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The crucial role of interface engineering in controlling functionality has been well documented in the (001)-orientated perovskite oxide heterostructures; however, limited attention has been given to other epitaxial orientations. In this study, the (La,Sr)MnO3 heterostructure is selected to present the epitaxial-orientation-dependent interface engineering strategies based on magnetoelectric coupling and oxygen octahedral coupling. When capped by a ferroelectric PbTiO3 layer for interlayer magnetoelectric coupling, the (001) (La,Sr)MnO3 layer exhibits the most significant magnetic modulations compared to (110) and (111) counterparts. This can be attributed to the PbTiO3's out-of-plane polarization that depends on the epitaxial orientations. Also, if considering the interfacial oxygen octahedral structure in terms of epitaxial orientations, the buffer (or cap) layer hosts the most part of interfacial oxygen octahedra and, thus, plays a dominant role in controlling oxygen octahedral coupling of (001)-orientated [or (110)-orientated] perovskite heterostructures. This is consistent with our observations that for the (001) [or (110)] (La,Sr)MnO3 heterostructures, the DyScO3 buffer layer offers the more (or less) effective magnetic modulations compared to the cap one. These findings underscore the orientation-dependent nature of interface engineering in manganite heterostructures as well as in other perovskite heterostructures for tailoring functionalities. [ABSTRACT FROM AUTHOR]

The effects of epitaxial strain on the properties of 0.95(K0.49Na0.49Li0.02)(Ta0.2Nb0.8)O3-0.05CaZrO3 (KNNLT-CZ) thin films are investigated. La0.07Sr0.93SnO3 and SrRuO3 are used as bottom electrodes to provide in-plane tensile and compressive stress, respectively. Our results show that the La0.07Sr0.93SnO3-buffered KNNLT-CZ films are mostly strain-relaxed with an orthorhombic (O) and tetragonal (T) mixed phase and a tetragonality of 1.002, which have a twice remnant polarization (2Pr) of 14.29 μC/cm2, an effective piezoelectric strain coefficient (d33*) of ∼60 pm/V, and an O to T phase transition temperature (TO-T) of 140 °C, while the SrRuO3-buffered KNNLT-CZ films are only partially strain-relaxed with a pure O phase and a larger tetragonality of 1.011, resulting in an increased 2Pr value of 33.63 μC/cm2, an improved d33* value of ∼80 pm/V, and an enhanced TO-T value of 200 °C. Both films show a high Curie temperature above 380 °C and stable hysteresis loops from room temperature to 225 °C. These results highlight the feasibility to improve the performance of KNN-based materials via epitaxial strain. [ABSTRACT FROM AUTHOR]

Electron-electron (e-e) correlation and spin-orbit coupling (SOC) are two essential control parameters that determine the physical properties of transition-metal-oxide-based thin films and heterostructures. Here, by harnessing these two parameters, we report the systematic control of both ferromagnetism and in-plane magnetic anisotropy in La0.67Ca0.33MnO3/CaIr1-xRuxO3 (LCMO/CIRO) superlattices grown on NdGaO3 substrates. In these all-oxide epitaxial systems, we demonstrate that the e-e correlation and the SOC depend strongly on the chemical composition of CIRO layers. By simply increasing the Ru doping level x, we can significantly suppress the degradation of ferromagnetism in ultrathin LCMO layers and enhance the TC by ∼90 K. Moreover, we observe a clear reorientation of the magnetic easy axis from orthorhombic [010] to [100] as x decreased to 0, which may originate from the enhanced SOC. Our work provides an insight for utilizing the 4d/5d transition-metal-oxides to tune the functionality of magnetic heterostructures. [ABSTRACT FROM AUTHOR]

By using highly conductive p-type La0.7Sr0.3MnO3 (LSMO) and n-type La0.07Sr0.93SnO3 (LSSO) as electrodes, all-oxide Pb(Zr0.52Ti0.48)O3 (PZT) capacitors, LSMO/PZT/LSMO, LSSO/PZT/LSSO, LSSO/PZT/LSMO, and LSMO/PZT/LSSO, have been grown epitaxially on (001)SrTiO3 substrates, and their structure, switching, fatigue, and optical properties were investigated. Strikingly, contrary to the LSMO/PZT/LSMO capacitors, those having the n-type electrode show poor fatigue resistance especially at lower driving frequencies, which was further confirmed by using another n-type oxide electrode, SrTi0.9Sb0.1O3. The results suggest that with a depletion layer at the PZT/LSSO interface, charge accumulation and injection during switching may be responsible for the fatigue. [ABSTRACT FROM AUTHOR]

Conductive and transparent La0.07Sr0.93SnO3 (LSSO) films were employed as electrodes for the fabrication of epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) ferroelectric capacitors. Due to a negligible lattice mismatch between LSSO and PZT, the LSSO/PZT/LSSO heterostructures grown on SrTiO3(001) substrates show excellent single-crystalline quality as revealed by high-resolution x-ray diffraction and are transparent with transmittance comparable to that of pure SrTiO3(001) substrates at the wavelength of 400–2500 nm. These capacitors show square polarization–electric field hysteresis loops but smaller polarization, larger coercive field, and especially poor fatigue resistance, in sharp contrast with those observed for the conventional epitaxial all-oxide PZT capacitors. [ABSTRACT FROM AUTHOR]

Epitaxial La0.7Ca0.3MnO3 (LCMO) films of 15–150 nm thick have been grown on SrTiO3(001) [STO(001)] and (LaAlO3)0.3(Sr2AlTaO6)0.7(001) [LSAT(001)] substrates with lattice mismatches of 1.11% and 0.15%, respectively. Asymmetric x-ray reciprocal space mapping was used to determine the strain state evolution in the films. For LCMO/STO(001), as the film thickness increases, at about 30 nm a change from fully to partially strained has been induced, and a further annealing at 900 °C can fully relax the films. For LCMO/LSAT(001), however, due to the negligible lattice mismatch, even at 15 nm the films are almost fully relaxed. Correspondingly, for the fully relaxed LCMO films a paramagnetic to ferromagnetic transition at TC of about 260 K was observed, and for those partially relaxed, both the structure and magnetic transition are inhomogeneous, two thickness-dependent TC were detected for each film. The results show strong evidence that the transition temperature is correlated with the strain state in epitaxial LCMO films. [ABSTRACT FROM AUTHOR]

The process-induced domain evolution and asymmetric switching in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films have been studied by reciprocal space mapping, transmission electron microscopy, high-temperature x-ray diffraction, and the polarization-electric field hysteresis loop measurements. After annealing at reduced oxygen pressures, it was evidenced that an oxygen loss at the PZT bottom interface can occur at temperatures well below the Curie temperature TC, and more importantly, the oxygen loss can induce a large positive voltage offset and drive simultaneously the polydomain formation in the PZT films. Our results indicate that the structure evolution is correlated with the coercive voltage shift, and an oxygen-loss-related internal stress at the interface would be responsible for the large internal electric field in epitaxial PZT films. [ABSTRACT FROM AUTHOR]

Epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin-film capacitors with La0.7Sr0.3MnO3 (LSMO) electrodes have been grown on (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (001) substrates by pulsed-laser deposition. The process-induced imprint behavior in the ferroelectric capacitors was examined by in situ and ex situ annealing at various conditions. It was found that for the capacitors in situ annealed at reduced oxygen pressures, where the LSMO electrodes are stable, voltage offsets in the polarization-electric field hysteresis loops were observed only for those treated at temperatures higher than the Curie temperature. At lower temperatures, the oxygen loss may be suppressed by stresses arising primarily from the paraelectric-to-ferroelectric transformation. However, for the capacitors ex situ annealed at the same low temperature, large voltage offsets were induced due to the oxygen instability of the LSMO electrodes. We show evidence that the imprint is caused by oxygen loss at the PZT/LSMO interface, and closely related to the variation of the PZT structure. [ABSTRACT FROM AUTHOR]

Epitaxial Pb(Zr[sub 0.52]Ti[sub 0.48])O[sub 3]/La[sub 0.7]Sr[sub 0.3]MnO[sub 3](PZT/LSMO) and LSMO/PZT/LSMO heterostructures have been grown on LaAlO[sub 3](001) substrates by pulsed-laser deposition. Three types of ferroelectric capacitors, i.e., Pt/PZT/LSMO (A), LSMO/PZT/LSMO (B), and Pt/PZT/LSMO (C) have been fabricated, where the Pt electrode was sputter deposited onto as-grown (capacitor A) and in situ annealed (capacitor C) PZT/LSMO films, respectively. It is found that the LSMO/PZT/LSMO capacitor shows a low coercive field and good fatigue endurance up to 10[sup 10] switching cycles. Similar properties are also obtained for capacitor A. However, the capacitor C, with the PZT film in situ annealed at reduced oxygen pressures, exhibits higher switching voltages and starts to fatigue rapidly at about 10[sup 6] bipolar switching cycles. Lead deficiency at the surface of the annealed PZT films has been observed. Our results demonstrate that the fatigue performance of PZT/LSMO films, although affected greatly by the electrode configurations, is intrinsically determined by the interface property at the top electrode. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]