Texture control of multiferroic BiFeO3 polycrystalline films on glass substrates with various metal electrode underlayers Enhanced ferroelectric and ferromagnetic properties in lead-free multilayer composite films based on ferroelectric (Bi0.5Na0.5)0.945Ba0.055TiO3 and multiferroic BiFeO3 J. Appl. Phys. 117, 064105 (2015); 10.1063/1.4908069 0.7BiFeO3-0.3BaTiO3-Y3Fe5O12 composites with simultaneously improved electrical and magnetic properties Effect of Ba substitution on the multiferroic properties of non-epitaxially grown polycrystalline Bi 1Àx Ba x FeO 3 (BBFO) films on refined Pt(111) electrode buffered glass substrates is studied. The structural analysis shows that a pure perovskite phase is present for BBFO films (x ¼ 0.05-0.15), and (110) preferred orientation is developed for films with high x ¼ 0.15. The grain size and surface roughness are reduced with increasing x. All studied BBFO films show desired ferroelectric and ferromagnetic properties. The good ferroelectric properties with the remanent polarization (2P r ) of 36-70 lC/cm 2 and electrical coercive field (E c ) of 318-570 kV/cm are attained. On the other hand, the substitution of Ba 2þ for Bi 3þ in the A site of the BFO crystal structure can effectively enhance the ferromagnetic properties with magnetization (M s ) of 9.4-13.9 emu/cm 3 and coercivity (H c ) of 1216-1380 Oe. The ferromagnetic and ferroelectric properties and leakage behavior as functions of Ba content x are discussed. V C 2015 AIP Publishing LLC.

A large increase in ferromagnetic Curie temperature from 69.5°K to ∼190°K has been observed in EuO films doped with Fe. These films retain most of the large magneto-optic rotation of EuO (at 4.2°K) desired for beam addressable memories. However, the increase in Tc permits the operation of these devices at the more convenient liquid-nitrogen temperature. Films were prepared by simultaneous evaporation of Eu, Eu2O3, and Fe at pressure of 2×10−5 Torr. The amount of Tc increase is strongly dependent upon composition. For example, films with the highest Tc require Fe/Fe+Eu∼0.07 and excess Eu with a typical weight ratio of Eu/Eu2O3∼1.3 as compared to ∼0.9 for pure EuO. The analysis by Seeman-Bohlin x-ray diffractometer shows the same NaCl structure as that of pure EuO with a slightly larger lattice parameter (5.1564 Å). The doping also causes a reduction of grain size (from 200 to 120 Å) and a tendency toward preferred orientation. Results of electron microprobe spectroscopy and Mössbauer measurements show that the iron is predominantly present in the metallic state and the europium in the Eu+ + state. The dependence of physical properties on fabrication parameters will be critically examined.

Structure and ferroelectric properties of multiferroic BiFeO3 (001) films grown on Pt(111) buffer layer with thicknesses of 5–50 nm on glass substrate at 500 °C have been studied. (001) texture of the perovskite BiFeO3 (BFO) could be developed. Grain size and morphology of the BFO(001) films were closely related to those of Pt electrode although no epitaxial growth was evidenced. The optimized BFO layer which exhibited the ferroelectric performance comparable to those with SrRuO3 under layer could be achieved in the samples with Pt thickness in the range of 10 to 20 nm. Different from the polycrystalline BFO/SrRuO3 films, large grain size for 50-nm-thick Pt underlayer causes degeneration of both the ferroelectric properties and the (001)-texture due to the formation of the secondary B2O3 phase. On the other hand, reducing Pt thickness to 5 nm resulted in the induction of the pinholes and thus the increase of the leakage current density. The presented results reveal that a smooth interface between the Pt electrode and BFO layer is essential to achieve good ferroelectric properties.

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