Reversible Ferromagnetic Switching in Zno:(Co,Mn) Powders

TL;DR

This study investigates the reversible ferromagnetic behavior in ZnO doped with Mn and Co nanoparticles, highlighting the role of surface defects and annealing conditions in modulating magnetic properties.

Contribution

It demonstrates reversible ferromagnetic switching in ZnO:(Co,Mn) powders through low-temperature annealing, emphasizing surface defect influence on magnetic behavior.

Findings

Ferromagnetism in ZnO:Mn can be switched on/off by annealing in O2/N2.

Different defect types are responsible for ferromagnetism in ZnO:Co and ZnO:Mn.

Surface effects are crucial for ferromagnetism in doped ZnO nanoparticles.

Abstract

We report here on the magnetic properties of ZnO:Mn and ZnO:Co doped nanoparticles. We have found that the ferromagnetism of ZnO:Mn can be switched on and off by consecutive low-temperature annealings in O2 and N2 respectively, while the opposite phenomenology was observed for ZnO:Co. These results suggest that different defects (presumably n-type for ZnO:Co and p-type for ZnO:Mn) are required to induce a ferromagnetic coupling in each case. We will argue that ferromagnetism is likely to be restricted to a very thin, nanometric layer, at the grain surface. These findings reveal and give insight into the dramatic relevance of surface effects for the occurrence of ferromagnetism in ZnO doped oxides.