• Title, Summary, Keyword: magnetotransport property

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Logarithmic temperature dependence of resistivity in CVD graphene

  • Takehana, Kanji;Imanaka, Yasutaka;Watanabe, Eiichiro;Oosato, Hirotaka;Tsuya, Daiju;Kim, Yongmin;An, Ki-Seok
    • Current Applied Physics
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    • v.17 no.4
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    • pp.474-478
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    • 2017
  • Logarithmical increase of the longitudinal resistivity (${\rho}_{xx}$) between 10 K and 80 K and its saturation at low temperature were observed in the graphene synthesized by the chemical vapor deposition (CVD) with various applied gate voltage. In the two-dimensional system, it is considerably difficult to identify the origin of the logarithmic temperature (Log-T) increase of the resistivity, because there are three corrections to exhibit the Log-T behavior: the weak localization, the electron-electron interaction (EEI) in the disordered system and the Kondo effect. In order to distinguish the origin of the Log-T behavior, we contrived a new method utilizing the magnetotransport property in tilted magnetic fields. As a result, we have assigned the Log-T behavior in the CVD graphene to the correction of the EEI.

Magneto-transport Properties of La0.7Sr0.3Mn1+dO3-Manganese Oxide Composites Prepared by Liquid Phase Sintering

  • Kim, Hyo-Jin;You, Jae-Hyoung;Choi, Soon-Mi;Yoo, Sang-Im
    • Journal of Magnetics
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    • v.19 no.3
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    • pp.221-226
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    • 2014
  • Significantly enhanced low-field magnetoresistance (LFMR) and maximum dMR/dH {$(dMR/dH)_{max}$} values were successfully achieved from $La_{0.7}Sr_{0.3}MnO_3$(LSMO)-manganese oxide composite samples prepared by liquid phase sintering, compared with those of the same composites prepared by solid state reaction. For this study, pure LSMO and LSMO-manganese oxide composites with various nominal compositions of (1-x)LSMO-$xMn_2O_3$ (x = 0.1, 0.2, 0.3, 0.4, and 0.8) were sintered at $1450^{\circ}C$, above the eutectic temperature of $1430^{\circ}C$, for 1 h in air. The highest LFMR value of 1.28% with the highest $(dMR/dH)_{max}$ value of 21.1% $kOe^{-1}$ was obtained from the composite sample with x = 0.3 at 290 K in 500 Oe. This enhancement of LFMR and $(dMR/dH)_{max}$ values is ascribed to efficient suppression of magnetic disorder at the LSMO grain boundary, by forming a characteristic LSMO-manganese eutectic structure.

Annealing Effect on Magneto-transport Properties of Amorphous Ge1-xMnx Semiconductor Thin Films (비정질 Ge1-xMnx 박막의 자기수송특성에 미치는 열처리 효과)

  • Kim, Dong-Hwi;Lee, Byeong-Cheol;Lan Anh, Tran Thi;Ihm, Young-Eon;Kim, Do-Jin;Kim, Hyo-Jin;Yu, Sang-Soo;Baek, Kui-Jong;Kim, Chang-Soo
    • Journal of the Korean Magnetics Society
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    • v.19 no.4
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    • pp.121-125
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    • 2009
  • Amorphous $Ge_1$_$_xMn_x$ semiconductor thin films grown by low temperature vapor deposition were annealed at various temperatures from 400 to $700^{\circ}C$ for 3 minutes in high vaccum chamber. The electrical and magnetotransport properties of as-grown and annealed samples have been studied. X-ray diffraction patterns analysis revealed that the samples still maintain amorphous state after annealling at $500^{\circ}C$ for 3 minutes and they were crystallized when annealing temperature increase to $600^{\circ}C$. Temperature dependence of resistivity measurement implied that as-grown and annealed $Ge_1$_$_xMn_x$ films have semiconductor characteristics, the increase of resistivity with annealling temperature was obseved. The $700^{\circ}C$-annealed sample exhibited negative magnetoresistance (MR) at low temperatures and the MR ratio was ${\sim}$8.5% at 10 K. The asymmetry was present in all MR curves. The anomalous Hall Effect was also observed at 250 K.