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  • 1
    Electronic Resource
    Electronic Resource
    On the thermodynamics of the photoacoustic effect of condensed matter in gas cells (1983)
    Springer
    Applied physics 30 (1983), S. 121-129 
    Details
    ISSN: 1432-0649
    Keywords: 07.65-b ; 44.90+c
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The photoacoustic (PA) effect of condensed matter measured in a gas-microphone cell can be interpreted by the Rosencwaig-Gersho-model. This model developed originally for thermally thick gas columns is extended to arbitrary gas lengths. The periodic variation of temperature varies the internal energy of the total volume of the gas leading to a pressure oscillation by an isochoric process. Further, taking into account a residual volume as introduced by Tam and Wong, the description leads finally to an extended Rosencwaig-Gersho model (ERG). Measurements with argon (γ=1.67) and Freon 13 (CClF3, γ=1.17) for thermally thin and thick gas colomns confirm the isochoric character of the PA effect at frequencies far below the acoustic cell resonance. Experimental results of other groups can be interpreted very well with our model. Furthermore, the extended Rosencwaig-Gershomodel leads just in the low frequency region to the same results as the model of McDonald and Wetsel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695466
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of Ferromagnetic Filled Carbon Nanotubes and their Biomedical Application (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 49 (Oct. 2006), p. 74-78 
    Details
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: Especially during last years, fundamental discoveries of various species andmodifications of carbon nanotubes have stimulated research on their application including inhuman medicine. The success of these applications depends significantly on the physical,chemical and biological properties of the carbon nanotubes and their supplements.In our presentation we report on the synthesis of Fe-filled carbon nanotubes, their structuraland magnetic properties and propose novel types of such functionalised and filled multiwalledcarbon nanotubes with various advantages for an application in human medicine,especially in anti-tumour therapeutic concepts.These nanotube structures represent multi-functional nano-scaled containers for differentmedical treatments including magnetically guided hyperthermia. Furthermore these chemicalinert and stable carbon nanocontainer can be act as a new drug delivery carrier system. Inprinciple, both, a filling of nanotubes by an open-fill-close process or an attachment ofargents on the outside of the carbon nanotube is possible
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/42/transtech_doi~10.4028%252Fwww.scientific.net%252FAST.49.74.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Electronic phase separation in a low-temperature tetragonal phase of lanthanum-strontium cuprates according to 139La NQR data (1998)
    Springer
    JETP letters 67 (1998), S. 363-368 
    Details
    ISSN: 1090-6487
    Keywords: 75.60.Ch ; 75.50.Ee ; 72.80.Sk ; 76.60.Gv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A nonuniform electron density distribution is observed in La1−x− y NdySrxCuO4 and La1−x−y EuySrxCuO4, and long-lived magnetic fluctuations in these compounds are studied. The dynamics of the magnetic fluctuations depends strongly on the magnetic properties of the rare-earth ions, which stabilize the low-temperature tetragonal phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567675
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  • 4
    Electronic Resource
    Electronic Resource
    57Fe and 119Sn Mössbauer studies on La1.25Nd0.6Sr0.15CuO4: Evidence for local magnetic ordering below (approximately-equal-to)32 K (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6741-6741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 57Fe and 119Sn Mössbauer effect studies on 0.5 at. % 57Fe or 119Sn doped nonsuperconducting La1.25Nd0.6Sr0.15CuO4 in the temperature region 300 K≥T≥4.2 K reveal an onset of local magnetic ordering occurring at TM(approximately-equal-to)32 K for both 57Fe as well as 119Sn-doped samples. The local magnetic ordering shows up in the presence of a very large transferred hyperfine field of Bthf(approximately-equal-to)11.0(5) T at the 119Sn nuclei. Since such a large field is present in neither antiferromagnetic La2CuO4 superconducting La1.85Sr0.15CuO4 nor overdoped La2−xSrxCuO4 (x=0.4), the occurrence of such local spin correlations seems to be a signature of the nonsuperconducting low temperature tetragonal phase of La1.25Nd0.6Br0.15CuO4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356857
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of gas viscosity on the photoacoustic signal in gas-microphone cells (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2944-2949 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the experimentally observed variation of the phase angle cursive-phi of the photoacoustic (PA) signal as a function of coupling "gas column thickness'' for a one-dimensional PA cell. The PA signal is excited by a modulated continuous laser beam incident on an opaque solid surface, and the gas column thickness is the distance between the solid surface and the window for the incident laser beam. We show that the observed data can be explained in a PA model (called the extended Rosencwaig–Gersho model) which includes the consideration of a residual volume in the PA cell, together with the consideration of viscous damping of the PA signal at small gas column thickness. The effect of viscosity is visible already for gas column thickness of the order of magnitude of one thermal diffusion length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336957
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  • 6
    Electronic Resource
    Electronic Resource
    The charge ordered phase in studied by means of high energy X-ray diffraction (1999)
    Springer
    The European physical journal 8 (1999), S. 5-8 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 61.10.Nz Single-crystal and powder diffraction - 71.38.+i Polarons and electron-phonon interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Superstructure reflections due to charge ordering have been observed in single crystals using X-ray diffraction. The critical temperatures for the ordering process are 150 K and 180 K in samples with Sr concentrations of and , respectively. For x =0.125 the charge order transition correlates with a drastic resistivity enhancement, while a much smaller change of the resistivity is found for x = 0.15. It is argued that the onset of charge ordering in the sample with x = 0.125 is related to the suppression of co-operative Jahn-Teller distortions which is initiated by rising ferromagnetism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050662
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  • 7
    Electronic Resource
    Electronic Resource
    57Fe and119Sn Mössbauer studies on La1.25Nd0.6Sr0.15CuO4 (1993)
    Springer
    The European physical journal 92 (1993), S. 331-334 
    Details
    ISSN: 1434-6036
    Keywords: 74.25 ; 74.25 ; 76.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 57Fe- and119Sn Mössbauer effect studies on 0.5 at %57Fe (or119Sn) dopednon-superconducting La1.25Nd0.6Sr0.15CuO4 in the temperature region 300 K ≧T≧4.2 K reveal an onset of local magnetic ordering occurring atT m ≅32 K for both57Fe—as well as119Sn-doped samples. The local magnetic ordering shows up in the presence of a very large transferred hyperfine field ofB thf ≅11.0(5)T at the119Sn nuclei. Since such a large field is neither present in antiferromagnetic La2CuO4, nor in superconducting La1.85Sr0.15CuO4 or overdoped La2−xSrxCuO4 (x=0.4), the occurrence of such local spin correlations seems to be a signature of the non-superconducting low temperature tetragonal phase of La1.25Nd0.6Sr0.15CuO4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01308750
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal conductivity and thermal Hall effect in Bi- and Y-based high-T c superconductors (2001)
    Springer
    The European physical journal 20 (2001), S. 189-208 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.72.-h High Tc compounds – 74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Measurements of the thermal conductivity (kxx) and the thermal Hall effect (kxy) in high magnetic fields in Y- and Bi-based high-T c superconductors are presented. We describe the experimental technique and test measurements on a simple metal (niobium). In the high-T c superconductors kxx and kxy increase below T c and show a maximum in their temperature dependence. kxx has contributions from phonons and quasiparticle (QP) excitations, whereas kxy is purely electronic. The strong increase of kxy below T c gives direct evidence for a strong enhancement of the QP contribution to the heat current and thus for a strong increase of the QP mean free path. Using kxy and the magnetic field dependence of kxx we separate the electronic thermal conductivity ( k xx el ) of the CuO 2 -planes from the phononic thermal conductivity ( k xx ph ). In YBa2Cu3O 7 - δ k xx el shows a pronounced maximum in the superconducting state. This maximum is much weaker in Bi2Sr2CaCu2O 8 + δ , due to stronger impurity scattering. The maximum of k xx el is strongly suppressed by a magnetic field, which we attribute to the scattering of QPs on vortices. An additional magnetic field independent contribution to the maximum of kxx occurs in YBa2Cu3O 7 - δ , reminiscent of the contribution of the CuO-chains, as determined from the anisotropy in untwined single crystals. Our data analysis reveals that below T c as in the normal state a transport (τ) and a Hall ( ) relaxation time must be distinguished: The inelastic (i.e. temperature dependent) contribution to τ is strongly enhanced in the superconducting state, whereas displays the same temperature dependence as above T c . We determine also the electronic thermal conductivity in the normal state from kxy and the electrical Hall angle. It shows an unusual linear increase with temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011098
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  • 9
    Electronic Resource
    Electronic Resource
    Ising magnets with mobile defects (2002)
    Springer
    The European physical journal 30 (2002), S. 83-92 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.50.+q Lattice theory and statistics (Ising, Potts, etc.) – 74.72.Dn La-based cuprates – 75.10.Hk Classical spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Motivated by recent experiments on cuprates with low-dimensional magnetic interactions, a new class of two-dimensional Ising models with short-range interactions and mobile defects is introduced and studied. The non-magnetic defects form lines, which, as temperature increases, first meander and then become unstable. Using Monte Carlo simulations and analytical low- and high-temperature considerations, the instability of the defect stripes is monitored for various microscopic and thermodynamic quantities in detail for a minimal model, assuming some of the couplings to be indefinitely strong. The robustness of the findings against weakening the interactions is discussed as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00361-0
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal conductivity of doped $\mathsf{La_2CuO_4}$ as an example for heat transport by optical phonons in complex materials (2004)
    Springer
    The European physical journal 38 (2004), S. 37-41 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We investigate the phonon thermal conductivity $\kappa_{\mathrm{ph}}$ of doped $\rm La_2CuO_4$ based on out-of-plane thermal conductivity measurements. When room temperature is approached the temperature dependence of $\kappa_{\mathrm{ph}}$ strongly deviates from the T -1-decrease which is usually expected for heat transport by acoustic phonons. Instead, $\kappa_{\mathrm{ph}}$ decreases much weaker or even increases with rising temperature. Simple arguments suggest that such unusual temperature dependencies of $\kappa_{\mathrm{ph}}$ are caused by heat transport via dispersive optical phonons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00096-x
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