Thickness dependent magnetic and ferroelectric properties of LaNiO3 buffered BiFeO3 thin films

• BFO thin films have been prepared by radio frequency sputtering method.
• LNO buffer layer is effective in the formation and crystallization of BFO phase.
• Well-developed ferroelectric hysteresis loops were obtained for films with t > 200 nm.
• Leakage current dominated the ferroelectric properties in the thinner ones.
• The magnetic properties are enhanced with decreasing films thickness.

BiFeO3 (BFO) thin films with thickness increasing from 40 to 480 nm were successfully grown on LaNiO3 (LNO) buffered Pt/Ti/SiO2/Si(100) substrate and the effects of thickness evolution on magnetic and ferroelectric properties are investigated. The LNO buffer layer promotes the growth and crystallization of BFO thin films. Highly (100) orientation is induced for all BFO films regardless of the film thickness together with the dense microstructure. All BFO films exhibited weak ferromagnetic response at room temperature and saturation magnetization is found to decrease with increase in film thickness. Well saturated ferroelectric hysteresis loops were obtained for thicker films; however, the leakage current dominated the ferroelectric properties in thinner films. The leakage current density decreased by three orders of magnitude for 335 nm film compared to 40 nm film, giving rise to enhanced ferroelectric properties for thicker films. The mechanisms for the evolution of ferromagnetic and ferroelectric characteristics are discussed.