Hall effect temperature-dependent

Temperature dependent Hall effect measurements have also been carried out in the temperature range 30 to 260 K on a K3C60 thin film [116]. For three... 

Song et al. [16] reported results relative to a four-point resistivity measurement on a large bundle of carbon nanotubes (60 um diameter and 350 tm in length between the two potential contacts). They explained their resistivity, magnetoresistance, and Hall effect results in terms of a conductor that could be modeled as a semimetal. Figures 4 (a) and (b) show the magnetic field dependence they observed on the high- and low-temperature MR, respectively. 

Wang, Z., Brawner, D., Chien, T., Ong, N., Tarascon, J., and Wang, E., Temperature Dependent Hall Effect in Nd2 xCex-Cu04 and "60 K" YBa2Cu3Oy Single Crystals, International M2S-HTSC Conference, Stanford, CA, 3-28 July 1989, to be published Physica C. 

Fig. 5. Energy above the valence band of levels reported in the literature for GaP. Arrangement and notations are the same as in Fig. 4. Abbreviations for experimental methods not defined in Fig. 4. are temperature dependence of resistivity (RT), temperature dependence of minority-carrier lifetime (LT), Hall effect (H), and photostimulated electron paramagnetic resonance (PEPR).

Temperature-Dependent Hall-Effect Parameters in Semi-Insulating GaAs ... 

Finally, the reliability of the various activation energy measurements should be judged. The TDH measurement is unambiguous as long as the Hall factor [Eq. (A17)] is either close to unity or else is not very temperature dependent (or both), and if mixed conductivity effects are either small or can be taken into account. Usually, neither of these problems is very important as far as a major change in the slope of the Arrhenius plot is concerned. The emission experiments, on the other hand, lead to an apparent activation energy of Ei0 + Eai, where Eai is given by the relationship [Pg.122]

These results indicate that surface effects were not affecting his results to any extent at temperatures below room temperature. If surface traps had been involved, they would have affected the conductivity of sintered samples to a larger extent than the Hall coefficient. However, the temperature dependence of the Hall coefficient corresponds closely to that of the conductivity. 

Fig. 37. Band edge profile of a (In,Mn)As/GaSb heterostmcture. Eq. E. and Ep denote band edges of conduction band, valence band, and Fermi level, respectively, (b) Temperature dependence of the magnetization observed during cooldown in the dark (open circles) and warmup (solid circles) under a fixed magnetic field of 0.02 T. The effect of light irradiation at 5 K is also shown by an arrow, (c) Magnetization curves at 5 K observed before (open circles) and after (solid circles) light irradiation. Solid line shows a theoretical curve, (d) Hall resistivity />Hall observed at 5 K before (dashed line) and after (solid line) light irradiation (Koshihara...

Fig. 38. Hall resistance Rnall of an insulated gate (ln.Mn)As field-effect transistor at 22.5 K as a function of the magnetic field for three different gate voltages. /tnaii s proportional to the magnetization of the (In.Mn)As channel. Upper right inset shows the temperature dependence of / Hall- Let inset shows schematically the gate voltage control of the hole concentration and the conesponding change of the magnetic phase (Ohno et al. 2000).

The Hall effect has been studied only for some borocarbides. The normal state Hall coefficients / h were found to be negative and only weakly temperature dependent for polycrystalline borocarbides based on R = Y (Fisher et al. 1995 Narozhnyi et al. 1996 Mandal and Winzer 1997), La (Fisher et al. 1995), Ho (Fisher et al. 1995 Mandal and Winzer 1997) and Gd (Mandal and Winzer 1997). A negative but strongly temperature dependent R was found for the heavy-fermion compound YbNi2B2C (Narozhnyi et al. 1999b). 

Analysis of Hall-effect data has been one of the most widely used techniques for studying conduction mechanisms in solids, especially semiconductors. For the single-carrier case, one readily obtains carrier concentrations and mobilities, and it is usually of interest to study these as functions of temperature. This can supply information on the predominant charge-carrier scattering mechanisms and on activation energies, i.e., the energies necessary to excite carriers from impurity levels into the conduction band. Where two or more carriers are present, the analysis becomes more complex, but much more information can be obtained from sludies of the temperature and magnetic held dependencies. 

Special attention is paid to transport properties (resistance and Hall effect) because they are very sensitive to external parameters being the base for working mechanisms in many types of sensors and devices. The magnetic field and temperature dependences of resistance and Hall effect are considered in the framework of the percolation theory. Various types of magnetoresistances such as giant and anisotropic ones as well as their mechanisms are under discussion. 

New very promising possibilities have opened by recently observed quantum effects in nanogranular metals described partly in Section 6. But much more detailed knowledge is needed for their use, so studies on these effects should be continued. Also, some problems known to be unsolved for a long time, such as the temperature dependence of electrical conductivity and a reason for the Hall effect, are also looking for their solution. The affect of shape distribution on magnetic, electrical, optical and relaxation processes is not clear today in detail the task appears to be too sophisticated but it should be solved at least by computer simulation. 

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