We report the observation of room temperature ferromagnetism in high quality, single crystalline dilute Fe-doped BaTiO 3. The large equilibrium solubility of Fe ions in the matrix refutes uncertainties about secondary phase magnetism, which has often eclipsed this interesting field of research. While room temperature ferromagnetism is observed at and above 5% Fe concentrations, one finds a highly concave temperature dependence of the susceptibility. Using detailed ab initio calculation, this has been related to intrinsic magnetic inhomogeneities arising from positional disorder. Apart from providing a mechanism for the observed high temperature ferromagnetism, our results point out that intrinsic disorder is a generic and essential component of dilute magnetism.

Variations of the free volume, O2 permeability, and structure of the Nafion membrane upon ion exchange of H+ with Na+ and K+ were studied. The free volume was quantified using the positron annihilation lifetime (PAL) technique, whereas the polymer structure was characterized by dynamic mechanical analysis (DMA), nanoindentation, and wide-angle X-ray diffraction (WAXD). It was found that the ion exchange significantly expands the free volume and at the same time decreases the O2 permeability. This is opposed to the simple free volume model in which the structure with less open volume is more amenable to lower permeability. Comparison of experimental data collected by different techniques revealed that not only the free volume but also the polymer stiffness plays an essential role in O2 permeation.

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The ortho‐positronium (o‐Ps) lifetime was measured as a function of temperature for the perfluorinated PEMs Nafion NR212 and Aquivion E8705. The o‐Ps lifetime in Aquivion E8705 was found to be shorter than Nafion NR212 in the entire temperature range studied. Abrupt changes in the temperature coefficient of the o‐Ps lifetime were noticed and the α‐relaxation, β‐relaxation, and stress relief temperatures were identified. It turned out that Aquivion E8705 has higher α‐relaxation and stress relief temperatures than Nafion NR212. Dissociation of the ionic clusters and large change in the nanostructure after heating to 160 °C were observed for Nafion NR212 but not for Aquivion E8705. It is demonstrated that Aquivion E8705 has a higher thermal stability than Nafion NR212. magnified image