Structural and Magnetic Properties of BiFeO3 Thin Films by Sol-Gel

Bismuth iron oxide (BiFeO3) is amongst the class of multiferroic materials that has attracted world attraction because of its antiferromagnetic Neel temperature and high ferroelectric Curie temperature of 643K and 1103K respectively. However, synthesis of pure phase BiFeO3 is extremely difficult due to volatile nature of Bi2O3. This results in the presence of bismuth deficient and bismuth rich phases in pure bismuth iron oxide. In the past attention was focused on obtaining pure BiFeO3 phase with variation in annealing/calcination temperature in the range 400-700˚C, and very little consideration is given to the changes in Bi/Fe ratio during synthesis. We here report synthesis of pure phase bismuth iron oxide thin films using cost effective sol-gel method. The ratio of Bi/Fe is varied as 0.90, 1.0 and 1.10. The films are annealed at 300˚C in vacuum under the application of 500 Oe magnetic field. XRD results show that with Bi/Fe ratio of 1.10 pure phase BiFeO3 can be obtained at low temperature of 300˚C. Bi/Fe ratios of 0.9 and 1.0 result in the presence of bismuth impurity phase. The films show ferromagnetic behavior as opposed to antiferromagnetic nature of bulk BiFeO3 due to suppression of spiral spin structure.