Magnetic behaviour of sol-gel driven BiFeO3 thin films with different grain size distribution

BiFeO3 (BFO) thin films with uniform thickness of similar to 200 nm were prepared by the sol-gel assisted spin coating method. Different grain size distributions in the as-grown BFO films were then induced by varying the annealing temperature between 525 and 600 degrees C. It is found that the grain size distribution become wider as the annealing temperature increases. All the films showed a well-saturated magnetization (M) versus magnetic field (H) hysteresis loops at 300 K. A strong dependence of M on the grain size distribution is observed. An optimal grain size distribution with average grain size similar to 90 nm is responsible for high M in the BFO films. The non-saturated M-H loops obtained at 10 K suggest the spin glass behaviour of BFO films. The zero field cooled (ZFC) and field cooled (FC) magnetization curves shows split at 300 K and a cusp at similar to 50 K in the ZFC curve, which further confirms the spin glass state of polycrystalline BFO thin films. (C) 2015 Elsevier B.V. All rights reserved.