Large magnetoelectric coupling in multiferroic oxide heterostructures assembled via epitaxial lift-off.

Epitaxial films may be released from growth substrates and transferred to structurally and chemically incompatible substrates, but epitaxial films of transition metal perovskite oxides have not been transferred to electroactive substrates for voltage control of their myriad functional properties. Here we demonstrate good strain transmission at the incoherent interface between a strain-released film of epitaxially grown ferromagnetic La0.7Sr0.3MnO3 and an electroactive substrate of ferroelectric 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 in a different crystallographic orientation. Our strain-mediated magnetoelectric coupling compares well with respect to epitaxial heterostructures, where the epitaxy responsible for strong coupling can degrade film magnetization via strain and dislocations. Moreover, the electrical switching of magnetic anisotropy is repeatable and non-volatile. High-resolution magnetic vector maps reveal that micromagnetic behaviour is governed by electrically controlled strain and cracks in the film. Our demonstration should inspire others to control the physical/chemical properties in strain-released epitaxial oxide films by using electroactive substrates to impart strain via non-epitaxial interfaces.

Hysteretic vortex pinning in superconductor-ferromagnet nanocomposites.

This Letter reports the observation of hysteresis in the vortex pinning in a superconductor-ferromagnetic epitaxial nanocomposite consisting of fcc Gd particles incorporated in a Nb matrix. We show that this hysteretic pinning is associated with magnetic reversal losses in the Gd particles and is fundamentally different in origin to pinning interactions previously observed for ferromagnetic particles or other microstructural features.

Topographic contrast of partially wetting water droplets in environmental scanning electron microscopy.

Partially wetting water droplets with sizes smaller than the capillary length acquire a distinct spherical cap shape controlled by the equilibrium contact angle, which is specific for different substrates and conditions. Images of such droplets in an environmental scanning electron microscope (ESEM) show strong topographic contrast. This contrast across the droplets can be analysed within a simple theoretical model, as the droplet sides are inclined smooth surfaces. Very small droplets have ESEM intensity profiles which deviate from this topographic model. Such deviations indicate that other sources of electron signal may be important for such droplets, and also demonstrate the limits of the analytical model. For droplets sufficiently large that they lie within the range of the topographic contrast model, values of contact angles on different substrates can be deduced. These are found to agree with independent direct measurements, as well as the results given in the literature. The possibilities of using this technique to analyse physical properties of different substrates are discussed.