Ferromagnetism and ferroelectricity of Bi2O3Fe2O3PbTiO3 amorphous oxide films prepared by gel-coating technique

Previously we reported that rf-sputtered Bi2O3Fe2O3ABO3 films (ABO3: Perovskite either of BaTiO3, PbTiO3, or PbZrO3) have pronounced properties exhibiting magnetic as well as dielectric hysteresis loops simultaneously above room temperature for films with a restricted Fe2O3-concentration of about 70 at% after subject to thermal annealing at about 700°C. In the present study, we have prepared the same oxide films by the sol-gel method, where PbTiO3 was chosen for ABO3. It was found that gel-coated films onto glass substrates and/or low-resistivity Si-wafers also possess the properties similar to those of rf-sputtered films. Microstructure of the films was examined by EXAFS measurement at the Fe-absorption edge. It may be concluded that a disordered oxide state having a random glass network structure is essential for realizing magnetic and dielectric ordered state, presumably caused by strong frustration in a glassy antiferromagnet.