Abstract:An ionic liquid, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide
(TMPA TFSI), was transformed from a liquid phase to another fluidic
phase by application of the threshold magnetic field at constant temperature
(T). The magnetic-field-induced (MFI) phase transformation
was detected by the electric potential generated between two Pt electrodes
set to the bottom and upper parts in a TMPA TFSI liquid during sweep
of the magnetic field (B). The magnetic susceptibility
and Verdet constant of TM… Show more
“…We measured the Hall voltage across the channel under a constant current while sweeping the magnetic field. To avoid temporal changes in the carrier density during the measurements, all measurements were performed at temperatures below the freezing point of the ionic liquid (~ 256 K) 23 . Figure 2 FET and Hall measurements of the SWCNT thin film devices.…”
The presence of hopping carriers and grain boundaries can sometimes lead to anomalous carrier types and density overestimation in Hall-effect measurements. Previous Hall-effect studies on carbon nanotube films reported unreasonably large carrier densities without independent assessments of the carrier types and densities. Here, we have systematically investigated the validity of Hall-effect results for a series of metallic, semiconducting, and metal–semiconductor-mixed single-wall carbon nanotube films. With carrier densities controlled through applied gate voltages, we were able to observe the Hall effect both in the n- and p-type regions, detecting opposite signs in the Hall coefficient. By comparing the obtained carrier types and densities against values derived from simultaneous field-effect-transistor measurements, we found that, while the Hall carrier types were always correct, the Hall carrier densities were overestimated by up to four orders of magnitude. This significant overestimation indicates that thin films of one-dimensional SWCNTs are quite different from conventional hopping transport systems.
“…We measured the Hall voltage across the channel under a constant current while sweeping the magnetic field. To avoid temporal changes in the carrier density during the measurements, all measurements were performed at temperatures below the freezing point of the ionic liquid (~ 256 K) 23 . Figure 2 FET and Hall measurements of the SWCNT thin film devices.…”
The presence of hopping carriers and grain boundaries can sometimes lead to anomalous carrier types and density overestimation in Hall-effect measurements. Previous Hall-effect studies on carbon nanotube films reported unreasonably large carrier densities without independent assessments of the carrier types and densities. Here, we have systematically investigated the validity of Hall-effect results for a series of metallic, semiconducting, and metal–semiconductor-mixed single-wall carbon nanotube films. With carrier densities controlled through applied gate voltages, we were able to observe the Hall effect both in the n- and p-type regions, detecting opposite signs in the Hall coefficient. By comparing the obtained carrier types and densities against values derived from simultaneous field-effect-transistor measurements, we found that, while the Hall carrier types were always correct, the Hall carrier densities were overestimated by up to four orders of magnitude. This significant overestimation indicates that thin films of one-dimensional SWCNTs are quite different from conventional hopping transport systems.
“…The theoretical and experimental observations show that a first-order LLT can occur without a noticeable density change, making this phenomenon even more puzzling 19 . Furthermore, magnetic field can affect the local structure and lead to another liquid phase 20 . It was reported that an aligned liquid state of Co alloys can be transformed into another liquid phase under magnetic fields 21,22 .…”
Liquid−liquid transition (LLT) between two disordered phases of single-component material remains one of the most intriguing physical phenomena. Here, we report a first-order LLT in a series of ionic liquids containing trihexyl(tetradecyl)phosphonium cation [P666,14]+ and anions of different sizes and shapes, providing an insight into the structure-property relationships governing LLT. In addition to calorimetric proof of LLT, we report that ion dynamics exhibit anomalous behavior during the LLT, i.e., the conductivity relaxation times (τσ) are dramatically elongated, and their distribution becomes broader. This peculiar behavior is induced by isobaric cooling and isothermal compression, with the τσ(TLL,PLL) constant for a given system. The latter observation proves that LLT, in analogy to liquid-glass transition, has an isochronal character. Finally, the magnitude of discontinuity in a specific volume at LLT was estimated using the Clausius-Clapeyron equation.
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