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Using density functional theory, the interface local magnetic moment and its variation are explored in SrRuO3|LaAlO3|vacuum (001) heterostructures with increasing number of LaAlO3 unit cells. The computed magnetic moment projected on interface planes is found to modulate nearly periodically as the number of LaAlO3 unit cells is increased in SrRuO3|LaAlO3|vacuum structure. The magnetic moment localized at the interface RuO2 plane shifts from a lower value of $\sim 0.7~\mu _{B}$ to a higher value of $\sim 1.35~\mu _{B}$ and changes by ~42% as LaAlO3 changes from non-stoichiometric to stoichiometric with increase in its thickness. However, the magnitude shifts from higher to lower value as LaAlO3 changes from stoichiometric to non-stoichiometric with further increase in thickness. The large variation and nearly periodic modulation of magnetic moment localized at the interface with increasing LaAlO3 thickness arise due to spin-dependent screening of effective total charge of LaAlO3 film by accumulated free carriers at the interface in heterostructure. The modulation of interface local magnetic moment using ultrathin LaAlO3 film at the oxide heterointerfaces can be exploited as an additional functionality, in conjunction with those reported recently such as control of band alignment and enhancement of the electric conductivity at the interface. [ABSTRACT FROM AUTHOR]

We have investigated the structure, magnetic, and electrical properties, and the resistance switching effect (RSE) of La2NiO $_{{ {4+\delta }}} compounds with different excess oxygen levels of \delta = 0.004 - 0.031 . Our results showed the structure changes from tetragonal I4/mmm to orthorhombic Fmmm when reducing \delta value from 0.011 to 0.006. The M(H) curves measured at several temperatures exhibit a coexistence of the weak ferromagnetic and antiferromagnetic interactions. Two shoulders on M(T) curves related to the spin and charge ordering have also been observed. These ordering temperatures depend strongly on \delta ) and low ( RL ) values. The resistance change ratio of the samples defined as 100% \times [RH - RL]/RL is found to be about 18%–57%, which depends on the value of $\delta $ in the samples. [ABSTRACT FROM AUTHOR]

Hydrogenated La(Fe,Mn,Si)13-based alloys have an excellent magnetocaloric properties, but poor mechanical and chemical stability. This hinders their direct machining and implementation in an active magnetic regenerator (AMR). In this paper, we show how machinability and corrosion protection of the particles can be improved by a hot-dip coating. To avoid the loss of hydrogen during the coating process, a low melting temperature eutectic Bi–Sn–In alloy was selected as a metal binder. The coated particles were used to build a packed bed regenerator as an array of fixed particles, avoiding such negative effects as sedimentation, segregation, and channel deformation. Similarity theory, combined with unsteady heat transfer approach was applied in order to calculate the optimal operation frequency and to estimate the maximal cooling power of the magnetocaloric regenerators. Two different geometries of heat exchangers were theoretically compared: stacked flat plate/channel structure and packed bed of equidimensional spherical particles. It is shown that, operating at low frequency, the same amount of magnetocaloric material can expel bigger amount of heat, when formed as packed bed heat exchangers. The metal-bonded packed bed regenerator made from La(Fe,Mn,Si)13Hx powder was tested in a home-build versatile testing device in a magnetic field change of 10 kOe. The maximal achievable temperature span as a function of both parameters—hot end temperature and length of regenerator—was explored. The largest thermal span of 8 K was produced by the regenerator with 40 mm length. [ABSTRACT FROM AUTHOR]

High- $k$ barium strontium titanate (BST) thin films were deposited onto glass substrates to demonstrate integrated capacitors for power supply in high-speed digital packages. Ferroelectric BST films were sputter deposited onto solution-derived lanthanum nickel oxide (LNO) electrodes. Zirconium oxide was studied for the first time as a barrier between glass and LNO electrodes to prevent electrode (LNO) interdiffusion into the glass substrate. The LNO and BST films were annealed in an oxygen-rich atmosphere at 650 °C. A capacitance density of 20–30 nF/mm2 was obtained at an operating voltage of 3 V. Leakage currents of 1–10 nA/nF were measured up to 3 V. These properties demonstrate the potential for low-cost high- $k$ thin-film decoupling capacitors in 2-D, 2.5-D, and 3-D glass interposers. A process to integrate and test such capacitors on glass substrates using sequential dielectric and electrode patterning is also demonstrated. [ABSTRACT FROM PUBLISHER]

Influences of La–Ce substitution on the microstructure and mechanical properties of R2Fe14B-type (R: rare earth) permanent magnets have been investigated. The results show that the optimum compressive and bending strengths of 1137.8 and 339.9 MPa, respectively, are achieved at 18 wt.% La–Ce substitution for Pr–Nd. La–Ce substitution is found to enhance the micro-hardness and Young’s modulus of 2:14:1 matrix phase gradually, strengthening the main phase grains. The irregular grain growth together with weakened R-rich intergranular phase in higher La/Ce-containing magnets, however, leads to easier crack propagation, hence deteriorating the mechanical properties. Consequently, R–Fe–B permanent magnet with a proper La–Ce content satisfies the constraints of cost, and magnetic and mechanical properties simultaneously, thereby exhibiting competitive advantages for mass production. [ABSTRACT FROM PUBLISHER]

LaBr_3:Ce crystal scintillator can be co-doped with various alkaline earth metals to improve light output and energy resolution of the basic scintillator. Another benefit is improvement of alpha/gamma discrimination via pulse shape analysis. LaBr_3:Ce contains a low level of actinium contamination, which produces an alpha particle background in radiation energy spectra. This background is difficult to discriminate from gamma rays. Conversely, the addition of co-dopant into the crystal makes the alpha response much easier to distinguish. LaBr_3:Ce, Sr, for example, produces a slow decay component in the scintillation pulse when excited by radiation. The amplitude of the slow decay component changes in response to a gamma ray versus a heavy charged particle. The change in pulse shape can be used to eliminate the alpha background or enable detection of neutron reaction products. [ABSTRACT FROM AUTHOR]

Tensile strain effects on the magnetic and electrical properties of La0.5Ca0.5MnO3 (LCMO5) films deposited on SrTiO3 (001) substrates are investigated with varying the thickness of LCMO5 from 16.5 to 62.2 nm. A microstructure analysis indicates that the film remains tensile-strain state with its thickness thinner than 50 nm. Magnetic measurements show that the ferromagnetic (FM) transition temperature ( TC ) of the films increases from 250 to 265 K with the film evolving from tensile to relaxed state. Meanwhile, the saturation magnetization at 5 K increases from 21.88 to 43.88 emu/cm3. It is interesting to find that colossal magnetoresistance is drastically enhanced from 18% to 740% with increasing the film thickness from 22.2 to 62.2 nm, which is attributed to the relaxation of tensile strain in association with an enhancement of FM interaction within an antiferromagnetic matrix. [ABSTRACT FROM AUTHOR]

The epitaxial thin films of electron-doped infinite-layer cuprate superconductor Sr1-xLaxCuO2 (SLCO; $x = 0.1$ ) were grown by dc magnetron sputtering, and their structural and electrical properties were systematically investigated by changing mismatch to substrate and SLCO film thickness, with a reduction annealing period under vacuum to remove the excess apex oxygen. Thin films of BaySr1−yTiO3 (BSTO) with y = 0.55$ , 0.6, and 0.7, prepared on (001) (La0.18Sr0.82)(Al0.59Ta0.41)O3 substrates, were used as the epitaxial buffer layers to induce different levels of tensile strain in c$ -axis-oriented SLCO, while (001) LaAlO3 substrates were used for the growth of a value of c$ -axis oriented SLCO was obtained on the BSTO ( y = 0.6$ ) layers and the mismatch dependence of strain relaxation thickness was clarified. The strain in a was obtained in the $a$ -axis SLCO for the first time. Based on these results, the strain effects of the SLCO film properties are discussed. [ABSTRACT FROM AUTHOR]

Composite materials containing hydrogenated La(Fe,Mn,Si)13 powder and 5 wt.% of polymer binder have very good magnetocaloric properties and can be machined in a heat exchanger. These heat exchangers have to fulfill certain requirements regarding their mechanical and chemical stability. In this paper, we have investigated the magnetocaloric properties of thin composite plates produced by two different methods: 1) wire saw cutting and 2) cold rolling. The flexural strength of the plates was investigated by three-point bending method. Furthermore, the corrosive behavior of the plates in different heat transfer fluids was investigated. Finally, the adiabatic temperature change and the magnetic entropy change of the plates were observed over a seven-month period in order to evaluate their applicability in a real device. [ABSTRACT FROM AUTHOR]

The compressive and tensile strains induced by different substrates on La0.325Pr0.3Ca0.375MnO3 (LPCMO) thin films have been investigated. It is found that the in-plane compressive strain favors the ferromagnetic metallic phase by increasing the hopping amplitude between neighboring elections and decreasing the tilt of the MnO6 octahedron, leading to the weakening of the phase separation. On the other hand, the in-plane tensile strain in films prefers to increase the stability of long-range charge/orbital ordering (COO) phase. Under 5 T magnetic field, the 30 nm LPCMO films on NGO and LSAT substrates show an obvious metal–insulator transition, indicating that the COO phase can be melted by the magnetic field at low temperature in the film with small in-plane tensile strain. The LPCMO film on STO substrate keeps insulating in the entire measuring temperature range even under 5 T magnetic field, suggesting that the COO phase in the film with a large tensile strain is more robust. [ABSTRACT FROM AUTHOR]

Though enzyme-linked immunosorbent assay is widely used in laboratory medicine, it has limitations due to interactions between enzymes and secondary antibodies. Here, we propose a new cardiac assay scheme for detecting troponin I antigens based on La(1–x)SrxMnO3 ( $x=0.10$ , 0.15, and 0.25) nanoparticles (NPs). These NPs are synthesized via a modified polyol process followed by heat treatment. An increase in $x$ induces changes in crystal structure and increases both Curie temperature and saturation magnetization. The NPs with $x=0.15$ exhibit a Curie temperature close to the human body temperature. The limit of detection is found to be 0.78 ng/mL. We also confirm that LaSrMnO NPs are reusable after heating the assay plate. [ABSTRACT FROM AUTHOR]

Temperature-dependent electron spin resonance (ESR) is applied to investigate La0.9Sr0.1MnO3 nanoparticles incorporating with magnetization and electrical transport measurements. Ferromagnetism is observed at room temperature which is much higher than the TC value for bulk samples ( $\sim $ 150 K). The ESR analysis confirms the coexistence of multiple magnetic phases consistent with the field-dependent magnetization-temperature curves. By fitting ESR spectra, the room-temperature multiphases are identified as the mixture of ferromagnetic and paramagnetic states, similar to the Griffiths phase observed in bulk samples. The field-dependent resistivity shows colossal magnetoresistance effect up to room temperature. Based on our analysis, the size-effect-induced room-temperature ferromagnetism is strongly correlated with the enhancement of the Griffith phase separation temperature. [ABSTRACT FROM AUTHOR]

In this paper, we present a detailed study on the magnetocaloric effect (MCE) and the critical behavior of La2NiMnO6 (LNMO) nanocrystals. Cubic-structured LNMO samples with different crystallite sizes (d = 200 to 26.4 nm) were prepared by a combination of solid-state reaction and mechanical milling with milling time ({t_{m}}) changing from 0 to 30 min. The results show that all the samples undergo the second-order phase transition. Using the modified Arrott plot and critical isotherm analysis methods, we have analyzed the critical behavior for nanocrystals to obtain the optimal values of the critical parameters ( \beta, \gamma, \delta , and TC ). The results indicate that short- and long-range ferromagnetic interactions coexist in the samples. In addition, we also assess the MCE of the samples via the magnetic entropy change ( {\Delta {SM}} ). Based on the obtained \Delta Sm (T, H) data, we have also described the universal master curve for \Delta SM which as a function of \Delta SM (T)/ \Delta {SM^{P}} versus rescaled temperature \theta = (T - TC)/({Tr - TC)} where Tr is the reference temperature. Interestingly, all the \Delta SM (T, H)^{H} data points are collapsed into a universal curve in the whole temperature range. [ABSTRACT FROM AUTHOR]

The critical phenomena around the Curie temperature ( TC ) of a polycrystalline La0.7Sr0.3Mn0.9Ti0.1O3 were studied based on magnetic field and temperature dependence of magnetization. Using the modified Arrott plot method, we determined the critical parameters TC \approx 234 K, \beta =0.372 \pm 0.012 , \gamma =1.171 \pm 0.112 , and \delta = 4.15 \pm 0.01 . With these critical values, the M(H) data of the sample fall onto two universal branches of the scaling function , where \varepsilon = (T-T_{C})/T_{C} , and f_{+} for T > TC and f- for T < TC . This pointed to the existence of a short-range ferromagnetic (FM) order in La0.7Sr0.3Mn0.9Ti0.1O3, which is attributed to FM clusters persisting in a wide temperature range, even above T_C . Electron-spin-resonance spectra affirmed the presence of the FM clusters at temperatures as high as T = T\mathrm {min}(\approx 1.3 ~TC) , above which the sample is completely paramagnetic. Based on the M(H) data, we also calculated the magnetic-entropy change ( \Delta Sm) , which reached a maximum ( \vert \Delta S\mathrm {max}\vert ) \approx 4.3 J/kg \cdot K) around the {\rm T}_{C} , corresponding to the relative cooling power of \sim 200 J/kg for a field change \Delta H = 50 ~\textrm kOe . A linear relationship \vert \Delta S\mathrm {max}\vert \propto H^{n} is achieved with a local exponent $n = 0.59$ determined from $n = 1+ (\beta - 1)/(\beta + \gamma)$ , indicative of a short-range FM system. [ABSTRACT FROM AUTHOR]

Here, we report strain-induced high coercivity in La0.7Sr0.3CoO3 (LSCO) films, which suffer in-plane tensile strains due to the positive lattice mismatch between the substrate and the LSCO bulk. The films on (011)-0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 exhibit large uniaxial anisotropy, large coercivity, and high saturation magnetization at low temperature in contrast to the well soft magnetic behaviors in LSCO bulk. It is found that the coercivity of the 40 nm (001)-LSCO/SrTiO3 film can be as high as 1.45 T at 10 K and the observed coercivity decreases rapidly as the thickness increases, though the Curie temperature is below room temperature. The large coercivity and anisotropy should be closely related to the strain-induced structural changes and the different orbital ordering of Co3+ and Co4+ ions. Meanwhile, the enhanced domain wall pinning by the tensile strain may also contribute to the observed high coercivity. [ABSTRACT FROM AUTHOR]

The magnetic La1-xSrxMnO3 particles of \approx 50 nm size have been prepared in the flux of sodium nitrite at \approx 500^{\circ }\text{C} . A detailed magnetic study, including the neutron diffraction at zero and high pressures, has been performed on compositions x = 0.28$ and 0.37, as well as on comparative samples prepared via sol–gel route. Based on these experiments, we conclude that the molten salt prepared particles show significant oxygen excess $\delta $ > 0 that can be ascribed mainly to the surface oxygen chemisorption. As a consequence, the valence of Mn ions is shifted toward a higher oxidation state, and this shift probably exhibits a pronounced radial distribution in the particles, reaching possibly pure Mn4+ at the uppermost surface layer. We suggest that such overdoping is an additional reason for magnetically dead shell in manganite nanoparticles and is also the source of surface stress that compresses the particle core and modifies its physical properties. Such compressive stress drives the magnetic ground state of the composition $x = 0.37$ toward a mixture of ferromagnetic (FM) and A-type anti-FM (AFM) ordering. Although the surface effects should also occur in the particles with $x = 0.28$ , the AFM phase is practically absent in this sample but can be induced by high pressure. [ABSTRACT FROM AUTHOR]

We report magnetic interactions and electronic transport properties in La0.4Bi0.6Mn0.5Ti0.5O3 perovskite manganite synthesized using solid-state route. After characterizing the samples structurally, the systematic investigations of magnetic and electrical transport behaviors have been undertaken. It has been observed that at low temperatures near TC, the sample is magnetically frustrated leading to the second-order magnetic transition. A justification for the observed magnetic behavior has been explained based on Arrott’s plot study. The resistivity as a function of temperature in the absence and the presence of applied magnetic field suggests semiconducting nature of the sample. The conduction of the charge carriers is explained using Shklovskii-Efros-type variable-range-hopping mechanism. [ABSTRACT FROM AUTHOR]

This work describes the development of a gamma detector based on silicon drift detectors (SDDs) to read out large \LaBr_3:\Ce scintillators for gamma-ray astronomy applications, within an activity supported by the European Space Agency (ESA). SDDs, characterized by high quantum efficiency and low electronic noise, when coupled with a scintillator are good candidates for gamma-ray spectroscopy applications in a wide energy range, e.g., from 150 keV to 15 MeV. The gamma-ray detector prototype presented here is composed of a 2^\prime^\prime\times2^\prime^\prime \LaBr_3:\Ce scintillator coupled with four SDD arrays arranged in a 2 \times 2 format (a total of 36 SDDs). This detection system is operated with custom readout application specific integrated circuits (ASICs) and a data acquisition (DAQ) system. With this prototype gamma-camera, an energy resolution of 3.4% FWHM at 662 keV has been measured. Spectroscopy measurements have been carried out between 300 keV and 1800 keV and the achieved results are consistent with the electronic noise of the SDD technology. In this work, we report on the SDD based detection head’s design, its X-ray characterization, readout electronics, experimental setups and gamma-ray spectroscopy results. Finally, perspectives with the possible use of an improved SDD technology are discussed. [ABSTRACT FROM AUTHOR]

The gas-sensing properties of orthorhombic and spinel ferrites (LaFeO3, NiFe2O4 and CoFe2O4) prepared by self-propagating high-temperature synthesis (SHS) have been investigated. This is one of the first reports of using an SHS derived powder for gas sensing applications. The gas response of the materials was tested against a wide range of environmentally important gases (ethanol, ethane, ethene, ammonia, propane, and CO) at a range of different operating temperatures. Good gas response behavior was found with excellent selectivity toward ethanol, particularly in the case of the LaFeO3 sensor. [ABSTRACT FROM PUBLISHER]

An Er3+-doped ZBLAN fiber amplifier for Q-switched pulses at 2.79 μm is reported. Over 24 μJ of pulse energy at an average output power of 1.0 W was achieved at a maximum available pump power of 9.4 W. The efficiency of this pulsed laser fiber amplifier is about 10%. Our simulation predicts that over 300-μJ pulses can be achieved with this fiber amplifier when a 120-W pump is used. [ABSTRACT FROM PUBLISHER]

We report a high power single-end output amplified spontaneous emission (ASE) Ho-doped ZBLAN fiber source near 3 μm. Different from the conventional ASE transitions terminating on ground state where spectra narrowing or essentially unchanging was exhibited at increased pump power, the ASE transition occurred between metastable levels in this case showed distinguished spectrum evolution with increasing pump power, i.e., broadening first then narrowing. In addition, compared with copropagating pumped scheme, better performance was shown under counter-propagating pumped scheme where the broadest spectrum coverage of ~130 nm spanning from ~2845 to ~2975 nm with an full-width at half-maximum (FWHM) bandwidth of ~46 nm and an output power of 43.65 mW was achieved. As further pump power increasing, the reported highest ASE power of 219.76 mW at 3-μm waveband was also achieved at a slope efficiency of 11.11% with a narrowed FWHM bandwidth of ~26 nm and a red-shifted peak wavelength of 2925 nm. [ABSTRACT FROM PUBLISHER]

The magnetic and structural properties of bulk, ball-milled La(Co5-xFex), and ball-milled La2(Co7-xFex) were studied. The highest coercivity (1.08 T) was obtained at room temperature for ball-milled LaCo4.8Fe0.2 after annealing in a preheated furnace at 800 °C for 3 min and subsequently quenching. Iron doping up to $x = 1$ increased the saturation magnetization by up to 20% without any deterioration of coercivity. For La2(Co7-xFex), the highest coercivity (1.2 T) at room temperature and (1.92 T) at 4 K was obtained for ball-milled La2Co7 after annealing in the preheated furnace at 850 °C for 3 min and subsequently quenching. Unlike Fe-doped LaCo5, iron doping in La2Co7 did not enhance the saturation magnetization. [ABSTRACT FROM AUTHOR]

Electrical resistance R , heat capacity C , ac susceptibility, and magnetic moment of orthorhombic La0.85Ag0.15MnO3 ceramic were investigated in magnetic fields with flux density up to 5 T and in high hydrostatic pressures up to 0.9 GPa. Sharp lambda-like anomalies in R(T) and C(T) indicate ferromagnetic (FM)–paramagnetic transition. Magnetic field shifts these anomalies to higher temperature and smears them out confirming FM origin of the ordering. Magneto-resistance is negative and large reaching maximal value of about 70% for field with flux density of 5 T at the magnetic phase transition. The magnetic phase transition is accompanied with anomalies at 219.5 K in \chi '(T) and at 221 K in increases with applied pressure with the rate dT_{C}/dp=14.2 K/GPa. Magnetocaloric effect was evaluated from the magnetic entropy change \Delta S , which was determined independently from heat capacity and magnetic moment measurements. The maximal values were obtained for \mu 0 \Delta H=5 T and both values -\Delta S=5.85 Jkg ^-1 K ^-1 (heat capacity) and $-\Delta S=5.80$ Jkg ^-1 K ^-1 (magnetic moment) are comparable. Hydrostatic pressure of 0.84 GPa leads to an enhancement of $-\Delta S$ approximately about 14%. [ABSTRACT FROM AUTHOR]

High-frequency (HF) magnetic properties have been studied for manganites La1-xSrxMnO3 with Sr = 0.2-0.4. The manganites have good HF properties with the real permeability μ0' of 50-80, maximum imaginary permeability μmax" of 22-32, and resonance frequency of 10-40 MHz. Two types of resonances are found for La1-xSrxMnO3: one is from domain wall and the other is from natural resonance. With increasing annealing temperature Ta, μ0' significantly increases, which is attributed to an increase of density, based on the magnetic circuit model. The frequency fR2 of natural resonance is almost unchanged, but fR1 of wall resonance is shifted to lower frequency that has its origin in the decrease of resistivity. [ABSTRACT FROM PUBLISHER]

The influence of a thick epitaxial buffer layer on the magnetic properties of thin perovskite manganite films was studied. The deposition of a thick LaNiO3 buffer on single-crystal (001) LaAlO3 substrate shifted the magnetic anisotropy of a thin La0.7Sr0.3MnO3 toward the sample plane, while maintaining its saturation magnetization. Possible origins for such an effect are discussed. This paper highlights the sensitivity of magnetic properties in manganites on the presence of buffer layers. [ABSTRACT FROM PUBLISHER]

La1.5Sr0.5NiO4 is well known as a dielectric material that has a colossal permittivity (up to 10^7 ) and a weak paramagnet at room temperature. The permeability is about 1.005, which is just slightly larger than that of air. The weak magnetic moment together with the huge imbalance between permittivity and permeability seemed to negate La1.5Sr0.5NiO4 as a promising candidate for electromagnetic absorption due to the lack of magnetic losses. However, we have found that La1.5Sr0.5NiO4 nanopowder indeed has a reasonably strong microwave absorption capability in the range of 4–18 GHz. Apparently, impedance matching (\vert Z\vert=Z0=377~\Omega) is found to be responsible for the absorption resonance that shifts to lower frequencies with increasing the absorber's thickness. To improve magnetic losses, as well as to balance out the dielectric and magnetic components, CoFe2O4 nanoparticles are gradually added to the La1.5Sr0.5NiO4/CoFe2O4 composites. The influence of adding magnetic nanoparticles on reflection loss, resonance frequency, and matching effects will be discussed. [ABSTRACT FROM AUTHOR]

Bilayered perovskite manganites of the composition La1.25Sr1.75Mn2O7 (LSMO) were synthesized successfully by the sol–gel method. The effects of pH concentration, calcination temperature, and time on the phase formation, structure, and magnetic properties of the material were systematically investigated. X-ray diffraction and Rietveld refinement analysis revealed that the single phase of LSMO was only obtained in samples sintered at a temperature as high as 1250 °C. The best magnetic properties were achieved in samples with \({\rm pH} = 7\) , calcinated at 1450 °C for 10 h. Our studies show that the pH concentration, calcination temperature, and time are important factors in tailoring the magnetic properties of double-layered perovskite manganites. [ABSTRACT FROM AUTHOR]

Perovskite nanoparticles La1-xSrxMnO3 were successfully synthesized by modified sol-gel method. Their structure and magnetic properties were systematically investigated in dependence on doped Sr ratio $x$ . The structure was investigated by X-ray diffraction and showed a slight change, but magnetic properties varied strongly with changing $x$ . Magnetic properties of samples studied by physical property measurement system show spin-glass behavior with Curie temperature and blocking temperatures above room temperature. The blocking temperature as well as Curie temperature varies by changing $x$ . At room temperature, the samples show superparamagnetic properties with high saturation magnetization $M_{{S}}$ up to 87 emu/g, which strongly depends on the doped Sr ratio $x$ . [ABSTRACT FROM AUTHOR]

We improved our glue splicing method to join silica and fluoride glass fibers. It is now even more robust and stabile with a mean loss below 0.5 dB. Moreover, the splice reflection was reduced to about -42 dB when an index matching gel was used. Pieces of Pr3+/Yb3+ doped ZBLAN fibers with lengths of 25 cm were connected to silica fibers. In a fiber laser resonator 6 mW of red laser radiation was achieved with the spliced fibers at a pump power level of 144 mW at 845 nm. [ABSTRACT FROM PUBLISHER]

Experimental studies of LaBr3 doped with 5%, 10%, 20% and 30% Ce^3+ and CeBr3 are performed for application in TOF-PET. X-ray excited emission spectra, decay time constants, photoelectron yields and energy resolutions are measured from 100 K to 600 K. The results show a strong temperature and Ce^3+ concentration dependence, which is mostly explained by Ce^3+ self-absorption. We modeled how self-absorption affects the scintillation pulse shape and what the consequences are for the detector timing resolution. It shows that self-absorption elongates the decay time constant, whilst it does not affect the scintillation rise time. [ABSTRACT FROM PUBLISHER]

The magnetic exchange coupling effect has been investigated in \La0.7{\Sr}0.3{\MnO}3 (LSMO)-NiO nanocomposite films prepared by pulsed laser deposition on \SrTiO3 (001) and (110) single crystal substrates. The films show an enhanced coercivity field HC= 560 ~\Oe compared with the same thickness single pure LSMO thin film. The composite films exhibit a large exchange bias field HE = 140 ~\Oe after applying a 4000 Oe field cooling. The values of the exchange bias field decrease with increasing temperature and become zero at about 45 K, which corresponds to the conventional exchange bias blocking temperature (TB), regardless of epitaxial growth directions on (001) or (110) \SrTiO3 substrates. We speculate that there may be magnetic interaction at the NiO and LSMO boundaries or charge transfer between the Ni and Mn ions, resulting in the formation of ferromagnetic interaction at the interface. The Curie temperature TC decreased from 340 K of the LSMO single film to 200 K of the nanocomposite film. The results demonstrate that the magnetic state of the composite film is directly related to the Mn-O-Mn and Mn-O-Ni spin interaction energy. In addition to this, the Mn-O-Ni at the boundary may also form the magnetic region that pins the ferromagnetic LSMO phase. [ABSTRACT FROM PUBLISHER]

Metal oxides show fascinating physical properties such as ferromagnetism, antiferromagnetism, high temperature superconductivity, ferroelectricity, or even multiferroicity. For many possible electronic applications as well as fundamental studies, it is essential to fabricate epitaxial layered films and multilayers of these materials having complex lattice structures with sharp interfaces, preserving epitaxiallity through the whole structure. We have grown these kind of oxide heterostructures on single crystal (001) oriented SrTiO3 substrates by using an in-situ DC sputtering technique at high oxygen pressures. Specifically, we report the study of magnetic and transport properties in ferromagnetic/antiferromagnetic, F/AF, heterostructures based on the Ca-doped lanthanum manganite system. We artificially grew La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 heterostructures, maintaining constant the total thickness of the sample and systematically varying the thicknesses of the antiferromagnetic layer (tAF) and ferromagnetic layer (tF). Magnetization measurements indicate a dependence of Curie temperature, exchange bias field, and magnetoresistance behavior with the tAF/tF ratio. [ABSTRACT FROM PUBLISHER]

Ferromagnetic thin films of La2/3Ca1/3MnO3 manganite were grown by pulsed laser deposition, under different oxygen atmospheres, on silicon substrates. We performed structural, magnetic, spectroscopic, and electrical characterization of the films. Resistive switching between high and low resistance states was obtained upon pulsing with opposite polarities voltages. The I-V curves exhibit sharp transitions between these states. The RS properties are strongly dependant on the films oxygen stochiometry and on the compliance current used for producing the high to low transition. ON/OFF ratios as high as 1000 were obtained for optimal RS conditions. Obtained results are discussed within the framework of mobile oxygen vacancies. [ABSTRACT FROM PUBLISHER]

Presently, a majority of studies concerning application of silicon photomultipliers (SiPMs) in positron emission tomography detectors are focused on scintillators containing lanthanum (\LaBr3) or lutetium (LSO, LYSO, or LFS). However, the modules with the well-known BGO in combination with SiPM light readout are also interesting, owing unique features of SiPMs. In this paper, the two types of detectors, based on BGO and LSO scintillators, are compared in terms of requirements for positron emission tomography scanners. The presented studies are performed with two Hamamatsu Multi Pixel Photon Counter (MPPC) arrays of 2 \times 2 channels, with the total area of 6\times 6\ \mm^2 and micro-pixel size of 25 \mu\m (S10985-025C) and 50 \mu\m (S10985-050C). The measurements of a number of photoelectrons, energy resolution at 511 keV and ^22\Na time resolution are reported for various sizes of the scintillators, including 2.75\times 2.75\times 20\ \mm^3 pixel and single crystals covering the whole MPPC active area. The paper is more focused on optimization of the system with BGO as its performance in combination with SiPM light readout is less known. The aim of this work is to show advantages of a SiPM-based detector, especially in combination with BGO, in respect to the block detectors where classic photomultipliers are used. [ABSTRACT FROM PUBLISHER]

Clinical TOF PET systems achieve detection efficiency using thick crystals, typically of thickness 2–3 cm. The resulting dispersion in interaction depths degrades spatial resolution for increasing radial positions due to parallax error. Furthermore, interaction depth dispersion results in time pickoff dispersion and thus in degraded timing resolution, and is therefore of added concern in TOF scanners. Using fast signal digitization, we characterize the timing performance, pulse shape and light output of LaBr3{:}Ce, CeBr3 and LYSO. Coincidence timing resolution is shown to degrade by \sim 50~ps/cm for scintillator pixels of constant cross section and increasing length. By controlling irradiation depth in a scintillator pixel, we show that DOI-dependence of time pickoff is a significant factor in the loss of timing performance in thick detectors. Using the correlated DOI-dependence of time pickoff and charge collection, we apply a charge-based correction to the time pickoff, obtaining improved coincidence timing resolution of < 200~ps for a uniform 4\,\times\,4\,\times\,30 mm^3~LaBr_3 pixel. In order to obtain both DOI identification and improved timing resolution, we design a two layer LaBr3[5\%Ce]/LaBr3[30\%Ce] detector of total size 4\,\times\,4\,\times\,30 mm^3, exploiting the dependence of scintillator rise time on [Ce] in LaBr3{:}Ce. Using signal rise time to determine interaction layer, excellent interaction layer discrimination is achieved, while maintaining coincidence timing resolution of < 250~ps and energy resolution <7\% using a R4998 PMT. Excellent layer separation and timing performance is measured with several other commercially-available TOF photodetectors, demonstrating the practicality of this design. These results indicate the feasibility of rise time discrimination as a technique for measuring event DOI while maintaining sensitivity, timing and energy performance, in a well-known detector architecture. [ABSTRACT FROM PUBLISHER]

We have studied the antiferromagnetic coupling at the interface of the La0.7Sr0.3MnO3/SrRuO3 bilayer as function of temperature. We measured the La0.7Sr0.3MnO3 magnetization reversal while the SrRuO3 magnetization is blocked due to a field cooled procedure and because of its high coercive field. Even if in this system, the La0.7Sr0.3MnO3 magnetization cycle may be explained by two exchange couplings which coexist up to 120 K, the exchange bias and the coercive field from 5 K to 300 K have a similar behavior from some ferromagnetic/antiferromagnetic systems. [ABSTRACT FROM AUTHOR]

We have studied magnetic and magnetotransport properties of a polycrystalline ceramics of La0.7Sr0.2Ca0.1MnO3 (LSCM) prepared from nanoparticles. The Curie temperature (TC) of the sample is about 340 K. Basing on the magnetic-field dependences of magnetization measured around TC, maximum magnetic-entropy changes under the applied fields of 10, 20 and 30 kOe are about 1.73, 2.74, 3.52 J/kg.K, respectively, which are higher than those reported on a parent compound of La0.7Sr0.3MnO3. To understand magnetic-interaction mechanisms taking place in the system, the critical behavior has been taken into account. By using the modified Arrott plot method, \beta and \gamma values associated with the spontaneous magnetization (Ms) and inverse initial susceptibility (\chi0^{-1}) have been obtained to be 0.472 \pm 0.016 and 1.061 \pm 0.024, respectively. These critical parameters are close to those expected for the mean-field theory (with \beta=0.5, and \gamma=1.0). A small deviation in value between our results and those expected for the mean-field theory could be due to an inhomogeneity in magnetism and/or interaction competitions between antiferromagnetic pairs (Mn^3+-Mn^3+ and Mn^4+-Mn^4+) and a ferromagnetic pair of Mn^3+-Mn^4+ in LSCM. Interestingly, in the temperature range of 180–300 K, magnetoresistance values keep quite stable at about 16 and 27% for the magnetic fields of 1 and 7 kOe, respectively. This makes LSCM more suitable to applications of magnetic sensitive sensors and reading heads working in a large temperature range. [ABSTRACT FROM PUBLISHER]

Space missions continue to demand higher power Hall thrusters that provide high thrust and long life. For in-space propulsion applications such as high-power orbit raising and cargo missions, Hall thrusters capable of operating in the range of 10-50 kW are in development. The hollow cathodes for these thrusters will be required to produce discharge currents of 20-100 A with lifetimes well in excess of 10 kh. A lanthanum hexaboride (LaB6) hollow cathode with these capabilities has been developed that features graphite tubes or sleeves to provide a diffusion boundary that protects the LaB6 electron emitter from chemical reactions with the refractory metal support structure and includes a long-life heater capable of igniting the high-temperature electron emitter. Cathode operation has been fully characterized at currents of 20-100 A including probe measurements of the plasma parameters inside the LaB6 insert and energetic ion measurements in the cathode plume. The cathode was also tested at up to 200 A of discharge current to explore the cathode failure mechanisms. While the LaB6 cathode operates at higher temperatures than conventional barium oxide-impregnated dispenser cathode, LaB6 provides very high discharge currents, long life, and significantly less sensitivity to propellant impurities and air exposure than conventional dispenser cathodes. [ABSTRACT FROM AUTHOR]

A shutter-based free-space optical switching architecture capable of multicast transmission functionality has been proposed as a promising switching technology for storage area network applications. The main idea behind this type of switching architecture is that the system performance can be enhanced with a new electro-optical material, used for the shutters to increase switching speed. It can be distinguished from previous shutter-based optical switches which have been based on single channel to single channel switching, as we present a reconfigurable design of a 6 × 6 72-channel shutter-based optical switching core based on multimode fiber ribbon to multimode fiber ribbon switching. The design and implementation of a prototype 6 × 6 72-channel multi-mode fiber ribbon switch demonstrator utilizing a submicrosecond PLZT-based spatial light modulator as a shutter is reported. The light loss, crosstalk, and data switching characteristics of the implemented fiber ribbon switch from the evaluation tests were measured and are presented. [ABSTRACT FROM PUBLISHER]

We conducted a theoretical and experimental study of the single-layer microwave absorbers employing ferrite composites. By combining zero-reflection solutions with the typical electromagnetic behavior of ferrites, we distinguish between matching mechanisms (resonance and geometrical type) which occur in bulk and composite specimens. Explicit design guidelines concerning the material properties are thereby indicated, contrary to empirical and erroneous design objectives. Additionally, the calculation of the thickness to \lambda/4 ratio is promoted to mitigate the common misconceptions about the reflection loss (RL) source. The simulated RL maps of new planar hexaferrite composites support our theoretical analysis. Furthermore, low rate La and Ni doping in SrCo2-W appears to yield increased RL (up to 45 and 65 dB) of wider bandwidth at lower frequency (6–18 GHz) and for smaller coating thicknesses. [ABSTRACT FROM PUBLISHER]

A charge-trap-type Flash memory with a \La2\O3-doped \Si3\N4 charge-trapping layer is demonstrated for the first time. An ultrathin \La2 \O3 layer is inserted in the middle of a \Si3 \N4 layer, followed by high-temperature annealing to mix the two layers. The \La2\O3-doped \Si3\N4 layer, irrespective of \Si3\N4 deposition processes, is found to provide deep charge-trapping sites, resulting in an excellent pre-/postcycling retention property and high reliability. The optimization of the \La2\O3 layer thickness and position in the \Si3\N4 trapping layer has been also systematically studied. [ABSTRACT FROM AUTHOR]

Magnetic properties and magnetocaloric effect were investigated on La0.5 + xPr0.5Fe11.4Si1.6Hy (x=0, 0.1, 0.2) melt-spun ribbons. It was found that NaZn13-type phase could be obtained easily owing to that the segregation of \alpha-Fe phase was suppressed obviously by adding appropriate amount of La after a short time annealing for melt-spun ribbons. For the La0.6Pr0.5Fe11.4Si1.6Hy ribbons, the Curie temperature was adjusted dramatically from low temperature of 193 K to room temperature of 321 K due to the interstitial hydrogen adsorption. With La content increasing, Curie temperature was slightly increased; the magnetic hysteresis was reduced, while a large magnetic entropy change remained. The maximum magnetic entropy change (- \Delta SM) is 33.8 J/(kg\cdotK) for La0.6Pr0.5Fe11.4Si1.6 while that of La0.6Pr0.5Fe11.4Si1.6Hy is 19.6 J/(kg\cdotK) in a magnetic field change of 5 T. It is shown that rapid quenching to make LaFe13 - xSix alloys is more cost effective than arc melting method by reducing annealing time substantially. High magnetic entropy change and low magnetic hysteresis were obtained by adding extra La and the Curie temperature was tuned to near room temperature by interstitial atom H. This work indicated that La0.6Pr0.5Fe11.4Si1.6Hy was a promising magnetic refrigeration material near room temperature. [ABSTRACT FROM AUTHOR]

Long-term aging treatments of partially hydrogenated ternary La–Fe–Si alloys show that these materials do not have stable magnetic properties. If partially hydrogenated LaFe13- xSixHz is held at its Curie temperature for several days it decomposes into a fraction with an increased Curie temperature and another one with decreased Curie temperature compared to the starting material. Such degrading material cannot be used in applications which require constant properties over a long period of time. By fully hydrogenating manganese containing LaFe13 - x - yMnySixHz, stable alloys with adjustable Curie temperatures around room temperature can be produced. These hydrides do not change their magnetic properties if they are operated close to their Curie temperature. [ABSTRACT FROM AUTHOR]

The magnetic properties of SmBa2{\Cu}3{\O}7-x (SmBCO) coated conductor (CC) that was fabricated on LaMnO3({\LMO})/{\IBAD-MgO} substrates using Evaporation using Drum in Dual Chamber (EDDC), which is a batch type co-evaporation system, was investigated. LMO buffer layer was deposited on IBAD-MgO templates by PLD method. The measurements of both the magnetization M(H) and the resistance R(T) for the SmBCO CC, were carried out at temperatures between 10 and 120 K in fields up to 8.5 T, using a PPMS-9T (with both ACMS and DCR options, Quantum Design). The SmBCO CC exhibited Tc (onset temperature) of 94.7 K with a narrow transition width of 0.6 K, which indicates a good homogeneity of the superconducting properties. The upper critical field Hc2 near Tc of the SmBCO CC has been estimated by the resistance R(T) approaches. The magnetization curves M(H) are symmetric about the line M=0 for the SmBCO CC with the field applied parallel to both the c-axis and c-axis +45^\circ. For the SmBCO CC with the field applied parallel to the ab-plane, they are asymmetric. These symmetric and asymmetric curves can be explained by introducing the bulk pinning of 1-D flux lines and surface barrier-dominated system of 2-D pancake vortices. [ABSTRACT FROM AUTHOR]

This paper focused on the modification properties of the La2Zr2O7 (LZO) seed layers for the epitaxial growth of thick LZO buffer films on cube-textured Ni5%W (Ni5W) substrate by the metal organic deposition (MOD) method. The surface morphologies of the LZO seed layers with different precursor concentrations were described by SEM. The grain orientation and the crystallographic growth model of the LZO seed layer were characterized by the electron backscatter diffraction (EBSD). The XRD analyses reveal that the LZO buffer layers on the Ni5W substrates with and without seed layers were grown epitaxially. However, the uniformly distributed islanded LZO seed layers with highly (001)[110] rotated cube texture not only can improve the crystallinity of the subsequent LZO buffer films, but also can optimize the in-plan and out-plan orientations of the thick LZO buffer layers. [ABSTRACT FROM AUTHOR]

In the present work, composite LaMnO3:MgO (LMO:MgO) cap buffer layers with varying MgO contents 5 vol% up to 75 vol% have been grown on homo-epi MgO/IBAD(MgO) substrates to enhance the performance of YBa2Cu3O7-x (YBCO) films. Results showed formation of phase separated MgO nanocolumns within the LMO matrix. The impact of these nanocolumns on the superconducting properties of YBCO films deposited using pulsed laser deposition (PLD) on the nanostructured layer was investigated by electrical transport measurements. Such YBCO films showed better in-field performance compared to that of YBCO films on standard LMO cap films. In particular, measurements of the field-angle dependence revealed c-axis correlated pinning for YBCO films on these composite cap layers. The present results demonstrate a practical approach to obtain high performance superconducting wires. [ABSTRACT FROM AUTHOR]

We report a new methodology for synthesizing oxypnictide superconductors with the commonly available potassium fluoride (KF) as a source of fluorine instead of expensive LaF3. This results in simultaneous doping of potassium at lanthanum sites and leads to a three-fold increase in the upper critical field. We report the Tc (onset) of 28.50 K by F-doping and highest upper critical field (\sim122 T) at ambient pressure in the family of La–based oxypnictides. To study the contribution from inter and intra-granular current density, we compare remanent magnetization measurements on La1.03{\O}0.9{\F}0.2{\FeAs} and La0.8{\K}0.2{\O}0.8{\F}0.2{\FeAs} superconductors that show only one major peak indicating substantial electromagnetic granularity. The Seebeck effect (S) with respect to temperature has negative sign and exhibits unconventional temperature dependence. Analysis of resistivity transition broadening under magnetic field reveals the signatures of Arrhenius behavior and the calculated activation energy follows power-law dependence with respect to magnetic field. [ABSTRACT FROM AUTHOR]

La3Ga5.5Ta0.5O14 (LGT) is a new piezoelectric material with superior electromechanical properties and high Q·f product. Transverse-wave splitting behavior of LGT was observed in the acoustic velocity measurements. The velocities of the two shear waves propagating in Y-(010) direction are very close and they cannot be separated completely. This has a tremendous influence on determining the correct velocity of the shear modes. It is proposed that the singular value decomposition (SVD) technique can be used to determine the splitting time of two shear modes in Y-plane LGT crystal. Moreover, it also helps to correct the arrival time of the transverse waves. It is believed that the presented approach is efficient and accurate for determining the correct velocities of shear modes in anisotropic media. [ABSTRACT FROM AUTHOR]

LaA1O3 is a promising candidate for gate dielectric of future VLSI devices. In this letter, n-channel metal-oxide-semiconductor field-effect transistors with LaA1O3 gate dielectric were fabricated, and the electron mobility degra- dation mechanisms were studied. The leakage current density is 7.6 x 10-5 A/cm² at -1 V. The dielectric constant is 17.5. The surface-recombination velocity, the minority-carrier lifetime, and the effective capture cross section of surface states were extracted from gated-diode measurement. The rate of threshold voltage change with temperature (ΔVT/ΔT) from 11 K to 400 K is -1.51 mV/K, and the electron mobility limited by surface roughness is proportional to Eeff-0.66. [ABSTRACT FROM AUTHOR]

Bulk samples of La(Fe, Co, Si)[sub13] have been prepared by powder metallurgy starting from elemental powders and cast master alloys. After sintering at about 1400 K for a few hours, the samples achieve densities of about 7.2 g/cm[sup3]. For ternary La(Fe[sub0.893]Si[sub0.107])[sub13] the magnetic entropy change for a field variation of 16 kOe and the adiabatic temperature change for a field variation of 17 kOe amounts to 21.9 J/kgK and 4.2 K at a temperature of 193 K, respectively. For this composition, the thermal and the field hysteresis were determined to be 2.5 K and 2.2 kOe, respectively. With increasing Si content the hysteresis as well as the entropy change decreases. By increasing the Co content from La(Fe[sub0.865]Co[sub0.05]Si[sub0.085])[sub13] to La(Fe[sub0.803]Co[sub0.112]Si[sub0.085])[sub13] the peak temperature of the magnetic entropy change was tailored to the commercial relevant range of 254 K-336 K. The Co-containing samples hardly showed any hysteresis at all. Such powders were pressed in a die and sintered to fully dense blocks of about 23 x 19 x 12 mm. The blocks can be machined by conventional techniques to the shapes required in magnetic refrigeration prototypes. [ABSTRACT FROM AUTHOR]