Structure transition and enhanced multiferroic properties of Dy-doped BiFeO3 thin films

We investigated phase constitutions, ferroelectric, magnetic, and nanomechanical characteristics of BiFeO3 films with Dy substitution. Bi1−xDyxFeO3 (x = 0.00–0.15) thin film were prepared on the Pt buffered glass substrates by pulsed laser deposition. BDFO films with x = 0.00–0.15 were confirmed to mainly consist of the perovskite phase. The structure is transformed from rhombohedral for x = 0.00 to pseudo-cubic for x = 0.05, and an additional phase, orthorhombic, is coexisted for x = 0.10 and 0.15. The studied BDFO polycrystalline films exhibit the desired ferroelectric and ferromagnetic properties at the same time. The remanent polarization (2Pr) of 165.7 μC/cm2 and electrical coercive field (Ec) of 337.5 kV/cm are obtained for BDFO films at x = 0.05. Leakage mechanisms in BDFO films with various contents x are also discussed. Besides, the saturation magnetization (Ms) of 2.1–26.8 emu/cm3 and coercivity (Hc) of 133–522 Oe are found. The increased Ms with Dy content x is related to the magnetic moment of the doped Dy3+ ion in addition to the suppressed spiral spin configuration. Furthermore, the hardness of 5.3–8.0 GPa for the BDFO films is found. The relationship between the hardness and grain size well agrees with the impeded propagation of dislocation by grain boundary mainly dominates the hardness. The result of this work indicates that the radius and magnetic moment of the Dy3+ ions plays a critical role in the structural evolution, refined microstructure, and therefore enhanced multiferroic and nanomechanical properties for Dy substituted BiFeO3 polycrystalline films.