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  • AIP Publishing  (2)
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  • AIP Publishing  (2)
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  • 1
    Online Resource
    Online Resource
    AIP Publishing ; 2006
    In:  Journal of Applied Physics Vol. 100, No. 6 ( 2006-09-15)
    In: Journal of Applied Physics, AIP Publishing, Vol. 100, No. 6 ( 2006-09-15)
    Abstract: We report on a systematic study of structural, optical, electrical, and magnetic properties of Zn1−xCoxO (x=0.05–0.29) thin films codoped with Al ( & lt;0.1%). Both codoped (in which Co is cosputtered with other elements) and δ-doped (in which Co is doped digitally in the host matrix) samples have been prepared and studied. Prior to doping of Co, growth conditions were optimized to produce ZnO:Al films with a resistivity of about 1.3mΩcm. Although all the films with x in the range of 0.05–0.29 showed clear hysteresis at room temperature in magnetometry measurement and absorption peaks associated with the d-d transitions of Co2+ ions, only the most heavily doped samples have shown clear anomalous Hall effect. The latter also showed strong, but photon energy dependent, magnetic circular dichroism and negative magnetoresistance at room temperature. These results in combination with detailed structural analysis by transmission electron microscope and x-ray diffraction study revealed that the ferromagnetic properties of Zn1−xCoxO were mostly originated from secondary phases and Co precipitates. The influence of inhomogeneity on the interpretation of various measurement results is also discussed.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2006
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 2
    Online Resource
    Online Resource
    AIP Publishing ; 2017
    In:  Review of Scientific Instruments Vol. 88, No. 9 ( 2017-09-01)
    In: Review of Scientific Instruments, AIP Publishing, Vol. 88, No. 9 ( 2017-09-01)
    Abstract: Multi-frequency electrical impedance tomography has been evolving from the frequency-sweep approach to the multi-frequency simultaneous measurement technique which can reduce measuring time and will be increasingly attractive for time-varying biological applications. The accuracy and stability of the current source are the key factors determining the quality of the image reconstruction. This article presents a field programmable gate array-based current source for a multi-frequency simultaneous electrical impedance tomography system. A novel current source circuit was realized by combining the classic current mirror based on the feedback amplifier AD844 with a differential topology. The optimal phase offsets of harmonic sinusoids were obtained through the crest factor analysis. The output characteristics of this current source were evaluated by simulation and actual measurement. The results include the following: (1) the output impedance was compared with one of the Howland pump circuit in simulation, showing comparable performance at low frequencies. However, the proposed current source makes lower demands for resistor tolerance but performs even better at high frequencies. (2) The output impedance in actual measurement below 200 kHz is above 1.3 MΩ and can reach 250 KΩ up to 1 MHz. (3) An experiment based on a biological RC model has been implemented. The mean error for the demodulated impedance amplitude and phase are 0.192% and 0.139°, respectively. Therefore, the proposed current source is wideband, biocompatible, and high precision, which demonstrates great potential to work as a sub-system in the multi-frequency electrical impedance tomography system.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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