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  • 11
    Electronic Resource
    Electronic Resource
    Study of the frequency and low-field dependence of ac susceptibility in YBaCuO : 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. 7133-7135 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The frequency dependence of the ac susceptibility in polycrystalline samples of YBaCuO has been studied at the ac field range 0.06–1.2 Oe. The curve of the real part of the susceptibility χ' exhibits two drops, the first one close to Tc and the other well below Tc which could correspond to screening behavior of the grains and grain boundaries, respectively. The imaginary part of the susceptibility shows only a peak below Tc which is related to hysteresis losses at the grain boundaries. The peak corresponding to intragrains hysteresis losses is very small and appears masked by the losses of the intergrains. In the range of 1–20 kHz, the onset temperature of χ' showed no frequency dependence. However, the width of the transition decreases lightly and there is a small shift in the peak of χ‘ to higher temperature as the frequency increases. This behavior could be explained in terms of the thermally activated Anderson flux creep. The shift depends on the amplitude of the measuring field. The activation energy for flux creep ranges from 6.4 eV at 0.02 Oe to 3.23 eV at 1.2 Oe in the zero-field-cooled measurements and from 3.41 eV at 0.02 Oe to 1.41 eV at 1.2 Oe in the field-cooled measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358054
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  • 12
    Electronic Resource
    Electronic Resource
    Transport properties of amorphous CoZrNd thin films with very low Nd content (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. 6545-6545 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The composition and temperature dependence of electrical resistivity were studied for a series of amorphous (Co93Zr7)100−xNdx for x〈3.4 and for a temperature range between 77 and 300 K. The films were deposited by rf sputtering. Measurements of electrical resistivity were performed by the standard four probe technique with ac currents of 10 mA. The rate of heating and cooling was 1 K/min. The electrical resistivity is very sensitive to the presence of Nd ions, as the resistivity clearly increases with a very slight increase of Nd content. The temperature dependence of resistivity does not obey the T2 law predicted by the diffraction model as proposed by Meisel and Cote but follows very nicely the law ρ(T)=aT3/2−bT+c, a result also found for amorphous Gd–Co. The first term corresponds to the electron scattering from the magnetic spin and the second term to the electron scattering from the disordered configuration of atomic potentials. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361941
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  • 13
    Electronic Resource
    Electronic Resource
    Magnetic aftereffect and electrical conductivity in double perovskite Ba2FeMoO6 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7642-7644 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work a study of the magnetic aftereffect and electrical conductivity in Ba2FeMoO6 is presented. Aftereffect measurements have been performed by recording the time evolution of magnetic permeability just after the sample demagnetization, while the electrical conductivity has been obtained by means of the four-probe technique working under ac excitation. The isochronal relaxation spectrum was constructed by evaluating at each temperature the relative variation of permeability between the end of demagnetization and a set of indexed time windows according to the fastness of the magnetic relaxation. The magnetic aftereffect spectra show two well-defined peaks related to the magnetic phase transition and the orientational processes that can be fitted by activation energies close to 0.65 eV. Electrical conductivity presents metallic behavior in the ferromagnetic region and semiconducting response in the paramagnetic zone with activation energy of 0.03 eV. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356051
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  • 14
    Electronic Resource
    Electronic Resource
    An approach to the magnetic disaccommodation in Ti-substituted Ba–W hexaferrites (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6250-6252 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relaxation of the initial permeability has been measured in polycrystalline Ti-doped Ba–W hexaferrites with nominal composition BaTixFe18−xO27, with x ranging among x=0 and 0.3. The samples have been sintered at different temperatures in the 1250 °C〈T〈1350 °C range in a reducing CO2 atmosphere and rapidly quenched to promote the presence of crystal vacancies. X-ray diffraction spectra reveal the presence of hexaferrite as main phase. In the temperature range between 80 and 500 K, the time decay of the initial permeability after sample demagnetization has been plotted by means of isochronal curves. The isochronal disaccommodation spectra show an increase in the amplitude of the different disaccommodation peaks in substituted samples regarding pure Ba–W hexaferrites. These peaks are centered at 180, 300, and 380 K and they are related to the presence of both ferrous cations and lattice vacancies. The increase of the disaccommodation maxima in Ti-substituted hexaferrites is ascribed to the additional amount of ferrous cations induced by the presence of Ti cations, in order to maintain electrical neutrality. On the other hand, the isochronal spectrum in pure Ba–W shows another relaxation peak at 240 K which almost disappears in substituted hexaferrites, even with the lowest Ti doping analyzed. This behavior is explained in terms of the increasing hindrance to the mechanisms responsible for this ionic relaxation process, owing to the site occupation by the nonmagnetic Ti cations within the hexagonal structure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372670
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  • 15
    Electronic Resource
    Electronic Resource
    Magnetic disaccommodation in single yttrium iron garnet crystal (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 564-565 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of magnetic disaccommodation in single yttrium iron garnet (YIG) crystals are presented. Two peaks of 0.2%–0.3% are observed in the isochronal spectrum around 130 and 250 K. Comparison of our results with those on polycrystalline YIG samples and with similar data on illuminated and gamma ray irradiated single YIG crystal samples is provided. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116401
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  • 16
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    Unknown
    Ordenación, planificación y gestión del espacio litoral (1995)
    Madrid : Periodicals Archive Online (PAO)
    Estudios geográficos. 56:220 (1995:jul./sept.) 623 
    Details
    ISSN: 0014-1496
    Topics: Geography
    Notes: Bibliografía
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:6094-1995-056-20-000007
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  • 17
    Electronic Resource
    Electronic Resource
    Hypertensin: The Substance Causing Renal Hypertension (1939)
    [s.l.] : Nature Publishing Group
    Nature 144 (1939), S. 980-980 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] AN increase in blood pressure is produced by compression of the renal artery1 or by injection of the venous blood of the kidneys2. The nitrate obtained after adding 3 vol. of acetone to the serum of this blood contains a pressor substance which is insoluble in ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/144980a0
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  • 18
    Electronic Resource
    Electronic Resource
    Magnetic disaccommodation in normal spinel structures (1991)
    Springer
    Applied physics 52 (1991), S. 242-246 
    Details
    ISSN: 1432-0630
    Keywords: 75.60 ; 76
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Magnetic disaccommodation is investigated for ferrous ferrites with normal spinel structure. This study shows the presence of a new relaxation process in the temperature region IV (≃285 K) that has not been detected in inverse spinels. A numerical analysis of the isochronal spectra reveals that it is composed of two simple Debye processes with activation energies close to 0.75 eV and 0.80 eV, and preexponential factors 3×10−13 s. This relaxation is attributed to the formation of an induced anisotropy due to jumps of B-Fe ions into vacancies (as process III), but in presence of a divalent cation occupying an A-site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324585
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  • 19
    Electronic Resource
    Electronic Resource
    The dilution of silica in a NiZnCo spinel ferrite matrix (1996)
    Springer
    Applied physics 63 (1996), S. 453-459 
    Details
    ISSN: 1432-0630
    Keywords: 75.60E ; 75.60L ; 82.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Silica may dissolve up to about 0.05 wt% in an iron excess NiZnCo spinel matrix, affecting noticeably the magnetic properties at low and high values of the applied field. The initial permeability is reduced by about 50% with the addition of only 0.1 % SiO2, while the coercivity almost triples, without noticeable changes in porosity or grain distribution. The vacancy and Fe2+ content of the sintered material also show a considerable change. The energy associated to the transformation Fe3+ → Fe2+ for the samples without SiO2 was found to be 0.41–0.42 eV, while for the samples with SiO2 additions it decreased to 0.26 eV. The changes in magnetic properties are thought to be caused, more than because of the mentioned changes in ion distribution, by the stresses and defects created in the lattice due to the very small size of the Si4+ ion, which substitutes Fe3+ ions in tetrahedral sites. The transition Fe3+ → Fe2+ seems to take place exclusively in the octahedral sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571673
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  • 20
    Electronic Resource
    Electronic Resource
    Stretched-exponential approach in relaxing systems (1996)
    Springer
    Applied physics 63 (1996), S. 471-474 
    Details
    ISSN: 1432-0630
    Keywords: 02.60.Ed ; 75.60.L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The stretched-exponential or Kohlrausch-Williams-Watts function has been widely used in the description of a large variety of relaxation phenomena in condensed matter physics. In this work, we consider this approach as a fundamental law and extend its applicability range to thermally activated relaxation processes. A non-iterative and robust technique is developed in order to obtain the characteristic parameters of this type of phenomena. The method is based on a set of closed-form expressions for the amplitude, activation energy, pre-exponential factor and stretched-exponent that can be directly computed from isothermal curves. This strategy is applied to describe the magnetic disaccommodation spectra observed around room temperature in a magnetite sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571676
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