Thermal phase transformation of ZnO-based transparent ferromagnetic composite films and the change in magnetic characteristics

Transparent ferromagnetic semiconducting composite Fe-Zn-O films composed of wurtzite ZnO matrix and Zn-incorporated magnetite particles have been prepared by novel chemical solution processes followed by thermal annealing, performed at different temperatures between 200 and 700°C under vacuum at around 5× 10-4 Pa. The effects of the thermal annealing on the structure and magnetic, electrical, and optical properties of the heterogranular transition metal oxides (Fe-Zn-O) films have been studied by using X-ray diffraction, X-ray absorption fine structure (XAFS), vibrating sample magnetometer, soft X-ray magnetic circular dichroism (SXMCD), and so on. These properties strongly depended on the annealing temperature and could be correlated to the changes in the ZnO matrix and/or the Zn-incorporated magnetite phase. The XAFS and SXMCD measurements using synchrotron radiation elucidated the growth process of the Zn-incorporated magnetite phase in the ZnO matrix.