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  • 1
    Electronic Resource
    Electronic Resource
    Large room-temperature magnetoresistance and phase separation in La1−xNaxMnO3 with 0.1≤x≤0.3 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2943-2948 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural, magnetic, and electronic properties of the polycrystalline La1−xNaxMnO3 (x=0.10, 0.15, 0.20, and 0.30) are investigated. The result of the Rietveld refinement of x-ray powder diffraction shows that these compounds crystallize in a rhombohedrally distorted structure with space group R3¯C. The magnetic measurement shows that Curie temperature TC of the studied samples is near or above room temperature. The temperature dependence of resistivity shows that all samples undergo a sharp transition accompanying a paramagnetic to ferromagnetic with the decrease of temperature, however, for x≥0.15 samples, double transition peaks with a single ferromagnetic transition is observed. In the meanwhile, a large room-temperature magnetoresistance with low applied magnetic field is observed. The co-existing ferromagnetic metallic phases and ferromagnetic insulating (FMI) phases induced by the electronic inhomogeneity as well as the additional FMI phases caused by the presence of vacancies at the A sites, are presented to account for the transport properties and large magnetoresistance in these compounds. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1396823
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Li doping on the charge ordering state of La0.5Ca0.5MnO3 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7419-7421 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of Li doping on the charge ordering (CO) state in perovskite-type manganates La0.5Ca0.5−xLixMnO3 with x=0, 0.05, 0.1, 0.15, 0.2 is investigated by transport and magnetic property measurements. The resistivity of the samples decreases with the increase of the Li-doped level. As x≥0.1, the insulator–metal (IM) transition has been induced. Accompanying the variation of transport properties, the sample undergoes the variation from antiferromagnetic order for x〈0.05 to ferromagnetic (FM) order for x≥0.1. The experimental results indicate that the Li doping can destroy the CO state and induce the FM metallic (FMM) phase. These phenomena can be interpreted in terms of the strong competition between the CO state and FM phase induced by the Li+ ions substitution for the Ca2+ ions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1358346
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  • 3
    Electronic Resource
    Electronic Resource
    Visible-light-induced persistent photoconductivity in perovskite manganite films of (La0.3Nd0.7)2/3Ca1/3MnO3 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3118-3120 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The persistent photoconductivity (PPC) induced by visible light of a He–Ne laser with a wavelength of 632.8 nm in perovskite manganite films of (La0.3Nd0.7)2/3Ca1/3MnO3 at low temperatures, below ∼50 K, was observed. Based on the measurements of transport and magnetic properties, it is suggested that the samples undergo a transition of cluster-glass state below ∼50 K. The PPC phenomenon can be qualitatively explained in terms of a photoinduced ferromagnetic cluster growth model. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1391415
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  • 4
    Electronic Resource
    Electronic Resource
    Visible-light induced persistent photoconductivity in trilayered films of perovskite manganites (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6967-6969 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The persistent photoconductivity (PPC) effect has been observed in trilayered films made of perovskite manganites La2/3Ca1/3MnO3/(La0.3Nd0.7)2.3Ca1/3MnO3La2/3Ca1/3MnO3(LNL) induced by He–Ne laser with wavelength of 632.8 nm. According to the result obtained in the thin film of (La0.3Nd0.7)2/3Ca1/3MnO3(LNCMO), which the PPC effect is also observed below ∼50 K, the PPC effect observed in trilayered film LNL should originate from the middle layer LNCMO. Compared with the thin film of LNCMO, the PPC effect of the trilayered film LNL appears at ∼86 K, which is higher than that of LNCMO at ∼50 K. The PPC effect of LNL can be quenched on thermal cycling in the vicinity of 98 K, which is also higher than that of LNCMO at ∼77 K. The difference of PPC behavior between the thin films of LNCMO and LNL can be attributed to the variation of cluster-glass state in the trilayered films of LNL caused by the strong coupling of interlayer between the middle layer LNCMO and the top/bottom layers LCMO. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1358334
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Li substitution on the crystal structure and magnetoresistance of LaMnO3 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5915-5919 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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 (R3¯C) 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 by partial substitution of the monovalent Li1+ ions for the trivalent La3+ ions. The transport property of high Li-doped samples (x=0.20 and 0.30) can be explained according to the additional localization of eg electrons induced by a static coherent Jahn–Teller distortion of the MnO6 octahedra stemming from the structural transition from rhombohedral (R3¯C) to orthorhombic (Pbnm) and the reduced bandwidth of eg electrons due to the increased bending of the Mn–O–Mn bond. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319971
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  • 6
    Electronic Resource
    Electronic Resource
    Structural, magnetic, and transport properties in a Cu-doped La0.7Ca0.3MnO3 system (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6263-6267 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural, magnetic, and transport properties of La0.7Ca0.3Mn1−xCuxO3 (0≤x≤0.2) have been investigated. The maximum magnetoresistance (MR) is about 4×106% for the sample with x=0.15, which is about ∼104 times the maximum MR for samples with x≤0.1. A change in the structural parameters and magnetic and resistivity properties of the samples shows that Cu exists in Cu3+ ionic form in the sample with x≤0.05. However, Cu2+ ions begin to appear and then they increase with further Cu doping. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415757
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  • 7
    Electronic Resource
    Electronic Resource
    Unipolar arc simulation device (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3583-3585 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a simple laboratory device for establishing a vacuum arc plasma discharge that can serve to simulate a unipolar arc. The technique makes use of a triggered vacuum arc plasma gun to generate a plasma plume that in turn causes breakdown of a secondary discharge. The device is in fact a secondary vacuum arc discharge that is triggered by a primary vacuum arc discharge, with some of the features of the secondary plasma discharge having similarities with a unipolar arc configuration. Here we describe the experimental setup and outline how the device can be used for some areas of unipolar arc materials research. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149963
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  • 8
    Electronic Resource
    Electronic Resource
    Enhanced intergrain tunneling magnetoresistance in double perovskite Sr2FeMoO6 polycrystals with nanometer-scale particles (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3853-3855 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline ordered double perovskite Sr2FeMoO6 bulk samples with grain size in the range of 29–45 nm have been synthesized at temperatures from 900 to 1000 °C, using a sol-gel method. We find that the intergrain magnetoresistance is closely correlated with the grain size. The sample with the grain size of 29 nm shows large magnetoresistance Δρ/ρ0, 30%–20% at a low magnetic field of 4 kG over a wide temperature range from 20 to 300 K. The results can be explained in terms of spin-dependent intergrain tunneling model. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125478
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  • 9
    Electronic Resource
    Electronic Resource
    Second-order, high-temperature superconducting gradiometer for magnetocardiography in unshielded environment (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 906-908 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By employing high-temperature superconducting quantum interference device (SQUID) magnetometers, we have assembled a second-order gradiometer for magnetocardiography (MCG) in unshielded environment. With this high-temperature superconductor (HTS) SQUID system, we demonstrated its diagnostic relevance for MCG in terms of signal-to-noise ratio, spatial resolution, frequency bandwidth, rejection of environmental disturbances, and long-term stability. The electronically balanced gradiometer consists of three HTS radio-frequency SQUIDs with superconducting coplanar resonators, mounted in axial gradiometric arrangement with a baseline of 7.5 cm. The system achieves a common mode rejection for axial homogeneous fields of about 104 without any mechanical balancing, and a white noise about 130 fT/(square root of)Hz at 77 K, with an 8×8 mm2 flux pickup area. MCG maps above volunteers' chests have been recorded in unshielded environment in a bandwidth of about 130 Hz. We showed the influence of several notch filters (suppressing the power line frequency) on the quality of the MCG signals. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125625
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  • 10
    Electronic Resource
    Electronic Resource
    Density functional calculations of lanthanide oxides (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 9296-9308 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Density functional (DF) calculations have been performed on LaO, EuO, GdO, YbO and YbF. Gradient-exchange and correlation functionals work satisfactorily in the outer valence shells of these molecules, but less well for the localized lanthanide f-shells. Relativistic corrections to bond lengths, bond energies and vibrational frequencies are of quite different magnitudes and origins. The inner Ln 4f-shell has a fractional electron population in several molecular states. We corroborate the assignment of the 0+ ground state of YbO as configuration mixed Yb2+(f14/f13s)O2−. The effective charge distribution of the lanthanide oxides is at best approximated by Ln+O−. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468796
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