Change of Magnetic Properties and Structure in Fe<SUB>3</SUB>O<SUB>4</SUB> Films on Si Substrates with Annealing Temperature

Abstract

We have investigated the magnetic properties and structure of Fe3O4 films on Si substrates before and after annealing at various temperatures, Ta. The saturation magnetization and the coercivity in the Fe3O4 films are observed at all Ta. They markedly increase with increasing Ta up to 873 K, and their values become maximum at Ta=873 K. Furthermore, they slightly decrease above Ta=873 K. The Fe3O4 phase mainly exists in the films at all Ta. In addition, the α-Fe2O3 phase (hematite) is also formed in the films above Ta=873 K. On the basis of these results, it is found that the growth of Fe3O4 phase by annealing is mainly dominant in the change of magnetic properties in the Fe3O4 film up to Ta=873 K and that the formation of α-Fe2O3 phase influences the change of magnetic properties in the Fe3O4 film above Ta=873 K.