Imaging and control of surface magnetization domains in a magnetoelectric antiferromagnet.

We report the direct observation of surface magnetization domains of the magnetoelectric Cr(2)O(3) using photoemission electron microscopy with magnetic circular dichroism contrast and magnetic force microscopy. The domain pattern is strongly affected by the applied electric field conditions. Zero-field cooling results in an equal representation of the two domain types, while electric-field cooling selects one dominant domain type. These observations confirm the existence of surface magnetization, required by symmetry in magnetoelectric antiferromagnets.

In situ monitoring of the growth, intermediate phase transformations and templating of single crystal VO2 nanowires and nanoplatelets.

Direct in situ optical and photoelectron emission microscopy observations of the nucleation and growth of VO(2) meso- and nanostructures using thermal transport of V(2)O(5) precursor in a vacuum or in an inert-gas environment were conducted. During nanostructure reductive growth, the formation, coexistence, and transformation of the intermediate oxide phases and morphologies were observed and characterized structurally and compositionally. The composition, structure, and morphology of the resultant nanostructures appeared to be a product of the interplay between kinetic and thermodynamic factors during multiple phase transformations. By rationally "navigating" the growth parameters using knowledge of the vanadium-oxygen temperature-composition phase diagram, wetting behavior, and epitaxial relationships of the intermediate phases with the substrate, control over growth direction, faceting, shape, and elastic strain of the nanostructures can be achieved. Such versatile control over the properties of single-crystal VO(2) nano- and mesostructures will facilitate their application in MEMS, sensors, and optoelectronics.

Phase separation of palmitic acid and perfluorooctadecanoic acid in mixed Langmuir-Blodgett monolayer films.

Deposition of mixtures of palmitic acid (C15H31COOH) and perfluorooctadecanoic acid (C17F35COOH) onto solid substrates gives rise to irregularly shaped, phase-separated domains under a variety of deposition conditions. The morphology and chemical composition of these phase-separated domains have been investigated using a combination of surface pressure-area isotherms, atomic force microscopy, X-ray photoemission electron microscopy, and confocal fluorescence microscopy imaging. While domain morphology and composition in 2D phase-separated mixed monolayer systems can typically be rationalized in terms of an interplay between line tension and dipole-dipole repulsion effects, it was found that for this system additional kinetic factors, including domain growth rates and the rate of dissolution of the fatty acid component into the aqueous subphase, also play a major role in controlling film properties. The potential importance of these effects for the controlled patterning of solid substrates is discussed.