# Interface magnetism and electronic structure: ZnO(0001)/Co3O4(111)

## TL;DR

This study uses density functional theory to explore the magnetic and electronic properties of Co3O4/ZnO interfaces, revealing surface-induced magnetism that could explain ferromagnetism in Co-doped ZnO semiconductors.

## Contribution

It provides a detailed theoretical analysis of Co3O4/ZnO interfaces, highlighting the emergence of surface magnetism in Co ions, which is a novel insight into DMS magnetism.

## Key findings

- Co^{3+} ions gain magnetic moments at surfaces and interfaces.
- Surface magnetism may explain ferromagnetism in Co-doped ZnO.
- Interfaces exhibit ferromagnetic ordering due to surface effects.

## Abstract

We have studied the structural, electronic and magnetic properties of spinel $\rm Co_3O_4$(111) surfaces and their interfaces with ZnO (0001) using density functional theory (DFT) within the Generalized Gradient Approximation with on-site Coulomb repulsion term (GGA+U). Two possible forms of spinel surface, containing $\rm Co^{2+} $ and $\rm Co^{3+} $ ions and terminated with either cobalt or oxygen ions were considered, as well as their interface with zinc oxide. Our calculations demonstrate that $\rm Co^{3+} $ ions attain non-zero magnetic moments at the surface and interface, in contrast to the bulk, where they are not magnetic, leading to the ferromagnetic ordering. Since heavily Co-doped ZnO samples can contain $\rm Co_3O_4 $ secondary phase, such a magnetic ordering at the interface might explain the origin of the magnetism in these diluted magnetic semiconductors (DMS).