Nanoscale Control of Phase Variants in Strain-Engineered BiFeO₃

Abstract

Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral-tetragonal (R-T) BiFeO(3) (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T → R transition is activated at lower voltages compared to T → -T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale.

Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates

“…1, [12][13][14]16,17 The lattice constants of pseudo-cubic SCRO are 3.92 Å , 3.89 Å , 3.87 Å , and 3.84 Å , for x ¼ 1, 0.67, 0.33, and 0, respectively (as shown below). The lattice constant of bulk BFO is 3.96 Å , which is clearly larger than that of SCRO.…”

“…13 Additionally, transitions between the tetragonal phase and the rhombohedral phase can be controlled by external electrical field 14 and a new temperature-induced phase transitions around 100 C was recently observed in these highly strained BFO films. 15 It seems clear, then that strain considerably affects the magnetic, electrical and piezoelectric behaviors of BFO films.…”

Persistent Photoconductivity in Strained Epitaxial BiFeO3 Thin Films

“…5 The possibility to electrically switch between these two phases, thereby producing efficient electromechanical responses, makes the strained system of BFO a rather attractive lead-free alternative for several applications. 7 Additionally, BFO is a wide band gap (≈ 2.7 eV) oxide semiconductor which allows electronic applications, like resistive switching. 8 Recently, Mössbauer studies revealed a simplified magnetic structure in the strained BFO films and hence they can be of great interest for future spintronic and magnonic devices.…”

Temperature controlled c axis elongated low symmetry phase BiFeO3 thin film on STO substrate

“…It is well known that the formation of T-like phase is a strain induced process, [17][18][19][20] but it is still not very clear whether the strain comes from the substrate lattice, the island growth or both of them. In order to clarify these effects of the two mechanisms, we have grown BFO samples on LAO (001) substrates at different temperatures as on STO substrates.…”