Magnetoresistive polyaniline/multi-walled carbon nanotube nanocomposites with negative permittivity.
Contrary to the observed positive giant magnetoresistance (GMR) in as-received multi-walled carbon nanotubes (MWNTs), pure polyaniline (PANI) synthesized with Cr(vi) as oxidant and MWNTs/PANI nanocomposites with ammonium persulfate (APS) as oxidant, a room temperature negative GMR of around -2% was reported in MWNTs/PANI nanocomposites with Cr(vi) as oxidant. Different from a frequency switch of permittivity from negative to positive in MWNTs/PANI nanocomposites with APS as oxidant, unique negative permittivity was observed in MWNTs/PANI nanocomposites with Cr(vi) as oxidant within the measured frequency range from 20 to 2 × 10(6) Hz. The obtained unique negative permittivity was explained by the plasma frequency from the Drude model, at which the permittivity changes from negative to positive and the material changes from a metamaterial to an ordinary dielectric medium. The observed positive and negative GMR behaviors in these disordered systems as verified by the temperature dependent resistivity exploration were well explained through a wave-function shrinkage model and orbital magnetoconductivity theory by calculating the changed localization length (a0).
School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China. huangyd@hit.edu.cn.
Hongbo
H
Gu
Jiang
J
Guo
Qingliang
Q
He
Yuan
Y
Jiang
Yudong
Y
Huang
Neel
N
Haldolaarachige
Zhiping
Z
Luo
David P
DP
Young
Suying
S
Wei
Zhanhu
Z
Guo
D000645:Ammonium Sulfate / Q000737:chemistry; D000814:Aniline Compounds / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D002857:Chromium / Q000737:chemistry; D008280:Magnetics; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D010539:Permeability; D013696:Temperature
D000814:Aniline Compounds; D002412:Cations; D037742:Nanotubes, Carbon; C416807:polyaniline; D002857:Chromium; C031276:ammonium peroxydisulfate; D000645:Ammonium Sulfate