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Millimeter wave (MMW) absorption measurements have been conducted on commercial samples of large (micrometer-sized) and small (nanometer-sized) particles of BaFe12O19 and SrFe12O19 using a quasi-optical MMW spectrometer and a series of backwards wave oscillators encompassing the 30–120 GHz range. Effective anisotropy of the particles calculated from the resonant absorption frequency indicates lower overall anisotropy in the nano-particles. Due to their high magnetocrystalline anisotropy, both BaFe12O19 and SrFe12O19 are expected to have spin resonances in the 45–55 GHz range. Several of the sampled BaFe12O19 powders did not have MMW absorptions, so they were further investigated by DC magnetization and x-ray diffraction to assess magnetic behavior and structure. The samples with absent MMW absorption contained primarily iron oxides, suggesting that MMW absorption could be used for quality control in hexaferrite powder manufacture. [ABSTRACT FROM AUTHOR]

DC ionization conductivity measurements were used to characterize the electrical response of amorphous semiconductors to ionizing radiation. Two different glass systems were examined: a chalcopyrite glass (CdGexAs2 for x = 0.45-1.0) with a tetrahedrally coordinated structure and a chalcogenide glass (As40Se(60-x)Tex; where x = 0-12), with a layered or three dimensionally networked structure, depending on Te content. Changes in DC ionization current were measured as a function of the type of radiation (α or γ ), dose rate, applied field, specimen thickness and temperature. The greatest DC ionization response was measured with CdGe0.85As2 at -40°C from an alpha source (which is the first reported result for radiation response from an amorphous chalcopyrite semiconductor). Avalanche gain was observed in As40Se60 with exposure to alpha radiation at fields ≥ 7 x 10³ V/cm. These results demonstrate the potential of these materials for radiation detection applications. [ABSTRACT FROM AUTHOR]