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A trilayer system (CoFe/Bi/Co) with bismuth as a spacer layer was synthesized using dc sputtering at room temperature. Magnetization studies show that the interlayer coupling between two ferromagnetic electrodes oscillates with the thickness of Bi spacer layer at room temperature, as seen in most metallic spacers, but it has a much longer period, which is estimated to be 180 to 200 Å. Furthermore, the range of interlayer coupling between two ferromagnetic layers separated by Bi spacer can be extended up to 500 Å. As the measuring temperature is reduced, the strength of interlayer coupling increases and varies with Bi thickness in a similar way, but the oscillation amplitude decreases. [ABSTRACT FROM AUTHOR]

We report transport, magnetization, and transmission-electron-microscopic studies of La[sub 1-x]Ba[sub x]MnO[sub 3]/SrTiO[sub 3] thin films grown by pulsed-laser deposition. The metal–insulator transition is remarkably sharp, and the high value of the temperature coefficient of resistivity is significantly relevant for the required value for the infrared imaging applications. We have demonstrated that the strain-induced property can be tuned and stabilized in La[sub 1-x]Ba[sub x]MnO[sub 3] films simply by changing the doping level (La/Ba ratio) and addition of metal ions (Ag) for applications at desirable temperature regime close to room temperature. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

La0.60Sr0.40MnO3 (LSMO) thin films of varying thickness from 12 to 55 nm were deposited using the pulsed-laser deposition technique onto single-crystalline SrTiO3 (STO) and STO-buffered Si substrates. The Tc of LSMO films grown on STO-buffered Si substrates decreases faster than films directly grown on STO with decreasing film thickness. The LSMO/STO film with thickness of 55 nm shows Tc at about 360 K, which is close to the bulk value, whereas Tc LSMO film on STO-buffered Si film of similar thickness is reduced to 320 K. This difference is attributed to the strain and interfacial disorders in LSMO film on STO/Si. The film surface morphology is influenced by the film thickness. Oxygenation of LSMO films on STO-buffered Si affects the Tc minimally but improved the overall magnetization of the films due to better oxygenation, which is also the case for postannealing the sample at elevated temperatures. The thermomagnetic history effects observed in LSMO films of STO-buffered Si indicate the presence of inhomogeneity, mostly at the interface, which influences the magnetic properties significantly. [ABSTRACT FROM AUTHOR]

We report on the fabrication and tunneling characteristics of pulsed-laser deposited LaSrMnO (LSMO)/PbZrTiO(PZT)/LSMO/SrTiO3 multilayers, using PZT layer as a tunnel barrier. The trilayer films show magnetic onset at about 360 K with ferromagnetic hysteresis at room temperature. The microscopic studies show that the effective barrier thickness is reduced due to the presence of defects in the barrier region. Our results suggest that the asymmetric deformation of the barrier potential profile induced by the ferroelectric polarization of PZT influences the tunneling characteristics and can be used for electrically controlled readout in quantum-computing schemes. [ABSTRACT FROM AUTHOR]

The authors report the fabrication of p-n junctions, consisting of n-type SrTiO3 or BaTiO3 and p-type Si substrates, by the pulsed-laser deposition technique. The BaTiO3/Si junction exhibits excellent rectifying behavior and significantly reduced leakage current at 300 K exceeding breakdown voltage of -25 V with leakage current <0.5 μA, while SrTiO3/Si with an interfacial layer shows moderate junction characteristics. It was demonstrated that the BaTiO3/Si grown at an optimum growth temperature of 650 °C displayed superior performance which is promising for electronic devices. Both junctions show photocurrent at 300 K due to electron injection following the photoexcitation of n-type perovskite. [ABSTRACT FROM AUTHOR]

We report significant enhancement of magnetoresistance (MR) in melt-processed La[sub 0.67]Ca[sub 0.33]MnO[sub 3] (LCM) and in Ho-doped LCM samples. The LCM system exhibits surprising enhancement of metal-insulator transition (T[sub IM]) that coincides with the Curie transition temperature (T[sub c]), T[sub IM]approx. T[sub c], illustrating the enhanced percolative transport and spin-polarization through grain boundaries. Surprisingly, 1 mol % of addition of Ho enhances T[sub c] of ∼70 K with remarkable colossal MR. The nanoscale Ho distribution is consistent with the magnetic inhomogeneity-induced MR due to phase segregation in Ho-doped sample whereas charge-segregation picture is valid for undoped LCM. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report measurements of the resistivity and magnetization of high-quality melt-processed La[sub 0.67]Ca[sub 0.33]MnO[sub 3] (LCM) and Sr-doped LCM materials that exhibit a sharp and enhanced metal–insulator transition (T[sub MI]) with significant colossal magnetoresistance (CMR) and two competing magnetic phases in the vicinity of T[sub MI]. Our results can well be explained using percolation in combination with the phase-separation scenario proposed for CMR. We propose that the spin polarization through grain boundaries and the enhanced grain connectivity between the ferromagnetic domains facilitate better percolation through a junction and filament-like resistor network. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have performed magnetic and transport measurements on La[sub 0.67]Ca[sub 0.33]MnO[sub 3] polycrystalline and partially melted samples. The magnetization and resistance decrease as sintering temperature is increased. The insulator-to-metal transition temperature is remarkably enhanced in the partially melted sample, enabling its possible applications at room temperature. The microscopic studies in melt samples show an excellent connectivity between grains, suggesting the enhancement of percolative transport by opening new conduction channels and the disappearance of magnetic phase boundary at elevated temperature by the ordering of Mn spins blocked at the grain boundary of sintered samples. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]