We report here synthesis of phase-pure magnetoelectric BiFeO3 thin films with controlled oxygen stoichiometry on Pt/TiO2/SiO2/Si substrate using pulsed-laser deposition technique. Saturated ferroelectric hysteresis loop has been observed in phase-pure and highly resistive BiFeO3 thin films. The dielectric response study of the films with temperature indicates an anomaly in dielectric constant ε(T), in the vicinity of Néel temperature (∼380 °C). This anomaly in ε(T) is explained as an influence of vanishing magnetic ordering on electric ordering of magnetoelectric BiFeO3 sample.

The polycrystalline La 1Ϫx Ce x MnO 3 manganites do not exist in single phase in bulk under the preparation conditions so far employed, but their polycrystalline and epitaxial films deposited by the pulsed laser deposition ͑PLD͒ technique form readily in single phase. The cerium oxide (CeO 2 ) remains partially unreacted when the bulk sample is prepared through the solid state reaction route. The resistivity of the bulk La 0.7 Ce 0.3 MnO 3 sample shows a broad metal insulator transition ͑MIT͒ clearly resolved into two peaks, suggesting the presence of a second ͑impurity͒ phase, which is identified as unreacted CeO 2 by the intensity analysis of the x-ray diffraction ͑XRD͒ data. However, when prepared as thin films by PLD, La 0.7 Ce 0.3 MnO 3 forms in single phase, as corroborated by the uniqueness and sharpness of the MIT peak and also by the XRD patterns of the polycrystalline films. We also performed a detailed study of the epitaxial films by a high-resolution XRD system with a four-circle goniometer and did not find any impurity phase. The magnetization data shows a very sharp transition followed by a sharp MIT in resistivity at the same temperature in the epitaxial thin film. These results suggest that PLD can be used as a useful technique to synthesize unconventional compounds, which do not form easily in bulk.

The hole-doped manganite La 0.7 Ca 0.3 MnO 3 and the electron-doped manganite La 0.7 Ce 0.3 MnO 3 undergo an insulator to metal transition at around 250 K, above which both behave as a polaronic semiconductor. We have successfully fabricated an epitaxial trilayer (La 0.7 Ca 0.3 MnO 3 /SrTiO 3 /La 0.7 Ce 0.3 MnO 3 ), where SrTiO 3 is an insulator. At room temperature, i.e. in the semiconducting regime, it exhibits asymmetric current-voltage (I-V) characteristics akin to a p-n diode. The observed asymmetry in the I-V characteristics disappears at low temperatures where both the manganite layers are metallic. To the best of our knowledge, this is the first report of such a p-n diode, using the polaronic semiconducting regime of doped manganites.

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In this letter, we report the improved magnetotransport properties of La0.7Sr0.3MnO3-borosilicate glass composite with different weight percents of glass. All the composites showed ferromagnetic nature at room temperature. The microstructure of these composites was seen using a scanning electron microscope. The microstructure was reconfirmed using spot energy dispersive x-ray analysis. We observe an enhancement of the low-field magnetoresistance (<200 Oe) at room temperature for the optimal composition of 25 wt % of glass. It is argued that glass layer separating the grain boundaries may be acting as barrier for spin-polarized tunneling, thereby enhancing the low-field magnetoresistance.