J.M. Dai

Organic photovoltaic cells with near infrared absorption spectrum

Organic photovoltaic cells with a strong absorption spectrum in the near infrared region were fabricated with the structure of indium tin oxide (ITO)/zinc phthalocynine (ZnPc)/lead phthalocynine (PbPc)∕C60∕Al. PbPc has a broad and strong absorption, while the organic films of PbPc∕C60 showed an additional new absorption peak at 900nm. The absorption in the near infrared region can harvest more photons to invert into photocurrent. Moreover, the introduction of ZnPc thin layer between ITO and PbPc further improved the new absorption peak and the collection of hole carriers at the electrode ITO, which increased the power conversion efficiencies to 1.95% and short-circuit current density to 9.1mA∕cm2 under AM 1.5 solar spectrum.

Effect of Ag substitution on the transport property and magnetoresistance of LaMnO3

Abstract The structural, magnetic and electronic properties of the polycrystalline La1−xAgxMnO3 are systematically investigated as a function of Ag-doping level. The result of the Rietveld refinement of X-ray powder diffraction shows that the samples are single rhombohedral ( R 3 C ) structure phase for x R 3 C perovskite phase and a nonmagnetic metal Ag phase. The temperature dependence of resistivity shows that all samples undergo a sharp insulator–metal (I–M) transition accompanying a paramagnetic to ferromagnetic transition with the decrease of temperature. However, for x

Large magnetic entropy change near room temperature in antiperovskite SnCMn3

We report the observation of large magnetocaloric effect near room temperature in antipervoskite SnCMn3. The maximal magnetic entropy change at the first-order ferrimagnetic-paramagnetic transition temperature (TC 279 K) is about 80.69mJ/cm3 K and 133mJ/cm3 K under the magnetic field of 20 kOe and 48 kOe, respectively. These values are close to those of typical magnetocaloric materials. The large magnetocaloric effect is associated with the sharp change of lattice, resistivity and magnetization in the vicinity of TC. Through the measurements of Seebeck coefficient and normal Hall effect, the title system is found to undergo a reconstruction of electronic structure at TC. Considering its low-cost and innocuous raw materials, Mn-based antiperovskite compounds are suggested to be appropriate for pursuing new materials with larger magnetocaloric effect.

Crystal growth and superconductivity of FeSex

In this work, crystals of FeSex have been grown by a flux approach. The crystallization process is divided into two stages. First, stoichiometric polycrystal FeSe0.82 was sintered in a solid state reaction. Then, FeSex crystals with a size about 500 µm were successfully grown in an evacuated sealed quartz tube using a NaCl/KCl flux. The products include two crystal structures: tetragonal and hexagonal. The electronic transport and magnetic property measurements show that FeSex crystals exhibit a superconducting transition at about 10 K.

Effect of Li substitution on the crystal structure and magnetoresistance of LaMnO3

The crystal structure and magnetoresistance of the polycrystalline La1−xLixMnO3 (x=0.10, 0.15, 0.20, 0.30) are investigated. The result of the Rietveld refinement of x-ray powder diffraction shows that the room temperature structural transition from rhombohedral (R3C) to orthorhombic (Pbnm) symmetry occurs at the Li-doped level x⩾0.2. Accompanying the occurrence of the structural transition, the lattice distortion and the bending of the Mn–O–Mn bond increase and the ferromagnetic transition temperature TC decreases. For x=0.10 and 0.15 samples, double metal–insulator (M–I) transitions accompanying a single ferromagnetic transition and a negative magnetoresistance as high as 26% in a magnetic field of 0.8 T are observed. For x=0.20 and 0.30, the samples manifest nonmetallic behavior throughout the measured temperature range. We suggest that the double M–I transitions phenomena of low Li-doped samples originate from the magnetic inhomogeneity due to the formations of the Mn3+ and Mn4+-rich regions induced ...

Observation of spin-glass behavior in antiperovskite compound SnCFe3

We investigated the physical properties of antiperovskite compound SnCFe3 by comprehensive magnetic measurements. The strong irreversibility is clearly observed from zero-field-cooled and field-cooled magnetizations. The peaks of ac susceptibility display strong dependences on the frequency and magnetic field. Both the magnetic relaxation effects and related analysis indicate a typical spin-glass (SG) behavior in SnCFe3. The corresponding characteristic parameters are obtained: the freezing temperature T0=20.3 K, the dynamical exponent zν=9.441, and the flipping time τ0=2.42×10−11 s. Furthermore, the Sn deficiency affects significantly the SG behavior and results in a sharp decrease in T0.

Structural, magnetic, electrical transport properties, and reversible room-temperature magnetocaloric effect in antipervoskite compound AlCMn3

We report the structural, magnetic, electrical transport properties, and magnetocaloric effect (MCE) of antipervoskite compound AlCMn3. It exhibits a second-order ferromagnetic–paramagnetic phase transition around (TC) 287 K. The electronic resistivity (ρ) shows a good metallic behavior except for a slope change around TC. At lower temperatures (below 130 K), ρ∝T2 indicates that the electron-electron scatterings domain. At evaluated temperatures (130–270 K), ρ is linear dependence on temperature, implying that the phonon scatterings boost up greatly. Furthermore, a broad distribution of the magnetic entropy change (−ΔSM) peak is found to about 100 K with the magnetic field change ΔH=45 kOe. The relative cooling power are ∼137 J/kg and ∼328 J/kg (or ∼68 K2 and ∼162 K2) with ΔH=20 kOe and 45 kOe, respectively. All these values are comparable with the typical MCE associated with a second-order transition. It suggests that AlCMn3 may be considered as a candidate material for near room-temperature magnetic ref...

Structural, magnetic, and transport properties in the Pr -doped manganites La 0.9 − x Pr x Te 0.1 MnO 3 ( 0 ⩽ x ⩽ 0.9 )

The effect of

Erasure of photoconductivity by magnetic field in oxygen-deficient La2∕3Sr1∕3MnO3−δ thin films

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Giant magnetocaloric effect and temperature induced magnetization jump in GdCrO3 single crystal

-doping on structural, magnetic and transport properties in electron-doped manganites