Preparation And Properties Investigation Of Gd³⁺ And Al³⁺ Co-Doped BiFeO₃ Thin Film

BiFeO₃ was considered to have good potential applications in the filed of sensors,devices and spintronics and so on,due to its ferroelectric order and G-type anti-ferromagnetic order at room temperature and high Curie temperature(T_c=1103K)and Neel temperature(T_c=643K).However,a large leakage current and weak ferromagnetic property limit its application.In order to improve the ferroelectic and weak ferromagnetic of BiFeO₃ film,the methods of doping and growing epitaxial films were employed in this paper.Firstly,randomly oriented Bi_1-xGd_xFeO₃(x=0.05?0.10?0.15?0.20)and BiFe_1-yAl_yO₃(y=0.03?0.05?0.08)films were prepared on Si substrates by sol-gel method.The result indicate that Gd₃₊and Al single doping with a suitable content could effectively prohibit the formation of impurity phase.Bi_0.9Gd_0.1FeO₃ film exhibits good ferroelectric property(Pr=33.8?C/cm²),but the saturated hysteresis loop couldn't be observed.And Al doping could decrease the leakage current density and slightly improve the ferroelectric and ferromagnetic property of BiFeO₃ film.In order to improve the ferroelectric and ferromagnetic property of BiFeO₃ film,Gd₃₊?Al₃₊co-doping BiFeO₃ film were prepared on Si substrates.The result indicate that Gd₃₊and Al₃₊co-doping could decrease the leakage current density and further improve the ferromagnetic property of BiFeO₃ film.The leakage current density of Bi_0.9Gd_0.1Fe_0.95Al_0.05O₃ film reduced to 5×10-5A/cm²,the remnant polarization and maximum magnetization were increased to 41.0?C/cm²?51.0emu/cm³,respectively.Bi_0.9Gd_0.1Fe_0.95Al_0.05O₃ epitaxial films on Si has saturated hysteresis loop(Ms=32.9emu/cm³).Bi_0.9Gd_0.1Fe_0.95Al_0.05O₃ epitaxial films were prepared on LAO substrates to further improve the ferroelectric and ferromagnetic property.The results show that the ferroelectric and ferromagnetic property of Bi_0.9Gd_0.1Fe_0.95Al_0.05O₃ epitaxial films which were prepared on LAO substrates with LNO and LSMO as bottom electrodes higher than randomly oriented BGFAO film.The leakage current density of Bi_0.9Gd_0.1Fe_0.95Al_0.05O₃ film which was prepared on LNO reduced to 1.63×10-5A/cm²,the remnant polarization was 49.6?C/cm²,the saturation magnetization was 39.7emu/cm³;the leakage current density of Bi_0.9Gd_0.1Fe_0.95Al_0.05O₃ film which was prepared on LSMO reduced to 10-5A/cm²,the magnetization and remnant polarization promoted to 49.6?C/cm²?51.7emu/cm³,respectively.