The nanostructural evolution of the strain-induced structural phase transition in BiFeO 3 is examined. Using high-resolution X-ray diffraction and scanning-probe microscopy-based studies we have uniquely identified and examined the numerous phases present at these phase boundaries and have discovered an intermediate monoclinic phase in addition to the previously observed rhombohedral-and tetragonallike phases. Further analysis has determined that the so-called mixed-phase regions of these films are not mixtures of rhombohedral-and tetragonal-like phases, but intimate mixtures of highly-distorted monoclinic phases with no evidence for the presence of the rhombohedral-like parent phase. Finally, we propose a mechanism for the enhanced electromechanical response in these films including how these phases interact at the nanoscale to produce large surface strains.

Developing efficient and durable electrocatalysts for the oxygen evolution reaction (OER) in acidic media is attractive but still challenging. In this study, ultrafine defective RuO2 nanoparticles are successfully prepared on carbon cloth by means of dip‐coating, annealing, and acid etching. As a self‐supported electrocatalyst, it exhibits an ultralow overpotential of 179 mV in 0.5 m H2SO4. More importantly, the high activity can be well maintained for 20 h. The density functional calculations revealed that the defect can not only increase the number of active sites but also improve the intrinsic OER activity.

magnetoelectrics and multiferroics present exciting opportunities for electric-field control of magnetism. However, there are few room-temperature ferromagnetic-ferroelectrics. Among the various types of multiferroics the bismuth ferrite system has received much attention primarily because both the ferroelectric and the antiferromagnetic orders are quite robust at room temperature. Here we demonstrate the emergence of an enhanced spontaneous magnetization in a strain-driven rhombohedral and super-tetragonal mixed phase of BiFeo 3 . using X-ray magnetic circular dichroism-based photoemission electron microscopy coupled with macroscopic magnetic measurements, we find that the spontaneous magnetization of the rhombohedral phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent tetragonal-like phase and the epitaxial constraint. Reversible electric-field control and manipulation of this magnetic moment at room temperature is also shown.