Grain size distribution dependent magnetic and ferroelectric properties in sol–gel driven BiFeO₃ thin films

The effect of thickness induced grain size distribution on the magnetic and ferroelectric behaviour of sol–gel driven BiFeO₃ (BFO) thin films was investigated in this study. FESEM micrographs showed well-crystallized equiaxed grains with minimal porosity. The magnetization (M) versus magnetic field (H) indicated the well saturated hysteresis loops at 300 K. The saturation magnetization (M_s) is found to decrease from 18.9 to 0.93 emu/cm³ on increasing the film thickness from 156 to 388 nm. The high Ms value obtained in the BFO films due to the uncompensated spins originated at grain boundary tends to decrease with the film thickness. At low temperature (10 K), non-saturated M–H loops are observed due to spin freezing effect. The dielectric and ferroelectric properties improve with better growth and densification of grains in the BFO thin films with increasing thickness.