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  • 1
    Electronic Resource
    Electronic Resource
    Comparison between disaccommodation and ferromagnetic resonance measurements in polycrystalline nickel ferrites (1995)
    Springer
    Applied physics 60 (1995), S. 303-307 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 76.50; 75.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. FerroMagnetic Resonance (FMR) measurements of polycrystalline nickel ferrites at 11 GHz from 77 to 400 K have been carried out. The different contributions to the FMR linewidth have been studied by a computational technique based on the parameters previously obtained for single-crystal nickel ferrite. A new qualitative comparison between the FMR and disaccommodation measurements by means of the induced anisotropy formalism is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538408
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  • 2
    Electronic Resource
    Electronic Resource
    Stretched-exponential approach in relaxing systems (1996)
    Springer
    Applied physics 63 (1996), S. 471-474 
    Details
    ISSN: 1432-0630
    Keywords: PACS02.60.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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  • 3
    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: PACS: 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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  • 4
    Electronic Resource
    Electronic Resource
    The effect of the compaction pressure on the microwave surface resistance of the Pb doped BSCCO system
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 235-240 (1994), S. 1995-1996 
    Details
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-4534(94)92219-5
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of sintering atmosphere on magnetic aftereffect in polycrystalline yttrium iron garnet samples : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6301-6303 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time effects associated with domain-wall stabilization processes are investigated at temperatures ranging from 80 to 420 K, for yttrium iron garnet polycrystalline samples sintered in different atmospheres. A very different behavior for samples sintered in high and low oxygen partial pressures is found. Above 0.1 atm the isochronal relaxation spectra show a peak around 180 K that could be associated with an electron diffusion controlled domain-wall relaxation. The activation energy for the process is close to 0.4 eV. Below this pressure, the spectra show both positive and negative peaks as a result of the competition between disaccommodation and accommodation processes. These peaks are closely temperature spaced in the neighborhood of 130 K, and the relaxation mechanism responsible for this behavior is not yet clear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352677
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison between disaccommodation and ferromagnetic resonance measurements in polycrystalline yttrium–iron–garnet samples : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5436-5438 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline yttrium–iron–garnet (YIG) samples were sintered in air at temperatures ranging from 1350 to 1450 °C. Ferromagnetic resonance measurements have been accomplished at 11 GHz from 77 to 350 K. The different contributions to the linewidth have been analyzed. These results are compared with previous measurements of magnetic disaccommodation in the same samples. A qualitative relationship between both kind of measurements for polycrystalline YIG samples by means of an induced anisotropy formalism is provided. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362331
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  • 7
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Thermal expansion of Ti-substituted barium hexaferrite (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3576-3578 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal expansion measurements in the range of 20–500 °C were carried out on both poly- and single crystalline samples of the hexagonal magnetoplumbite ferrite with composition BaTiFe11O19. The continuous scanning of the thermal expansion reveals the existence of a λ-type anomaly near the Curie temperature. In contrast to the usual observed anisotropic behavior for magnetoplumbite hexaferrites, the averaged thermal expansion coefficient for the a direction is larger than for the c direction, i.e., 12.8×10−6 and 9.5×10−6 °C−1, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372384
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  • 10
    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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