Insights into the room temperature magnetism of ZnO/Co3O4 mixtures

TL;DR

This study investigates the origin of room temperature ferromagnetism in ZnO/Co3O4 mixtures, revealing that surface reduction of Co3O4 nanoparticles leads to magnetic behavior without thermal treatment.

Contribution

It demonstrates that surface reduction of Co3O4 nanoparticles causes room temperature magnetism in ZnO/Co3O4 mixtures, a novel insight into magnetic properties of such composites.

Findings

Surface reduction of Co3O4 nanoparticles induces magnetism.

Magnetic behavior occurs without thermal treatment.

Similar surface magnetism observed in other semiconductor and insulator mixtures.

Abstract

The origin of room temperature (RT) ferromagneticlike behavior in ZnO-based diluted magnetic semiconductors is still an unclear topic. The present work concentrates on the appearance of RT magnetic moments in just mixed ZnO/Co3O4 mixtures without thermal treatment. In this study, it is shown that the magnetism seems to be related to surface reduction of the Co3O4 nanoparticles, in which, an antiferromagnetic Co3O4 nanoparticle (core) is surrounded by a CoO-like shell. This singular superficial magnetism has also been found in other mixtures with semiconductors such as TiO2 and insulators such as Al2O3.