Effects of uniaxial strain on magnetic interactions in Co-doped ZnO nanowires: First-principles calculations

By use of first-principles calculations, we examine the effects of uniaxial strain on the electronic and magnetic properties of Co-doped ZnO nanowires. Our results show that the uniaxial strain can cause significant variation of magnetic interactions in different ways, which are strongly dependant on the configuration formed by Co atoms. For the configuration whose ground state is a ferromagnetic state, the uniaxial tensile strain leads to the enhancement of ferromagnetic interaction, which can be explained by the double-exchange model very well. It is also shown that the strength of the double-exchange interaction is dependent on the occupation of the Co-3 d state. The present results indicate the strain can be used as an effective means in tuning the magnetic interactions in ZnO based one-dimensional diluted magnetic semiconductors.