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A key element to tailor the properties of magnetic multilayers is the coupling between the individual magnetic layers. In the case of skyrmion hosting multilayers, coupling of skyrmions across the magnetic layers is highly desirable. Here, the magnetic interlayer coupling was studied in epitaxial all-oxide heterostructures of ferromagnetic perovskite SrRuO 3 layers separated by spacers of the strong spin–orbit coupling oxide SrIrO 3. This combination of oxide layers is being discussed as a potential candidate system to host Néel skyrmions. First order reversal curve (FORC) measurements were performed in order to distinguish between magnetic switching processes of the individual layers and to disentangle the signal of soft magnetic impurities from the sample signal. Additionally, FORC investigations enabled us to determine whether the coupling between the magnetic layers is ferromagnetic or antiferromagnetic. The observed interlayer coupling strength was very weak for the heterostructure with a two monolayer (ML) thick SrIrO 3 spacer, and no coupling was observed for spacers of 6 and 12 ML thickness. The decoupling of the magnetic SrRuO 3 layers due to the SrIrO 3 spacer is a disadvantage for the study of skyrmions in such multilayers and indicates that other oxides have to be identified for realizing strong magnetic coupling. [ABSTRACT FROM AUTHOR]

We employed a multitechnique approach using piezo-force response microscopy and photoemission microscopy to investigate a self-organizing polarization domain pattern in PbTiO3/La0.7Sr0.3MnO3 (PTO/LSMO) nanostructures. The polarization is correlated with the nanostructure morphology as well as with the thickness and Mn valence of the LSMO template layer. On the LSMO dots, the PTO is upwards polarized, whereas outside the nanodots, the polarization appears both strain and interface roughness dependent. The results suggest that the electronic structure and strain of the PTO/LSMO interface contribute to determining the internal bias of the ferroelectric layer. [ABSTRACT FROM AUTHOR]

Epitaxial films and ordered arrays of submicron structures of nickel and cobalt ferrites were deposited on Nb doped SrTiO3 by pulsed laser deposition. X-Ray diffraction and atomic force microscopy showed that the films have a good crystalline quality and smooth surfaces. A larger number of phonon bands was observed in the polarization dependent Raman spectra of the ferrite films than expected for the cubic spinel structures. This is explained by short range ordering of the Ni2+ (or Co2+) and Fe3+ cations at the octahedral sites inducing a lowering of the symmetry. The same behavior was also observed in the Raman spectra measured for the submicron structures, suggesting the same cation distribution as in the films. The diagonal components of the dielectric function for nickel and cobalt ferrites are determined from ellipsometry in the 0.73-5 eV photon energy range. The absorption edge was analyzed using a bandgap model and the energies for the indirect and direct optical transitions were calculated. It was found that both nickel and cobalt ferrites are indirect bandgap materials with bandgaps of 1.65 eV and 1.42 eV, respectively, while the first direct transitions lie at 2.69 eV and 1.95 eV, respectively. Magneto-optical Kerr effect spectroscopy in combination with spectroscopic ellipsometry allowed the off-diagonal elements of the dielectric tensor to be determined in the energy range from 1.7 eV to 5 eV. [ABSTRACT FROM AUTHOR]

We present the complex dielectric function of BiCrO3 thin films in the energy range of 0.73-9.8 eV determined using spectroscopic ellipsometry. By analyzing the absorption onset region, it is shown that the optical bandgap of BiCrO3 is indirect, with a value of 2.27 eV. The imaginary part of the BiCrO3 dielectric function, &eh;2, calculated using density functional theory in the generalized gradient approximation with an Hubbard potential of 3 eV agrees well with the experimentally determined one. Raman spectra of both polycrystalline and epitaxial thin films of BiCrO3 are reported. The temperature dependent Raman measurements indicate a structural phase transition at ∼400 K which was confirmed also by x-ray diffraction investigations. [ABSTRACT FROM AUTHOR]

We have investigated the individual switching of nanoscale capacitors by piezoresponse force microscopy. Nanoscale epitaxial ferroelectric capacitors with terabyte per inch square equivalent density were fabricated by the deposition of top electrodes onto a pulsed laser deposited lead zirconate titanate thin film by electron beam evaporation through ultrathin anodic aluminum oxide membrane stencil masks. Using bias pulses, the nanoscale capacitors were uniformly switched and proved to be individually addressable. These film-based nanoscale capacitors might be a feasible alternative for high-density mass storage memory applications with near terabyte per inch square density due to the absence of any cross-talk effects. [ABSTRACT FROM AUTHOR]

Heterostructures consisting of PbZr0.2Ti0.8O3 and PbZr0.4Ti0.6O3 epitaxial films on a SrTiO3 (100) substrate with a SrRuO3 bottom electrode were prepared by pulsed laser deposition. By using the additional interface provided by the ferroelectric bilayer structure and changing the sequence of the layers, the content of dislocations and elastic domain types was varied in a controlled manner. The resulting microstructure was investigated by transmission electron microscopy. Macroscopic ferroelectric measurements have shown a large impact of the formation of dislocations and 90° domain walls on the ferroelectric polarization and dielectric constant. A thermodynamic analysis using the Landau–Ginzburg–Devonshire approach that takes into account the ratio of the thicknesses of the two ferroelectric layers and electrostatic coupling is used to shed light on the experimental data. [ABSTRACT FROM AUTHOR]

Electrical properties, i.e., dielectric hysteresis and leakage current, of epitaxial Pb(Zr0.2Ti0.8)O3 films with bottom SrRuO3 electrode and different metals as top contact were investigated. The leakage current is largely insensitive to the work function of the top metal but increases with decreasing electronegativity as well as with decreasing number of electrons on the d-shell of the top metal. The best rectifying properties are obtained for metals with complete d-shell (Cu, Au, Ag, Pd), while the metals with few electrons on the d-shell (Ta, Cr) form Ohmic-like contacts. [ABSTRACT FROM AUTHOR]

Heterostructures consisting of Pb[Zr.sub.0.2][Ti.sub.0.8][O.sub.3] and Pb[Zr.sub.0.4][Ti.sub.0.6][O.sub.3] epitaxial films on a SrTi[O.sub.3] (100) substrate with a SrRu[O.sub.3] bottom electrode are prepared by pulsed laser deposition. Macroscopic ferroelectric measurements have a major impact on the formation of dislocations and 90 [degree] domain walls on the ferroelectric polarization and dielectric constant.

The electrical properties like dielectric hysteresis and leakage current of epitaxial Pb([Zr.sub.0.2][Ti.sub.0.8])[O.sub.3] films with bottom SrRu[O.sub.3] electrode and different metals as top contact are studied. The current is mostly insensitive to the work function of the top metal but has increased with the decreasing electronegativity as well as with decreasing number of electrons on the d-shell of the top metal.

We employed a multitechnique approach using piezo-force response microscopy and photoemission microscopy to investigate a self-organizing polarization domain pattern in PbTiO3/La0.7Sr0.3MnO3 (PTO/LSMO) nanostructures. The polarization is correlated with the nanostructure morphology as well as with the thickness and Mn valence of the LSMO template layer. On the LSMO dots, the PTO is upwards polarized, whereas outside the nanodots, the polarization appears both strain and interface roughness dependent. The results suggest that the electronic structure and strain of the PTO/LSMO interface contribute to determining the internal bias of the ferroelectric layer. [ABSTRACT FROM AUTHOR]