Photo-enhanced magnetization in Fe-doped ZnO nanowires

TL;DR

This study demonstrates that light illumination can enhance the ferromagnetic magnetization of Fe-doped ZnO nanowires near room temperature by inducing electron transitions that promote ferromagnetic coupling, advancing optospintronics.

Contribution

It reveals a novel light-induced mechanism for controlling magnetization in Fe-doped ZnO nanowires, linking oxygen vacancies and electron transfer to magnetic state changes.

Findings

Magnetization increases under illumination near room temperature.

Oxygen vacancies facilitate electron transfer that promotes ferromagnetic coupling.

Light can be used to control magnetic properties in ZnO nanostructures.

Abstract

An emerging branch of electronics, the optospintronics, would be highly boosted if the control of magnetic order by light is implemented in magnetic semiconductors nanostructures being compatible with the actual technology. Here we show that the ferromagnetic magnetization of low Fe-doped ZnO nanowires prepared by carbothermal process is enhanced under illumination up to temperatures slightly below room temperature. This enhancement is related to the existence of an oxygen vacancy V$_{\rm O}$ in the neighbouring of an antiferromagnetic superexchange Fe$^{3+}$-Fe$^{3+}$ pair. Under illumination the V$_{\rm O}$ is ionized to V$_{\rm O}^+$ giving an electron to a close Fe$^{3+}$ ion from the antiferromagnetic pair. This light excited electron transition allows the transition of Fe$^{3+}$ to Fe$^{2+}$ forming stable ferromagnetic double exchange pairs, increasing the total magnetization. The results here presented indicate an efficient way to influence the magnetic properties of ZnO based nanostructures by light illumination at high temperatures.