investigation of ferromagnetism increasing with temperature in n-type ZnO

Shih-Jye Sun^1*, Guan-Long Chen¹

¹Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan

* Presenter:Shih-Jye Sun, email:sjs@nuk.edu.tw

We found in field-cooling experiments that the ferromagnetic moment of n-type ZnO increases with temperature. We proposed a theoretical model to explain this result and found that the electron-phonon interaction plays a critical role in inducing ferromagnetism in n-type ZnO. The model suggests that ferromagnetism comes from the polaronic electrons in the impurity states, and the strong Coulomb interaction causes the electron's spin to split. The hybrid interaction between the conduction band and the impurity states promotes the increasing electron density in the impurity states and the ferromagnetism. While, a too strong hybridization interaction will delocalize the electrons in the impurity states, which will cause a decrease in ferromagnetism.

Keywords: ferromagnetic ZnO, electron-phonon interaction, impurity states