Showing papers on "Colossal magnetoresistance published in 1977"
TL;DR: In this paper, the authors measured the electrical resistance as a function of applied electrostatic charge, known as the field effect, in Bi wires ranging in size from 2.6 to 29 \ensuremath{mu}m.
Abstract: The change in the electrical resistance as a function of applied electrostatic charge, known as the field effect, has been measured in Bi wires ranging in size from 2.6 to 29 \ensuremath{\mu}m. These measurements were made at 4.2 K in the presence of applied magnetic fields of varying strengths and directions. The changes in resistance of the samples as a function of applied parallel magnetic field, in fields up to 7 \ifmmode\times\else\texttimes\fi{} ${10}^{5}$ A/m, have been analyzed as a combination of the bulk longitudinal magnetoresistance and a decrease in the amount of surface scattering. Simultaneous measurements of the field effect in these magnetic fields show, in general, a decrease in the field effect as the surface scattering decreases. When the applied magnetic fields are not parallel to the sample axis the magnetoresistance data indicate increased surface scattering, and an increase in the size of the field effect is also seen. These results are interpreted as suggesting that a major contribution to the field effect in our samples is due to changes in the surface scattering of the intrinsic carriers caused by the added charge. The magnetoresistance data allow us to estimate the specularity coefficient $p$ for two samples to be 0.33 and 0.41, and the change in $p$ with added charge to be 0.1 ${(\mathrm{C}/{\mathrm{m}}^{2})}^{\ensuremath{-}1}$ and 0.3 ${(\mathrm{C}/{\mathrm{m}}^{2})}^{\ensuremath{-}1}$.
27 citations
13 citations
TL;DR: In this article, an extensive experimental investigation of the negative magnetoresistance phenomenon in a non-crystalline carbon has been carried out, where the microstructure of the material was altered by heat treating in the range 1000°−2800°C, and the effect of the changes induced was measured as a function of temperature (10−300 K) and magnetic field (0−50 kG).
Abstract: An extensive experimental investigation of the negative magnetoresistance phenomenon in a non-crystalline carbon has been carried out. The microstructure of the material was altered by heat treating in the range 1000°−2800°C, and the effect of the changes induced was measured as a function of temperature (10–300 K) and magnetic field (0–50 kG). The negative magnetoresistance was found to follow a f(H/T 1/2) dependence over a large range of temperatures and magnetic fields. The mechanism is thought to be spin-flip scattering from localized spins. Starting with Δρ∞ −m 2, where m is the magnetic moment per localized spin, the discussion relates the observed negative magnetoresistance to the anomalous behaviour of the spin susceptibility on the metallic side of the metal-insulator transition.
9 citations
TL;DR: In this article, the authors measured the transverse magnetoresistance of GaAs with enough Mn or Ni acceptors to result in activationless impurity conduction, and showed that the negative magnetoreduction is the algebraic sum of an increasing positive term and a saturating type negative component.
Abstract: Transverse magnetoresistance was measured, from 20 to 30 K and for fields up to 1 T, in GaAs crystals doped with enough Mn or Ni acceptors to result in activationless impurity conduction. Anomalies in the weak‐field magnetoresistance were seen in the impurity conduction range. Nickel‐doped samples showed consistently zero or positive Δρ/ρo, though the near‐zero magnetoresistance below 0.5 T for the temperature range 40–100 K suggested cancellation of conventional monotonically increasing positive magnetoresistance by a negative component that saturated for large fields. With manganese‐doped crystals, a small negative total magnetoresistance (−Δρ/ρo<4×10−5) was seen for fields up to 0.6 T, but only within the limited temperature range 40–75 K. The field dependence again suggested that total magnetoresistance should be regarded as the algebraic sum of an increasing positive term and a saturating‐type negative component. The magnitude and field dependence of the negative magnetoresistance of GaAs : Mn was co...
4 citations
01 Jan 1977
TL;DR: The effect of the crystal field levels on the magnetoresistance of Pr is calculated numerically on a simple model and agreement is shown with experimental measurements at 4.2K up to 20 tesla.
Abstract: The effect of the crystal field levels on the magnetoresistance of Pr is calculated numerically on a simple model and agreement is shown with experimental measurements at 4.2K up to 20 tesla. Results at higher temperatures are discussed.