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Heterostructure composed of electron-doped high-Tc superconductor La1.89Ce0.11CuO4 (LCCO), ferroelectric Ba0.5 Sr0.5 TiO3 (BST) and colossal magnetoresistance (CMR) La0.67 Sr0.33 MnO3 (LSMO) thin films were deposited on the (001) SrTiO3 (STO) substrate by pulsed laser deposition method. The current-voltage measurement shows that the LCCO/BST/LSMO structure has strong rectification comparing to the LCCO/LSMO, LCCO/BST and BST/LSMO bilayer structures. The experiment indicates that both the BST and LCCO layers play important roles in the rectifying effect in the oxide heterostructures. We discuss the mechanism of their rectification based on the energy band bending as well as the depletion and the diffusion of the charge carriers at the interfaces. The growth conditions and the multilayer features as well as the properties of individual material in the heterostructures were also investigated. [ABSTRACT FROM AUTHOR]

Leakage current of Pt/(Ba0.7Sr0.3)TiO3 (BST)/YBa2Cu3O7-δ capacitors on a (001) SrTiO3 substrate was studied. By modeling a low-dielectric constant layer, a so-called dead layer, between the Pt/BST interface as a parasitic capacitor in series with the bulk layer capacitor, the leakage current of Pt/BST interface was well analyzed based on the modified Schottky emission equation. Furthermore, a two-step schematic energy band diagram is proposed to explain the carrier transport through the Pt/BST interface. [ABSTRACT FROM AUTHOR]

We investigated the structure and transport properties of GdBa[sub 2]Cu[sub 3]O[sub 7] films on SrTiO[sub 3](001) and NdGaO[sub 3](001). We found that the films can be grown pseudomorphically up to at least 42 nm thickness on SrTiO[sub 3] whereas the critical thickness is less than 14 nm for films on NdGaO[sub 3]. The carrier density of pseudomorphic films on SrTiO[sub 3] is tuned by the pseudomorphic stress field and films on SrTiO[sub 3] show higher T[sup *] and lower T[sub c] compared to films of the same thickness on NdGaO[sub 3]. For a 28 nm thick GdBa[sub 2]Cu[sub 3]O[sub 7] film on SrTiO[sub 3], the hole density per CuO[sub 2] plane is reduced to 0.12, compared to 0.16 for the optimally doped and stress-free RBa[sub 2]Cu[sub 3]O[sub 7]. The measured temperature dependence of J[sub c] can be understood and described by interface stress pinning. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Undoped and Fe-doped liquid encapsulated Czochralski (LEC) InP has been studied by Hall effect, current-voltage (I-V), and infrared absorption (IR) spectroscopy. The results indicate that a native hydrogen vacancy complex donor defect exists in as-grown LEC InP. By studying the IR results, it is found that the concentration of this donor defect in Fe-doped InP is much higher than that in undoped InP. This result is consistent with the observation that a much higher concentration of Fe[sup 2+] than the apparent net donor concentration is needed to achieve the semi-insulating (SI) property in InP. By studying the I-V and IR results of Fe-doped InP wafers sliced from different positions on an ingot, the high concentration of Fe[sup 2+] is found to correlate with the existence of this hydrogen complex. The concentration of this donor defect is high in wafers from the top of an ingot. Correspondingly, a higher concentration of Fe[sup 2+] can be detected in these wafers. These results reveal the influence of the complex defect on the compensation and uniformity of Fe-doped SI InP materials. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Single-phased, single-oriented thin films of Mn-doped ZnAs-based diluted magnetic semiconductor (DMS) Ba1-xKx(Zn1-yMny)2As2 (x = 0.03, 0.08; y = 0.15) have been deposited on Si, SrTiO3, LaAlO3, (La,Sr)(Al,Ta)O3, and MgAl2O4 substrates, respectively. Utilizing a combined synthesis and characterization system excluding the air and further optimizing the deposition parameters, high-quality thin films could be obtained and be measured showing that they can keep inactive-in-air up to more than 90 hours characterized by electrical transport measurements. In comparison with films of x = 0.03 which possess relatively higher resistivity, weaker magnetic performances, and larger energy gap, thin films of x = 0.08 show better electrical and magnetic performances. Strong magnetic anisotropy was found in films of x = 0.08 grown on (La,Sr)(Al,Ta)O3 substrate with their magnetic polarization aligned almost solely on the film growth direction. [ABSTRACT FROM AUTHOR]

Complex conductivity of FeSe0.5Te0.5 superconducting films has been investigated using backward-wave-oscillator spectroscopy in the terahertz frequency range. The normal state conductivity corresponds well to the lowfrequency limit of a Drude metal. In the superconducting state, the real part of the complex conductivity is not completely suppressed, indicating the existence of a strongly anisotropic gap. Weak features in the conductivity are consistent with the superconducting gap value close to 12 cm-1(1.5 meV). The experimental results are discussed within the framework of a two-gap model based on the s± symmetry of the order parameter. [ABSTRACT FROM AUTHOR]

Soil loss from unpaved rural roads contributes largely to watershed sediment yield. A road erosion model is therefore urgently needed to evaluate road erosion production. Field flow simulation experiments were conducted on unpaved loess roads under five flow rates and three slope gradients in order to quantify road surface hydraulics and develop soil detachment prediction models. The results showed that flow velocity was highly related to flow rate but generally independent of slope gradient. The hydraulic roughness of the road surface was much less titan that of cropland and was influenced significantly by relatively intensive erosion on steep slopes. Easily obtainable parameters such as flow rate and slope gradient could be used to estimate soil detachment accurately. Furthermore, power functions of chosen hydraulic parameters, (i.e., shear stress, stream power, and unit stream power) could be used to predict detachment rates. Among these parameters, flow shear stress was the best predictor. A detachment prediction model similar to that used in the WEPP model was proposed. Corresponding to the excess shear stress model in WEPP, loess road surface soil erodibility is 0.0066 s m-1 and critical shear stress is 3.25 Pa. [ABSTRACT FROM AUTHOR]

Underdoped electron-doped La2-xCexCuO4 (x=0.06-0.09) thin films were successfully grown and investigated for the transport properties in ab-plane. It was found that the in-plane resistivity ρab shows a semiconductor behavior when x=0.06, with increasing the Ce concentration to the optimal doping level, it changes to the two dimensional Fermi-liquid behavior. In the films with x≥0.08, a Kondo effect like scattering is observed in the low temperature range. [ABSTRACT FROM AUTHOR]

YBa2Cu3O7-δ/La0.67Ca0.33MnO3 heterostructures were fabricated and patterned to study the interfacial transport between a ferromagnet (FM) and a dx2-y2-wave superconductor. Zero bias conductance peaks (ZBCPs) in the differential conductance spectra were observed in the interface where a YBCO layer shows a mixed c- and a-axis orientation. In contrast, a zero bias conductance dip (ZBCD) was observed in the interface with a purely c-axis oriented YBCO layer. [ABSTRACT FROM AUTHOR]

High quality epitaxial thin films of FeSe1-xTe_x (x=0–1) have been successfully fabricated. Their superconducting transition temperatures are around 8–13 K. Microwave properties of a film (x=0.7) was studied by a sapphire dielectric cavity at 9.315 GHz. The cavity, which has a quality factor of 45000 in room temperature with TE011-mode, is specially designed for the measurement of small samples with the sapphire cylinder having a small hole in the center. Thin film samples with dimension of 1–2 mm can be put in the middle of the hole, supported by a very thin sapphire rod. The cavity is sealed in a vacuum chamber soaked in the liquid ^4He and the temperature of the thin sapphire rod (hence the sample) can be controlled from 1.6 K to 60 K with a stability about \pm1 mK. Temperature dependence of transmission response and Q-factors were measured by a network analyser (Agilent N5230C). The results showed a clear signature of multi-gap superconductivity. No evidences of existence of node in the energy gap were found as the normalized change in the surface reactance and the corresponding normalized change in the in-plane penetration depth have flat dependence at low temperatures. [ABSTRACT FROM AUTHOR]

Ferroelectric K0.5Na0.5NbO3 (KNN) thin film was epitaxially grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 substrate by pulse laser deposition. The crystallographic structure of KNN/LSMO was confirmed by x-ray diffraction. Interestingly, a dielectric relaxor feature was found in the temperature range 200–350 °C. The activation energies for relaxation and conduction of the films were found to be 1.87 and 0.63–0.71 eV, respectively. The mechanism for dielectric relaxation in KNN/LSMO structure was discussed under a thermally activated process. The remnant polarization and coercive field of the films were 21.3 μC/cm2 and 91 kV/cm, respectively. [ABSTRACT FROM AUTHOR]

The exchange bias effect has been observed in the superlattices consisting of ferromagnetic La0.67Sr0.33MnO3 and nonmagnetic insulating SrTiO3 layers. It is found that the exchange field shows an oscillatory decay with a period of ∼12 unit cells and approaches to a constant value of -100 Oe when the SrTiO3 thickness is increased. The tunneling current also displays a nonmonotonic decrease with the SrTiO3 thickness. These observations can be discussed on the basis of the interlayer exchange coupling between La0.67Sr0.33MnO3 layers via the spin-polarized electrons tunneling across the SrTiO3 spacers. [ABSTRACT FROM AUTHOR]

The magnetization and electrical transport in the superlattices consisting of ferromagnetic La0.67Sr0.33MnO3 and nonmagnetic insulating SrTiO3 layers have been investigated. A significant displacement of the hysteresis loop along the field axis is observed when the sample is field-cooled through the blocking temperature TB. The strength of displacement, termed as exchange field HE, is found to exponentially decay with temperature. The magnetoresistance in field-cooling process is obviously enhanced compared to that in zero-field-cooling process. The existence of the disordered spin state at the interface is suggested to be the origin of such phenomena. [ABSTRACT FROM AUTHOR]

The authors report the formation of the metallic oxide p-I-n junctions with the ferroelectric (Ba,Sr)TiO3 (BST) as the barrier. The junctions with different thicknesses of BST are investigated. With appropriate thickness, the junctions possess definite parameters, such as the negligible reversed current density (<=10-7 A/cm2), large breakdown voltage (>7 V), and ultrahigh rectification (>2×104) in the bias voltage ≤=2.0 V and temperature range from 5 to 300 K. It is under consideration that the built-in field V0, the ferroelectric reversed polarized field Vrp, and the resistivity of the BST layer together decide the transport properties of the junctions [ABSTRACT FROM AUTHOR]

Epitaxial Ba0.15Zr0.85TiO3 (BZT) ferroelectric thin films with (001), (011), and (111) orientations were, respectively, grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 substrates by pulsed laser deposition method. The dc electric-field dependence of permittivity and dielectric loss of (001)-, (011)-, and (111)-oriented BZT/LSMO heterostructures obeys the Johnson formula, and the ac electric-field dependence of that obeys the Rayleigh law under the subswitching field region. The anisotropic dielectric properties are attributed to the higher mobility of the charge carriers, the concentration of mobile interfacial domain walls, and boundaries in the (111)-oriental films than in the (110)- and (100)-oriented films. [ABSTRACT FROM AUTHOR]

We use magnetism and specific heat measurements to investigate the hexagonal Mn-rich YMnO3. It is found that upon cooling from a high temperature, the compound first orders antiferromagnetically at TN∼72 K and then undergoes a re-entrant spin glass (RSG) transition at TSG∼42 K. This RSG behavior results from the competition between the ferromagnetic interaction and the antiferromagnetic interaction, which is related to the intrinsic geometric magnetic frustration in this system. [ABSTRACT FROM AUTHOR]

Studies the use of allogeneic peripheral blood stem cell transplantation in the treatment of leukemia in China. Subjects and procedures; Results; Discussion.

Perovskite oxide junctions of p-type colossal magneto-resistance material La0.67Sr0.33MnO3 (LSMO), strontium titanate insulator SrTiO3 (STO) and n-type high-Tc superconductor La1.89Ce0.11CuO4 (LCCO) were deposited on STO (001) substrates by the pulsed laser deposition method. The current–voltage (I–V) characteristics were measured at room temperature and pronounced rectifying characteristics were observed. The trilayer junctions with different thicknesses of the middle STO insulator were investigated and the measurement exhibits a remarkable insulator thickness dependence in their I–V characteristics. We attribute the rectification of the trilayer junctions to the interfaces between different materials by energy band analysis. [ABSTRACT FROM AUTHOR]

A ferroelectric and colossal-magnetoresistant material with a Ba0.5Sr0.5TiO3 (BST)/La0.67Sr0.33 MnO3 (LSMO) heterostructure was deposited epitaxially on (001) LaAlO3 substrates through pulsed laser deposition. Measurements of the magnetic and ferroelectric properties show no obvious degradation of the LSMO layer after BST film deposition. For the BST film, as the temperature decreases from 300 to 20 K, both the remanent polarization and the coercive field increase monotonously up to 5.7 µC cm−2 and 63.7 kV cm−1, respectively. Meanwhile, the temperature dependence of the spontaneous polarization shows a second-order ferroelectric phase transition, and the Curie temperature is estimated to be about 220 K. Furthermore, in the temperature range from 20 to 300 K, the dielectric constant (E = 0) and the dielectric tunability (E = 200 kV cm−1) exhibit similar temperature dependences, and show maximum values of 1252 and 45.3% at 200 K, respectively. [ABSTRACT FROM AUTHOR]