intrinsic exchange bias in epitaxial CoFe2O4/Al2O3 thin films, attributed to an interfacial CoO layer, highlighting the potential of interfacial engineering to enhance magnetic properties.

Contribution

It demonstrates a colossal intrinsic exchange bias in epitaxial CoFe2O4 thin films and links it to interfacial CoO, offering new insights into magnetic interface control.

Findings

Intrinsic exchange bias of 3 kOe observed

Interfacial CoO layer identified as key factor

Exchange bias shows power-law thickness dependence

Abstract

In this work, we demonstrate a massive intrinsic exchange bias (3 kOe) in epitaxial CoFe2O4(111) thin films deposited on Al2O3(0001) substrates. This exchange bias is indicative of intrinsic exchange or a ferromagnetic material combined with an antiferromagnet. The analysis of structure, magnetism and electronic states corroborate that there is an interfacial layer CoO between the CoFe2O4(111) thin film and the Al2O3(0001) substrate. The power-law thickness dependence of the intrinsic exchange bias verifies its interfacial origin. This work suggests interfacial engineering can be an effective route for achieving large exchange bias.