Defect-induced room temperature ferromagnetism in Fe and Na co-doped ZnO nanoparticles

The effect of defects in the diluted magnetic semiconductor (DMS) of Fe and Na co-doped ZnO nanoparticles was investigated. Structural characterizations revealed that Fe and Na ions enter into ZnO lattice without any secondary phase. The ferromagnetic behaviors at room temperature were found in all samples, which are attributed to the exchange via electron trapped oxygen vacancies (F-center) coupled with magnetic Fe ions. With the increase of the Na concentration, the oxygen vacancy mediated ferromagnetic state is enhanced. The observed correlation between the Na concentration, the carrier concentration and the magnetization revealed the role of the defect in tuning the ferromagnetism in the ZnO-based DMS system.

► A new defect was introduced by Na co-doping into ZnFeO by sol–gel method. ► The study of structure indicates the ZnFeNaO system remains wurtzite ZnO structure. ► Carrier density and oxygen vacancy concentration changed after Na doping. ► Enhanced ferromagnetism in ZnFeNaO was observed compared with ZnFeO. ► The ferromagnetism is attributed to the defect induced exchange interaction.