Interface Modeling Leading to Giant Exchange Bias from the CoO/CoFe2O4 Quantum Dot Heterostructure

Abstract

Research in miniaturization of devices is driven by the presence of new challenges in small-sized particles. Magnetic interactions at the heterostructure interface, specifically the interface-driven properties such as exchange bias (EB) in core–shell magnetic quantum dots (QDs), have become one of the primary fields of interest in nanomagnetism research. The major deterrent in small-sized QDs is the presence of superparamagnetic limit, responsible for low or insignificant anisotropy in these materials. Formation of a sharp interface at the junction of antiferromagnetic (AFM) and ferrimagnetic (FiM) heterostructures can improve anisotropy that can overcome the superparamagnetic limit in these small-sized QDs. Herein, we demonstrate a two-step synthesis of CoO/CoFe2O4 core–shell QDs and their characterization to study the effect of magnetic interaction at the interface. Formation of highly crystalline sharp interfaces, obtained as a result of interface modeling, results in a strong exchange coupling at the AFM core/FiM shell interface, leading to a large EB value (HE = 5.6 kOe). This EB value is comparable with the largest HE value reported for small-sized nanoparticles.