Search

Doping of rhombohedral bismuth ferrite (BFO) with rare earth elements has been widely investigated as a pathway to extract ferromagnetic response from an otherwise antiferromagnetic material. However, increased level of such doping, in conjunction with the ability of BFO to accommodate large strain, has also resulted in nontrivial changes in the structure, i.e., transition to orthorhombic structure and phase separation to form vertically aligned columns. Herein, epitaxially grown and single crystalline samarium oxide (Sm2O3) and doped BFO films are used to investigate the structural evolution. Thin films are grown from undoped (BFO and Sm2O3) and doped targets, (0.2,0.5)Sm2O3–(0.8,0.5)BFO. In addition, the in‐plane strain, imposed by the lattice mismatch between film and substrates, is used to demonstrate the stability of the structures formed in the doped films. Interestingly, the resultant orthorhombic structures are found to be largely independent of the underlying substrates. In‐depth structural and nanoscopic measurements are conducted to investigate the structures. Ordered columnar structures, reminiscent of phase separation, are successfully obtained albeit driven by spontaneous ordering of differently oriented crystals. [ABSTRACT FROM AUTHOR]

We report the observation of nano-scale precipitates corresponding to a new structure not displayed by the phase diagram of bismuth iron oxide. BiFeO (BFO) thin films grown on terbium scandate and strontium titanate substrates by pulsed laser deposition were investigated using high-resolution transmission and scanning transmission electron microscopy. Precipitate-like structures with a so far unknown metastable phase of bismuth, iron, and oxygen were observed in these films. They consist of well-ordered BiO layers, as they are known from bismuth oxide layered compounds. They have a pseudo-orthorhombic structure with a single perovskite-like unit (FeO) sandwiched between BiO layers, similar to the Aurivillius phase BiWO, with a chemical composition of the precipitates of BiFeO. The structure of the new phase with its lattice constants was elucidated and the band gap of the precipitates was determined by electron energy loss spectroscopy. The results point to promising future applications for this new phase in the field of electronics, if it might be grown phase pure as an epitaxial thin film. [ABSTRACT FROM AUTHOR]