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Microwave Absorption (microwave + absorption)

Distribution by Scientific Domains
Physics and Astronomy100%

Kinds of Microwave Absorption

  • non-resonant microwave absorption
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    Selected Abstracts

    Microwave absorption of ferrite powders in a polymer matrix

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2006
    S. Kolev
    Abstract The object of this work is to investigate the microwave absorbing properties of nanocomposite bulk samples. As filler we used magnetite with different particle size in a silicone rubber matrix and investigated the influence of the filler concentration and particle size in the polymer matrix on the microwave nonlinearity in a large frequency range (1 ÷ 13 GHz). We found that the intensity and the frequency at the reflection loss minimum depend on the particle size and particle concentration of magnetite in the samples. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Low-field non-resonant microwave absorption in glass-coated Co-rich microwires

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009
    Raul Valenzuela
    Abstract A study of low-field non-resonant microwave absorption (LFA) at 9.8 GHz, on as-cast amorphous Co-rich CoFeBSi microwires under different measuring geometries is presented. Results confirm that LFA is associated with the magnetization processes from the unmagnetized state (HDC = 0) to the saturated condition, in many aspects similar to Giant Magnetoimpedance (GMI), and clearly different from ferromagnetic resonance (FMR). LFA signal showed large variations in its maximum,minimum separation as a function of the measuring geometry, which is interpreted in terms of the total anisotropy in the process. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Dynamics of photogenerated carriers in porous silicon probed by microwave absorption

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007
    H. E. PorteanuArticle first published online: 27 APR 200
    Abstract We report on dynamics of photogenerated carriers in porous silicon using contactless investigation tools. A comparison of two theoretical models: the simple point charge description versus degenerate gas model is presented. The temperature dependence reveals the dominant role of surface states below 70 K. Light intensity dependences evidence Auger processes. The optical and chemical properties can be indirectly improved using the microwave conductivity by studying the surface states of porous materials. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    SWNT probed by multi-frequency EPR and nonresonant microwave absorption

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2008
    B. Corzilius
    Abstract In addition to g = 2.00 signals seen frequently in EPR spectra of SWNT, signals at g = 2.07 of SWNT prepared by CVD were detected, exhibiting a Pauli susceptibility temperature dependence. This Pauli magnetism in combination with the large g shift is taken as evidence that these signals originate from itinerant electrons of metallic nanotubes. At temperatures below 150 K, a dominant narrow signal develops at g = 2.00. By applying multifrequency EPR up to 319 GHz, its inhomogeneous nature was confirmed. This signal is assigned to defects of the carbon network of the tubes. Comparing room temperature EPR spectra of CVD and arc-grown SWNT, we found a much lower concentration of metallic tubes in arc material. No g = 2.07 signals of itinerant spins could be observed, which might be also caused by the high amount of residing catalyst. A drastic increase in nonresonant microwave absorption is observed below 10 K for both types of samples, if a threshold microwave power level is passed. In the same temperature range a drop in EPR intensity is also detected. These observations are taken as evidence for a transition into a superconducting phase of part of the sample. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Electron paramagnetic resonance and non-resonant microwave absorption of single wall carbon nanotubes

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007
    B. Corzilius
    Abstract Single wall carbon nanotubes (SWNT) prepared by the "super growth" method exhibit electron paramagnetic resonance (EPR) signals, which originate from temperature activated detrapping of spins. Non-resonant microwave absorption in the temperature range below 20 K is indicative for the opening of a small gap at the Fermi level for tubes of metallic character, which might indicate a transition into a superconducting (SC) state. The expected concurrent microwave field inhomogeneity has been detected by a transient nutation experiment. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Angular and temperature-related specific features of averaging of hole effective masses in p-Ge at low temperatures

    ANNALEN DER PHYSIK, Issue 12 2009
    T. Tisnek
    Abstract Microwave magnetoresistance of lightly doped (nondegenerate) p-Ge has been studied by the electron spin resonance method, which can record the derivative of the microwave absorption with respect to the magnetic field. The change in the absorption is proportional to that in the conductivity of the semiconductor in the magnetic field (magnetoresistance). It was found that the averaging time of the light and heavy holes effective masses depends on temperature and on the magnetic field direction in a sample. An analysis of the derivative made it possible to determine regions of the fastest effective mass averaging. [source]