Stabilization of weak ferromagnetism by strong magnetic response to epitaxial strain in multiferroic BiFeO3.

Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption. However, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications. Here, we explore the stabilization and switchability of the weak ferromagnetic moments under applied epitaxial strain using a combination of first-principles calculations and group-theoretic analyses.

Understanding Strain-Induced Phase Transformations in BiFeO Thin Films.

Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO thin films, which comprises a tetragonal-like (') and an intermediate ' polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniform ' phase. This strain-induced phase transformation is investigated through a synergistic combination of first-principles theory and experiments.

Facet-dependent disorder in pristine high-voltage lithium-manganese-rich cathode material.

Defects and surface reconstructions are thought to be crucial for the long-term stability of high-voltage lithium-manganese-rich cathodes. Unfortunately, many of these defects arise only after electrochemical cycling which occurs under harsh conditions, making it difficult to fully comprehend the role they play in degrading material performance. Recently, it has been observed that defects are present even in the pristine material.

Electric-field-induced patterns in soft viscoelastic films: from long waves of viscous liquids to short waves of elastic solids.

We show that the electric field driven surface instability of viscoelastic films has two distinct regimes: (1) The viscoelastic films behaving like a liquid display long wavelengths governed by applied voltage and surface tension, independent of its elastic storage and viscous loss moduli, and (2) the films behaving like a solid require a threshold voltage for the instability whose wavelength always scales as approximately 4xfilm thickness, independent of its surface tension, applied voltage, loss and storage moduli. Wavelength in a narrow transition zone between these regimes depends on the storage modulus.