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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Properties of tree rings in LSST sensors

Images of uniformly illuminated sensors for the Large Synoptic Survey Telescope have circular periodic patterns with an appearance similar to tree rings. Furthermore, these patterns are caused by circularly symmetric variations of the dopant concentration in the monocrystal silicon boule induced by the manufacturing process. Non-uniform charge density results in the parasitic electric field inside the silicon sensor, which may distort shapes of astronomical sources. Here, we analyzed data from fifteen LSST sensors produced by ITL to determine the main parameters of the tree rings: amplitude and period, and also variability across the sensors tested at Brookhaven National Laboratory. Tree ring pattern has a weak dependence on the wavelength. But the ring amplitude gets smaller as wavelength gets longer, since longer wavelengths penetrate deeper into the silicon. Tree ring amplitude gets larger as it gets closer to the outer part of the wafer, from 0.1 to 1.0%, indicating that the resistivity variation is larger for larger radii.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

How Excitation Conditions Alter the Afterglow Characteristics of CsI:Tl,Sm Microcolumnar Films

Combining high light output with the microcolumnar structure, the CsI:Tl films significantly reduce the need for painful tradeoff between thickness (hence, stopping power) and spatial resolution. But both films and monocrystals share two important deficiencies that hinder their use in many high-speed imaging and computed tomography applications: a persistent afterglow and hysteresis. These properties receive the primary attention of this investigation. In our earlier work, we reported that codoping with Sm 2+ brings about a significant reduction in the afterglow of CsI:Tl. Here, focusing on the microcolumnar films, we examine this afterglow-suppressive effect over a wide range of exposure times, from milliseconds to seconds, and at temperatures between 0 °C and 60 °C. Our measurements reveal well-defined dependences on both parameters. At room temperature (20 °C), defined as the normal operating condition, a 10-ms X-ray pulse leaves an afterglow from the standard (Sm-free) CsI:Tl of about 1% at 2 ms after the end of the pulse, changing little as a function of pulselength. Doping with Sm 2+ , however, reduces that afterglow by at least an order of magnitude, although somewhat less so after longer (100 and 1000 ms) pulses. When we change the temperature, however, we find markedly different behavior. Here, we find that a temperature increase of only 60°, without changing the pulselength, cuts the afterglow of standard CsI:Tl films by a factor of 20. However, films of codoped CsI:Tl,Sm, whose afterglow has already been suppressed by the presence of Sm 2+ , show much less change as a function of either temperature or pulse duration. It is the presence of Sm 2+ that makes the biggest difference. As for hysteresis, we again see an improvement, with the performance of the codoped CsI:Tl,Sm films bettering that of the standard (Sm-free) films. After an exposure of 300 mR, the change in light output falls to within 1% of the original after 1 min, whereas standard CsI:Tl films require 30 min to reach the same level.

42 ENGINEERING↗
DOE OSTI2012

Cation ordering and physicochemical characterization of the quaternary diamond-like semiconductor Ag[subscript 2]CdGeS[subscript 4]

The quaternary diamond-like semiconductor, Ag2CdGeS4, was synthesized via high-temperature solid-state synthesis as well as structurally and physicochemically characterized. Single crystal X-ray diffraction provided a model for Ag2CdGeS4 in the orthorhombic, noncentrosymmetric space group Pna21 with a=13.7415(8) {angstrom}, b=8.0367(5) {angstrom} and c=6.5907(4) {angstrom}, in contrast to a previously published model in Pmn21 from the Rietveld analysis of laboratory X-ray powder diffraction data. The Pna21 space group is supported by the Rietveld analysis of synchrotron X-ray powder diffraction data. Differential thermal analysis suggests that Ag2CdGeS4 exists in two polymorphs. Optical diffuse reflectance UV/vis/NIR spectroscopy indicates that the orange compound is a semiconductor with a band gap of 2.32 eV. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy were used to further characterize the material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2}

Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a=12.2261(20) Angstrom-Sign , b=10.7447(20) Angstrom-Sign , c=8.4754(17) Angstrom-Sign and {beta}=110.288(30) Degree-Sign (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge){sub n}. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a=b=5.9874(6) Angstrom-Sign and c=15.1178(19) Angstrom-Sign . The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{proportional_to}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures. - Graphical abstract: The compounds Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are obtained from reactions of Yb and Ge in excess liquid gallium. Highlights: Black-Right-Pointing-Pointer Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are two new polygallides. Black-Right-Pointing-Pointer The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was established using neutron diffraction data. Black-Right-Pointing-Pointer YbGa{sub 4}Ge{sub 2} is one of the rare polar intermetallic compounds. Black-Right-Pointing-Pointer The physical properties of Yb{sub 3}Ga{sub 7}Ge{sub 3} point to a Fermi-liquid regime at low temperature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Gallium Pnictides of the Alkaline Earth Metals, Synthesized by Means of the Flux Method: Crystal Structures and Properties of CaGa[subscript 2]Pn[subscript 2], SrGa[subscript 2]As[subscript 2], Ba[subscript 2]Ga[subscript 5]As[subscript 5], and Ba[subscript 4]Ga[subscript 5]Pn[subscript 8] (Pn = P or As)

The focus of this paper is on the structural characterization of the new Zintl phases CaGa{sub 2}P{sub 2}, CaGa{sub 2}As{sub 2}, SrGa{sub 2}As{sub 2}, and Ba{sub 2}Ga{sub 5}As{sub 5}, and the solid solution (Ba{sub 0.85(1)}Sr{sub 0.15}){sub 2}Ga{sub 5}As{sub 5}, all of which were synthesized from molten metal fluxes.CaGa{sub 2}P{sub 2}, CaGa{sub 2}As{sub 2}, and SrGa{sub 2}As{sub 2} have layered structures with polyanionic layers made of ethane-like Ga{sub 2}P6 and Ga{sub 2}As6 motifs fused through common edges; the polyanionic substructure in Ba{sub 2}Ga{sub 5}As{sub 5} consists of condensed Ga{sub 2}As6 units and GaAs{sub 4} tetrahedra. Ba{sub 4}Ga{sub 5}P{sub 8} and Ba{sub 4}Ga{sub 5}As{sub 8}, another pair of new compounds with channel-like 3D structures, were also synthesized from metal fluxes, and their structures were established from single-crystal X-ray and synchrotron powder diffraction. They are based on GaP{sub 4} and GaAs{sub 4} tetrahedra, with parts of their structures being heavily disordered. The electronic structures computed with the linear muffin-tin orbital (LMTO) method are discussed as well, alongside the thermopower and the electrical conductivity, measured on single crystals of Ba{sub 2}Ga{sub 5}As{sub 5} and the solid solution (Ba{sub 0.85(1)}Sr{sub 0.15}){sub 2} Ga{sub 5}As{sub 5}. They demonstrate that such an approach would be an effective way to fine-tune the transport properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Spectra and Kinetics of YAG:0.5%Er{sup 3+} Radiation Under Pulsed Laser Thermal Excitation

The dependences of single-crystal YAG:0.5%Er{sup 3+} spectra in the range 200–1700 nm and the kinetics of the integrated emission on the excitation-energy density W of a single CO{sub 2}-laser pulse of ~100 ns FWHM duration at λ{sub ex} = 10.6 μm were investigated experimentally. The spectra changed qualitatively when W exceeded the generation threshold W{sub t} of laser plasma near the single-crystal surface. The YAG:0.5%Er{sup 3+} spectra at W < Wt were represented by peaks of selective emission (SE) of Er{sup 3+} multiplets on the continuous spectrum background. New emission peaks and additional background corresponding to emission spectra in a laser-induced air plasma with intensities much higher than the SE peaks appeared due to air ionization near the crystal surface at W > W{sub t}. Oscillograms of the integral emission in the range 600–1700 nm were characterized by a pulse-front duration of τ{sub f} = 1.0–1.6 μs and a decay time τ{sub d} ≈ 2.5 μs if W changed by one order of magnitude. The kinetics of the integrated emission intensity were explained by calculating the single-crystal temperature and the populations of Er{sup 3+} energy levels during conversion of thermal energy into SE during unsteady energy transfer by internal radiation and thermal conductivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

YAG:Er{sup 3+}, CaF{sub 2}:Er{sup 3+}, and Er{sub 2}O{sub 3} Emission Spectra Under Laser and Laser Thermal Excitation

Experimental luminescence and selective-emission (SE) spectra of YAG:Er{sup 3+} (10 at.%) and CaF{sub 2}:Er{sup 3+} (1 at.%) single crystals and Er{sub 2}O{sub 3} polycrystal under laser and laser thermal excitation of the Er3+-ion multiplets are compared. Luminescence spectra under resonant excitation are determined by multiplet population relaxation with the corresponding radiative and nonradiative probabilities. The form of the SE spectra is determined by the thermal population of the multiplets and the probabilities of only radiative transitions. The SE band at 800 nm ({sup 4}I{sub 9/2} → {sup 4}I{sub 15/2}) is an indicator of high-temperature thermal emission of Er{sup 3+} ions. The absence of this band in luminescence spectra is explained by the short lifetime of the τ({sup 4}I{sub 9/2}) level of 53 ns at T = 300 K.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of a Nitrogen Impurity on the Fundamental Raman Band of Diamond Single Crystals

The effect of nitrogen defects in natural and synthetic diamond single crystals on the position and half-width of the fundamental Raman band was investigated. Samples containing the main types of nitrogen lattice defects at impurity contents of 1–1500 ppm were studied. The parameters of the Stokes and anti-Stokes components in Raman spectra of crystals situated in a cell with distilled water to minimize the influence of heating by the exciting laser radiation were analyzed to determine the effect of a nitrogen impurity in the diamond crystal lattice. It was shown that an increase of impurity atoms in the crystals in the studied concentration range resulted in broadening of the Raman band from 1.61 to 2.85 cm{sup –1} and shifting of the maximum to lower frequency from 1332.65 to 1332.3 cm{sup –1}. The observed effect was directly proportional to the impurity concentration and depended on the form of the impurity incorporated into the diamond lattice. It was found that the changes in the position and half-width of the fundamental Raman band for diamond were consistent with the magnitude of crystal lattice distortions due to the presence of impurity defects and obeyed the Gruneisen law.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structure and Optical Properties Of LiNbO{sub 3}:В Crystals Grown from Charges of Different Origins

It was shown that, without entering the structure of the crystal, boron can change the structure of the melt and have a significant effect on the fine features of the structure and the physical characteristics of lithium niobate crystals. Crystals grown from a charge doped with boron by the direct solid-phase method have a stronger photorefractive effect and a smaller forbidden band width than crystals grown from the re-extract doped homogeneously with boron at the niobium pentoxide extraction stage.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis, Crystal Structure, Hirshfeld Surface Analysis, and Physicochemical Study of an Anhydrous Organic Acidic Cyclohexaphosphate

The new organic–inorganic hybrid [5-Cl-2-(CH{sub 3})C{sub 6}H{sub 3}NH{sub 3}]{sub 4}H{sub 2}P{sub 6}O{sub 18} has been synthesized by the slow evaporation method. X-ray diffraction on a single crystal shows that this acidic cyclohexaphosphate crystallized in the monoclinic space group C{sub 2/c} with a = 33.89(11) Å, b = 9.16(16) Å, c = 13.68(3) Å, β = 91.35(2)°, V = 4244.9(19) Å{sup 3} and Z = 4. {sup 31}P MAS-NMR and {sup 13}C CP/MAS-NMR results are in accordance with X-ray findings. Fluorescent study shows the blue photoluminescence. Furthermore, FT-IR analysis was studied and the complete vibrational assignments were done. Intermolecular interactions were analyzed using Hirshfeld surface analysis and the associated 2D fingerprint plots.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Boundary Current Response in Ba{sub 0.34}K{sub 0.64}Fe{sub 2}As{sub 2} Single Crystal Probed by Non-resonant Microwave Absorption

Non-resonant microwave absorption (NRMA) in superconducting materials has become a new experimental technique to probe and understand superconducting materials. For example, cuprate superconductors are well studied with this technique. At the same time, the technique is also evolving. This NRMA technique has been used to study magnetic shielding effects/boundary current in Ba{sub 0}.{sub 34}K{sub 0}.{sub 64}Fe{sub 2}As{sub 2} (BaK122) single crystals of iron pnictide superconducting sample measured at 9.4 GHz below T{sub c} (4.2–32 K). It has been observed that a small modulation field used in NRMA experiment yields the boundary current response. We have established that the boundary current response depends on both the modulation amplitude and the temperature. At high modulation field amplitudes and temperatures close to T{sub c}, the boundary current response gets suppressed and the flux-modulated response dominates. At low temperatures far away from T{sub c}, only the boundary current response dominates.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Angular-Dependent Vortex Pinning Properties of YBa{sub 2}Cu{sub 3}O{sub 7−δ}/Y{sub 2}O{sub 3} Quasi-Multilayers

A series of quasi-multilayers of YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO)/Y{sub 2}O{sub 3} specifically 70 × (m YBCO/n Y{sub 2}O{sub 3}) were prepared on SrTiO{sub 3} single crystal using pulsed-laser deposition (PLD) with a controlled deposition pulses of m = 40 and n = 2, 5, and 10 for YBCO and Y{sub 2}O{sub 3}, respectively. The x-ray diffraction patterns indicate that all the present quasi-multilayers exhibit good c-axis orientation. The angular dependence of critical current density (J{sub c}) on applied magnetic field directions are systemically measured to study the anisotropic vortex pinning performances for those quasi-multilayers. It is revealed that compared with the pure YBCO films, the quasi-multilayers with n = 2, i.e., a proper constituent pulse of Y{sub 2}O{sub 3}, exhibits the enhanced vortex pinning abilities in all angles between c-axis orientation and the applied magnetic field direction. As well, such a quasi-multilayer film (n = 2) shows the higher lift factor J{sub c}(Θ)/ J{sub c}(90°) and much better vortex pinning properties at high fields and high temperatures, showing promising potential for coated conductor application.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Optimization of the Dy Content in Single Crystalline GdBCO Bulk Superconductors Fabricated in Air Via Top-Seeded Infiltration Growth Process

Single-crystalline bulk GdBa{sub 2}Cu{sub 3}O{sub 7−δ} (GdBCO) superconductors were fabricated with top-seeded infiltration-growth technique (TSIG) in air by adding the different amounts of Dy{sub 2}BaCuO{sub 5} (Dy-211) particles (5, 10, 15, 20, 25, 30, 35, and 40 wt%). All the samples show superconducting critical temperature at ∼93 K with sharp transition irrespective of the chemical composition. X-ray diffraction measurements confirmed that all the samples were single domain with high alignment. Microstructural studies through scanning electron microscopy showed that TSIG-processed GdBCO samples contained 211 phase particles of two different sizes, i.e., ∼2–4 and ∼10 μ m. The addition of Dy-211 phase particles led to a significant enhancement of critical current density (J{sub c}) at 77 K. GdBCO superconductor with the addition of 20 wt% of Dy-211 showed the highest J{sub c} of 45.5 kA/cm {sup 2} at 77 K and self field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Dependence of Catalytic Activity of Nanocrystalline Nickel Ferrite on Its Structural, Morphological, Optical, and Magnetic Properties in Aerobic Oxidation of Benzyl Alcohol

Nanocrystalline nickel ferrite spinel, NiFe{sub 2}O{sub 4}, with average crystallite size of 23.98 and 19.76 nm were successfully synthesized under sol–gel method (SGM) and microwave method (MM) conditions without using any surfactant or otherwise structure-directing (oxalic acid as the fuel) agents. Powder x-ray diffraction, high-resolution scanning electron microscopies indicate that single-crystalline nanoparticles are well-dispersed in the nickel ferrite. The elemental investigation of nickel ferrite was attained from energy-dispersive x-ray (EDX) analysis. Their optical properties (diffuse reflectance spectroscopy and photoluminescence) were described in depth in relative with their structural characteristics and the functionalization performance. After the magnetic measurements, samples showed a ferromagnetic behavior and the magnetization (Ms) value of NiFe{sub 2}O{sub 4}-MM is higher, i.e., 59.33 emu/g than NiFe{sub 2}O{sub 4}-SGM (50.12 emu/g). The magnetic properties could be further changed by controlling the shape, size, and crystallinity of the nanocrystals. Determination of concentration NiFe{sub 2}O{sub 4} ions’ average number of atoms per nanoparticle was calculated by the new method as follows. Consequently, the designated procedure improves catalytic activity of nickel ferrite powders in aerobic oxidation of benzyl alcohol and catalytic reactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic and Transport Properties of Co{sub 1+δ}Sb Single Crystals

For some 3d transition-metal monopnictides, their physical properties are strongly affected by interstitial 3d transition-metal atoms, such as Fe{sub 1+δ}Sb, in which the electrical transport, magnetic properties and carrier concentrations have strong dependence on the composition of interstitial Fe (Shiomi et al. Phys. Rev. Lett. 108(5), 056601 2012), Therefore, it is important to study the influence of interstitial Co on the physical properties of Co{sub 1+δ}Sb. Here, the magnetic and transport properties have been studied on Co{sub 1.05}Sb single crystals. The magnetic and electrical transport measurements reveal that stoichiometric CoSb is a nonmagnetic metal. The interstitial Co in this compound exhibits a paramagnetic behaviour and weak antiferromagetic correlations. However, it has no effect on transport properties. A very low magnetoresistance (≤ 0.2%) was observed under the magnetic field up to 14 T, which suggests that Co{sub 1+δ}Sb could be a potential material of electronic devices for the application at a high magnetic field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Local Noncentrosymmetric Structure of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+y} by X-ray Magnetic Circular Dichroism at Cu K-Edge XANES

The two-dimensional Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+y} (Bi2212), the most studied prototype cuprate superconductor, is a lamellar system made of a stack of two-dimensional corrugated CuO{sub 2} bilayers separated by Bi{sub 2}O{sub 2+y}Sr{sub 2} O{sub 2} layers. While the large majority of theories, proposed to interpret unconventional high T{sub c} superconductivity in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+y}, assume a centrosymmetric tetragonal CuO{sub 2} lattice for the [CuO{sub 2}]Ca[CuO{sub 2}] bilayer, here, we report new compelling results providing evidence for local noncentrosymmetric symmetry at the Cu atom. We have measured polarized Cu K-edge XANES (X-ray absorption near-edge structure) and the K-edge X-ray magnetic circular dichroism (XMCD) of a Bi2212 single-crystal near-optimum doping. The Cu K-edge XMCD signal was measured at ID12 beamline of ESRF with the k-vector of X-ray beam parallel to c-axis, i.e., with the electric field of X-ray beam E//ab, using a 17-T magnetic field parallel to the c-axis of a Bi2212 single crystal. Numerical simulations of the XMCD signal of Bi2212 by multiple scattering theory have shown agreement with the experimental XMCD signal only for the local structure with noncentrosymmetric Bb2b space group of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+y}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Ab Initio Study of Structural, Electronic, and Magnetic Properties of A{sub 1−x}{sup III}Mn{sub x}B{sup VI}: In{sub 1−x}Mn{sub x}S-Diluted Magnetic Semiconductor

First-principles density functional calculations on the new class of diluted magnetic semiconductor A{sub 1−x}{sup III}Mn{sub x}B{sup VI} In{sub 1−x}Mn{sub x}S for x = 0.25 and 0.5 are investigated to study the structural, electronic, and magnetic properties, employing the full-potential linearized augmented plane wave method. Electronic band structures and density of states revealed a half-metallic character of In{sub 1−x}Mn{sub x}S and show the stability of anti-ferromagnetic states as compared with ferromagnetic states. The calculated exchange constants J{sub dd} are in good agreement with experimental and theoretical results on magnetic properties of single crystalline A{sub 1−x}{sup III}Mn{sub x}B{sup VI} in the anti-ferromagnetic case. Our predicated calculations on the s,p-d exchange constants N{sub 0}α and N{sub 0}β show that they are lower than in A{sub 1−x}{sup II}Mn{sub x}B{sup VI} DMS. The local environment is found tetrahedral as in the II–VI DMS and other (III,Mn) VI compounds. The total magnetic moment for In{sub 1−x}Mn{sub x}S for different concentrations is in accordance with the exact value 5 μ{sub B} and comes mainly from impurity Mn. The local magnetic moments of Mn ions are reduced from their free space charges values due to the p-d hybridization which produces small magnetic moments on the nonmagnetic In and S sites. The Curie temperature of In{sub 1−x}Mn{sub x}S is calculated within the mean field approximation and compared with other DMS systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Abnormal Transport and Magnetic Properties Induced by Change of the Phase Volume Ratio for YBa{sub 2}Cu{sub 3}O{sub 7-δ}/La{sub 0.67}Sr{sub 0.33}MnO{sub 3} Hybrids

Two elaborately designed hybrids consisting of superconducting YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) and ferromagnetic La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (LSMO), namely 20 × (YBCO(m)/LSMO(100 − m)) are prepared on single crystal SrTiO{sub 3} (STO) by pulsed laser deposition (PLD) with 20 being repetition periods and m = 90 and 10, respectively, which represents YBCO pulse number in a period. The films show highly c-oriented and epitaxial quality, suggested by XRD 𝜃–2𝜃 scans and pole figures. The 20 × (YBCO90/LSMO10) sample with a large YBCO volume fraction exhibits the typical character of a metal superconductor at about 90 K, while its transition width reaches 9.1 K, which is nearly eight times of that of the pure YBCO film. Above the superconducting transition temperature, a superparamagnetic signal rather than ferromagnetic behavior is observed, which may be associated with a diluted system consisting of the ferromagnetic nanoparticles embedded in the superconducting films. For the hybrid with a small YBCO volume fraction, i.e., the 20 × (YBCO10/LSMO90) sample, its transport behavior at normal state is insulating, and it is found that the Mott variable range hopping conduction dominates in this insulating phase in the temperature range 70–310 K. Obviously distinguishable insulator to superconductor (IS) transition occurs at 52 K, but the superconducting diamagnetic signals are very weak in the magnetic measurements below the IS temperature. For this sample, the magnetization loop at 100 K is ferromagnetic, yet manifested by a reduced coercive field and residual magnetization as compared with a pure LSMO film. In fact, both hybrids represent two kinds of nanocomposites, i.e., superconducting nanoparticles in a ferromagnetic matrix and ferromagnetic nanoparticles in a superconducting matrix, which benefits to study interfacial interactions due to an increased interface to value ratio and reduced size effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗