Electric and magnetic properties of bilayered lead-free piezoelectric and multiferroic Bi _0.9Dy _0.1 FeO ₃K _0.5Na _0.5 NbO ₃ thin films

Composite lead-free piezoelectric and multiferroic thin films consisting of Bi _0.9 Dy _0.1 FeO ₃ (BDF) and K _0.5 Na _0.5NbO ₃ (KNN) nanolayers were prepared on the Pt TiO ₂SiO ₂Si substrates by pulsed laser deposition. The bilayered BDF / KNN films exhibited a preferential (100)-orientation and much enhanced ferroelectric properties (2P _r = 26.5 μC/cm ², 2E _c = 369.2 kV/cm) as compared to those of single layer BDF or KNN thin film. In addition, the bilayered BDF / KNN films also showed ferromagnetic behavior at low temperature (2M _r = 1.57 emu/cm ³, 2H _c = 3 kOe). The enhanced ferroelectric properties of the bilayered BDF / KNN thin films were attributed to the significantly reduced leakage current arising from the enhanced crystallinity and the interface reaction of the BDF and KNN nanolayers. An effective piezoelectric coefficient d ₃₃ of 12 pm/V was measured on the bilayered films.