Search

Abstract: (K,Na)NbO3 ferroelectric films were grown on LaNiO3 coated silicon substrates by RF magnetron sputtering. The conductive LaNiO3 films acted as seed layers and induced the highly (001) oriented perovskite (K,Na)NbO3 films. Such films exhibit saturated hysteresis loops and have a remnant polarization (2P r) of 23μC/cm2, and coercive field (2E c) of 139kV/cm. The films showed a fatigue-free behavior up to 109 switching cycles. A high tunability of 65.7% (@300kV/cm) was obtained in the films. The leakage current density of the films is about 6.0×10−8 A/cm2 at an electric field of 50kV/cm. [Copyright &y& Elsevier]

Abstract: Ba0.6Sr0.4TiO3 (BST)/MgO columnar composites are fabricated via the spark plasma sintering (SPS) method. The microstructure, dielectric and tunable properties of columnar composites are investigated. The unmodified BST Curie temperatures with the increase of MgO addition indicate a sufficient suppression of ions interdiffusion between the two phases. The dielectric constant is decreased from 7000 to 3800 when MgO weight ratio is up to 15% while the tunability still stays at high level over 45%. The coefficient of the dielectric nonlinearity β shows a growing trend with increasing MgO content. The experimental results are in agreement with the theoretical prediction and confirm that if the composite is fabricated in columnar model, a reduction of dielectric constant without a deterioration of tunability could be achieved, which make them useful for potential tunable device applications in wireless communication system. [Copyright &y& Elsevier]

Abstract: The frequency, electric field cycling and temperature dependences of the polarization–electric field (P–E), strain–electric field (S–E) loops in poled Mn-doped 0.05Pb(Mn1/3Sb2/3)O3–0.50PbZrO3–0.45PbTiO3 ceramics have been investigated. The P–E and S–E loops are strongly asymmetric corresponding to the presence of an internal bias field E i after poling and aging, indicating that the domain walls are strongly pinned by preferentially oriented defect dipoles formed by the acceptor dopant ions (Mn2+/Mn3+) and O2− vacancies. Whereas, the loops exhibit a tendency of changing from asymmetric shapes to normal symmetric ones with increasing electric field amplitude or decreasing frequency. Repeated electric field cycling as well as high temperature results in a similar effect. Meanwhile, the E i reduces consequently, providing evidence of domain depinning or internal bias field relaxation. It is suggested that the reorientation of the defect dipoles and depinning of domain walls arising from high temperature or electric field cycling are responsible for this extrinsic internal bias field relaxation process. [Copyright &y& Elsevier]

The correlation between films thickness and the physical properties (such as magnetic, magnetotransport properties) has been investigated in 5 nm and 160 nm La 0.7 Sr 0.3 MnO 3 (LSMO). The films were deposited on (100) SrTiO 3 (STO) substrates by chemical solution deposition method. High-resolution X-ray diffraction (HRXRD) and high-resolution transmission electron microscopy have been used to estimate the epitaxial structure and the change of strain. Both of the films are grown on STO substrates with coherent interfaces. The thinner sample has fully strained while the thicker film is partially strain relaxation. With decreasing film thickness from 160 to 5 nm, both of the T C and T MI strongly depressed. The strain and limitation of the spin fluctuations by the film thickness are the main origins of the Tc lowering. The MR value of S1 is much larger than that of S2 at 300 K. It can be elucidated by the existence of magnetic polarons around T C and spin fluctuations in the interface between the film and the substrate. [ABSTRACT FROM AUTHOR]

La 0.7 Ca 0.3 MnO 3 (LCMO)/La 0.7 Sr 0.3 MnO 3 (LSMO) multilayer films have been successfully prepared on (100) oriented SrTiO 3 substrates by chemical solution deposition method. The relationship between the multilayer structure and physical properties was systematically studied. X-ray diffraction (HRXRD) patterns of θ−2θ scan show that both of the films have perfect crystalline orientation. Reciprocal space maps (RSM) of the multilayer films show that the multilayer films are epitaxial growth and fully strained. Independent ferromagnetic - paramagnetic transition of LCMO and LSMO layer are visible as a function of the temperature, which indicates that the magnetization of the individual layers can rotate independently of each other. The maximum value of absolute MR is increased slightly as the layer number increasing. It can be attributed to the spin-polarized tunneling which is associated with magnetic domain rotation at the interface. [ABSTRACT FROM AUTHOR]