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  • 1
    Electronic Resource
    Electronic Resource
    Lattice effects on the magnetoresistance in doped manganese perovskites (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4541-4541 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study of doped LaMnO3 with fixed carrier concentration has revealed a direct relationship between the Curie temperature Tc and the average ionic radius of the La site 〈rA〉, which is varied by substituting rare earths of different ionic radii for La. With decreasing 〈rA〉 magnetic order and significant magnetoresistance occur at lower temperatures with increasing temperature hysteresis, and the magnitude of the magnetoresistance increases dramatically. The predominant structural effect of decreasing 〈rA〉 is to decrease the Mn–O–Mn bond angle, which is accompanied by slight variations in the Mn–O bond distance. These results demonstrate that the notion of "double exchange'' must be generalized to include changes in the Mn–Mn electronic hopping element as a result of microstructural changes induced by composition, temperature and pressure variations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361716
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  • 2
    Electronic Resource
    Electronic Resource
    Small angle neutron scattering from the vortex lattice in 2H-NbSe2 (invited) (abstract) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6789-6789 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on small angle neutron scattering studies of the flux-line lattice in single crystal 2H-NbSe2. For fields inclined with respect to the c axis, we find distortions and form factors consistent with Ginzburg–Landau corrections to the London equations with a mass anisotropy Γ=10.1±0.9. The flux lattice orientation, however, remains pinned to the crystal lattice for all tilts studied, in disagreement with the orientation defined by anisotropic London theory. For fields below 2 kG parallel to the c axis, the peaks are no longer resolution limited. The correlation lengths extracted are history dependent, and show that the lattice is annealed when a current greater than the critical current is applied. This occurs both when a direct transport current is used, or an induced current in a zero field cooled experiment. The annealing is seen in both the transverse and longitudinal correlation lengths, and calls into question the relationship between the Larkin–Ovchinnikov correlation length and the measured critical currents in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358130
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  • 3
    Electronic Resource
    Electronic Resource
    The P-T magnetic phase diagram of SmMn2Ge2 (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4237-4239 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SmMn2Ge2 shows reentrant ferromagnetism. Using flux grown single crystals we find that on cooling through the Curie temperature (Tt1=350 K) the material becomes ferromagnetic (FM). Upon further cooling, at Tt2=150 K an antiferromagnetic (AFM) phase is reached which is stable until Tt3=100 K when there is a transition to FM. The transitions at Tt1 and Tt2 are first order with a temperature hysteresis of about 4 K. Using ac susceptibility to determine the various transition temperatures as a function of pressure (P) we find that Tt3 rapidly decreases with increasing P and at relatively low pressures falls below our measuring range (90 K). Tt2 increases nearly linearly with P and reaches 330 K and 11 kbar. Tt1, drops slowly with increasing P and at 11 kbar the high temperature FM region ends. An x-ray determination of the lattice parameters (at atm pressure) shows that in the AFM region the a0 lattice parameter is decreased, discontinuously changing at Tt2 and Tt3. The c0 lattice parameter is essentially unchanged going through this transition region. These observations indicate that the magnetic properties of SmMn2Ge2 are very sensitive to interatomic spacing. Measurements with a differential scanning calorimeter show that, on heating, the transition at Tt2 is endothermic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338485
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  • 4
    Electronic Resource
    Electronic Resource
    Trapping in organic field-effect transistors (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 336-342 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Current–voltage characteristics of single- and polycrystalline organic field-effect transistors are analyzed. The effect of bulk, interface, and grain boundary traps is investigated. The frequently observed dependence of the field-effect mobility on the gate voltage is ascribed to trapping processes rather than to an intrinsic charge transport mechanism in these organic semiconductors. Furthermore, the thermally activated mobility in polycrystalline devices, frequently observed, is ascribed to the formation of a potential barrier at the grain boundaries of the polycrystalline semiconductor. The barrier height depends significantly on the trap density and the position of the Fermi energy and therefore on the gate voltage. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329667
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic properties of epitaxial-doped manganite multilayer films (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4953-4953 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated and studied the structure and magnetic properties of high quality single crystalline (La0.7Ca0.3)MnO3 and (La0.7Ba0.3)MnO3 films. Films were grown on SrTiO3 as well as LaAlO3 substrates. (La0.7Ca0.3)MnO3 and (La0.7Ba0.3)MnO3 films grown on SrTiO3 exhibit excellent crystallinity and magnetic properties while those grown on LaAlO3 show mediocre structural and magnetic properties. These differences indicate the importance of lattice match and structural similarity between the film and the substrate. X-ray and Rutherford backscattering analysis provide a consistent picture of the structural properties of these doped manganite films. These films enable us to investigate the crystal anisotropy using vibrating sample magnetometry and torque magnetometry. Multilayers composed of manganite layers with different dopants (e.g., calcium and barium dopants) also have excellent structural properties since there is minimal strain at the interfaces. Such isostructural single crystalline multilayers are essential for investigating exchange coupling of the doped manganites.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365009
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  • 6
    Electronic Resource
    Electronic Resource
    Anisotropic (triplet) superconductivity in UPt3 (invited) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3060-3063 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrasound experiments were performed on single crystals of the heavy Fermion superconductor UPt3. From the ultrasound attenuation below Tc, a quasiparticle density of states linear in energy is deduced, which we interpret as due to an anisotropic polar-like (triplet) superconducting state. This is further supported by the agreement of the only fitting parameter Δ0/kTc with the theoretical value for polar p-wave pairing. The attenuation in the normal state gives the electron-phonon interaction strength and the product of the deformation potential times the effective mass is found to be the same as for ordinary "light'' Fermion systems. The observed variations of the sound velocity are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335213
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  • 7
    Electronic Resource
    Electronic Resource
    High-resolution pressure–volume measurements by a strain gauge technique (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 459-461 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An experimental technique is described which employs resistive strain gauges to measure the pressure–volume relationship of solids up to∼50 kbar. The strain resolution is better than 10 ppm with a dynamical range up to 20 000. Two examples are presented to illustrate the sensitivity and the reliability of this technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138322
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of the induced moment magnetic form factor of a heavy fermion superconductor (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3087-3089 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarized neutron scattering techniques have been used to study the spatial distribution and temperature dependence of the magnetization induced in a single crystal sample of CeCu2Si2 by a magnetic field of 50 kOe. We find that at 4.2 K (〉Tc), the induced magnetization is predominantly of 4f electronic character. No evidence was found of any change in the magnetic form factor between 300 and 4.2 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335168
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  • 9
    Electronic Resource
    Electronic Resource
    Low temperature resistivity of Ce-La-Th under pressure (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3131-3133 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low temperature resistivity of Ce0.9−xLaxTh0.1 alloys is known to vary as ρ0+αT2. We have investigated the variation of ρ0 and α with pressure for several concentrations x. An unusually strong nonlinear decrease of the residual resistivity with pressure occurs; the magnitude of the decrease is an order-of-magnitude larger than in the isostructural nonmagnetic alloy La0.8Th0.2. The temperature coefficient α(P) also decreases strongly. These results are in qualitative accord with recent theories of the resistivity of disordered valence fluctuation compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335181
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  • 10
    Electronic Resource
    Electronic Resource
    Spin resonance in EuxSr1−xS with x=0.4, 0.5, and 0.54 (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3488-3490 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron spin resonance has been studied in single crystal spheres of EuxSr1−xS with samples of nominal composition x=0.4, 0.5, and 0.54. The emphasis has been on the field for resonance of x=0.4 material at 11.65 GHz at temperatures between 4.2 and 1.65 K. Even at the lowest temperatures the lines do not vary with crystal orientation. In all samples there is a depression of the field for resonance beginning at about 10 K, and increasing to the lowest temperatures. This is interpeted as an "internal'' field Hi. Measurements at 17 GHz reveal that Hi for all three compositions decreases with increasing frequency. Surprisingly, at 1.65 K, this seems to vary with sphere size for the x=0.4 composition. In addition to the experiments on spheres, a small plate-shaped specimen of x=0.4 was studied. It too showed a large depression of the field for resonance at 1.75 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335035
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