Structure Transition and Improved Multiferroic Properties of Bi1−x Tb x FeO3 (x = 0.00–0.15) Thin Films

We investigated phase constitutions, ferroelectric (FE), and magnetic characteristics of BiFeO3 (BFO) films with Tb substitution. Bi1-xTbxFeO3 (BTFO) ( ${x}$ = 0.00–0.15) thin films were prepared on the Pt-buffered glass substrates by pulsed laser deposition (PLD). BTFO films with ${x}$ = 0.00–0.15 were confirmed to mainly consist of the perovskite phase. The structure in the studied films is transformed from rhombohedral for ${x}$ = 0.00 to pseudo-cubic for ${x}$ = 0.05–0.10, and orthorhombic for ${x}$ = 0.15. The studied BTFO polycrystalline films exhibit the desired FE and ferromagnetic properties at the same time. The remanent polarization ( $2P_{r}$ ) of $157 ~\mu \text{C}$ /cm2 and electrical coercive field ( $E_{c}$ ) of 485 kV/cm are obtained for BTFO films at ${x}$ = 0.05. Besides, the saturation magnetization ( $M_{s}$ ) of 15.0 emu/cm3 is found for $x$ = 0.05 film. The enhanced $M_{s}$ with Bi0.95Tb0.05FeO3 is due to the magnetic moment of the doped Tb $^{3+}$ ion in addition to the suppressed spiral spin configuration. The result of this work indicates that the radius and magnetic moment of the Tb $^{3+}$ ions play a critical role in the structural evolution, refined microstructure, and therefore, enhanced multiferroic (MF) properties for Tb-substituted BFO polycrystalline films.