No abstract

We report a technique to prepare top and bottom oxide electrodes of LaNiO3 (LNO) for lead zirconate titanate (PZT) films using a chemical solution deposition. LNO/PZT/LNO sandwich structures were prepared on platinized silicon by spin coating combined with rapid thermal annealing. Pt dots were sputtered on top of LaNiO3 film to serve as protective masks during etching of the uncovered LaNiO3 layer using dilute hydrochloric acid. For comparison, Pt/PZT/Pt capacitors were also prepared using the same processing conditions. Electrical measurements were carried out on both Pt/LNO/PZT/LNO/Pt and Pt/PZT/Pt structures. The remnant polarizations and coercive fields for these two capacitors are 17.4 and 21.4μC∕cm2, 71 and 81.5kV∕cm respectively at 5V. The leakage current density for the Pt/LNO/PZT/LNO/Pt structure is about 1.38×10−6A∕cm2 at 5V, which is lower than that of PZT deposited on Pt electrode. After 109 bipolar switching cycles, no significant change in remnant polarization was observed in the Pt/LNO/PZT/LNO/Pt capacitor, in comparison to the Pt/PZT/Pt capacitor which lost more than 50% of its original remnant polarization.

Pb ( Nb 0.02 Zr 0.2 Ti 0.8 ) O 3 thin films with thickness of 900nm were spincoated on platinized silicon substrate using the sol–gel method. X-ray diffraction and field emission scanning electron microscopy show that the films are highly a-axis-oriented with columnar structure. A large remnant polarization (Pr+) ∼92.2μC∕cm−2 was observed for as-grown films. The coercive field (Ec+) for these films was 159.3kV∕cm. Good pyroelectric properties are obtained as a result of large remnant and spontaneous polarization and their strong temperature dependence. The pyroelectric coefficient and figure of merit at room temperature (22°C) are 10.8×10−4Cm−2K−1 and 2.34×10−5Pa−1∕2, respectively.

Large high-purity single crystals of FeTiO3 with ilmenite structure have been grown from a stoichiometric melt of Fe2O3 and TiO2 under an inert atmosphere using the modified Czochralski technique. Susceptibility and x-band paramagnetic resonance studies have been performed. Susceptibility measurements indicate a Néel temperature ∼59 K. The paramagnetic resonance spectrum for magnetic field perpendicular to the crystal c axis consists of a portion of a single, very intense approximately Lorentzian absorption line with its peak at about 600 G and half width at half maximum almost 1200 G. The absorption extends to zero magnetic field. For magnetic field approximately parallel to the c axis, the paramagnetic absorption is much smaller and may be considered a superposition of two approximately Lorentzian line shapes. The magnetic resonance measurements indicate a weak temperature dependence and large angular anisotropy.

The morphology, structure, and magnetic properties of the magnetic semiconductor ceramic Ilmenite-Hematite (IH), (1Àx)Fe-TiO 3 -xFe 2 O 3 , were studied as a function of the composition x. The magnetic ordering temperatures that we observed were consistently higher than those reported previously and were, for most of the composition range, above room temperature. We rule out the formation of Fe clusters as the origin of the magnetic properties. These magnetic properties of IH ceramics, in combination with their semiconducting characteristics, render them promising for spin-electronic applications. 1601J ournal