Spin wave study and optical properties in Fe-doped ZnO thin films prepared by spray pyrolysis technique

• The magnetic and optical properties of Fe-doped ZnO thin films were studied.
• The spin wave theory allows to separate the M (T) curve in two contributions.
• Ab-initio calculations show the importance of oxygen vacancies in obtaining ferromagnetism.
• Several optical parameters were determined and linked to the Fe content.

We investigate the magnetic and optical properties of Zn1-xFexO (x = 0, 0.03, 0.05, and 0.07) thin films grown by spray pyrolysis technique. The magnetization as a function of temperature [M (T)] shows a prevailing paramagnetic contribution at low temperature. By using spin wave theory, we separate the M (T) curve in two contributions: one showing intrinsic ferromagnetism and one showing a purely paramagnetic behavior. Furthermore, it is shown that the spin wave theory is consistent with ab-initio calculations only when oxygen vacancies are considered, highlighting the key role played by structural defects in the mechanism driving the observed ferromagnetism. Using UV–visible measurements, the transmittance, reflectance, band gap energy, band tail, dielectric coefficient, refractive index, and optical conductivity were extracted and related to the variation of the Fe content.

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