Hall coefficient measurement

Early results of Hall coefficient measurements were presented in a review article by Tanaka (78). For the La-Ba-Cu-O material as a function of the increasing fraction of barium the Hall coefficient is positive, decreasing, and nearly temperature independent above Tc. These results are shown in Figure 20. For Y-Ba-Cu-O RH increases... 

Inasmuch as the electrical resistivity peak appeared in the cooling half of the resistivity curve from incomplete cycle was not matched by any such change in the Hall coefficient measurement, the afore mentioned circumstances apply. Consequently, the band structure of TiNi can be regarded as either a simple single band or one positive band dominating over the others in the temperature being considered. This conclusion did have the support of the transport data obtained independently by other investigator [38]. 

Figure 3. Comparison for Laa-nSraCuCU between the temperatures of the pseudogap opening (T ), of the vanishing of the in-plane paraconductivity (Tc), and of the normalsuperconducting transition as observed in the resistivity measurements (Tc)- The T values are taken from the compilation in Ref. [9], and correspond to resistivity measurements (p), Hall coefficient measurements (Rh), infrared measurements (r), and static susceptibility measurements (xo)...

The resistivity along the c-axis is greater than vertical direction to the c-axis, and the hall coefficient measured with a magnetic field in the c-axis is less than that with a magnetic field vertical to the c-axis. 

The Fermi surface topology in refractory carbides has also been studied in detail. The Fermi surface in TiC was first calculated by the linear combination of atomic orbitals (LCAO) method (Em and Switendick, 1965) and then by the KKR method (Schadler, Weinberger, Klima and Neckel, 1984). It was shown that the largest sheets of the Fermi surface are hole-like in character. This contradicts the results of Hall coefficient measurements for TiC (Bittner and Goretzki, 1960 Dubrovskaya, Borukhovich and Nazarova, 1971), which clearly show the electronic character of conductivity. This contradiction was explained by calculations of the effective mass of carriers in TiC and TiN (Zhukov et al 1988a). Despite the hole character of the Fermi surface, effective masses of carriers in TiC along the main directions in the Brillouin zone appear to be positive in most cases, i.e., the electric conductivity of TiC is of electronic character. 

This very reduced AP solubility limit can be compared with the Ge" doping in In203. Hall coefficient measurements support this limit of solubility as the maximum electron concentration, 7.7 x 10 m , is... 

Hall coefficient measurements on MIECs usually reveal the properties of the more mobile electronic (electron/hole) defects. These measurements can be done for different compositions. The composition can be conveniently altered by coulometric titration or via interaction with the gas phase. Hall coefficient measurements yielding the electron or hole concentration have been reported for MnO, AgjS, AgjSe, and AgjTe. ... 

Chwang R, Smith BJ, Crowell CR (1974) Contact size effects on the van der Pauw method for resistivity and Hall coefficient measurement. Solid State Electron 17 1217-1227... 

The product composition, Tij oo2 o.ooiS2. is also consistent with the carrier concentration of 1.4 x 10 electrons/cm determined by Hall-coefficient measurements for similarly-prepared, highly stoichiometric TiS2. The carrier concentration for this extrinsic semiconductor is consistent with the contribution of four electrons per excess Ti to the host conduction band to produce its observed extrinsic semiconducting properties. ... 

Balcom, B Fischer, A Carpenter, T Hall, L, Diffusion in Aqueous Gels. Mutual Diffusion Coefficients Measured by One-Dimensional Nuclear Magnetic Resonance Imaging, Journal of the American Chemical Society 115, 3300, 1993. 

Xd is the electronic contribution to the paramagnetism, obtainable either from the ESR signal or by direct measurements with subtraction of the diamagnetic term RH is the Hall coefficient, the formula being due to Friedman (1971). K is the Knight shift, g is found to drop from 1 to about 0.3 in this range and a is then about 50 2 1 cm x. This then should mark the metal-insulator transition. A plot of g deduced from the various data is shown in Fig. 10.20. This we consider further evidence for the absence of quantum interference in liquids (Section 2). 

Fig. 2. The relationship of the true mobility ft to the measured mobility — R0a0 at various values of resistivity p0. These curves hold only for samples with negative Hall coefficients, the usual case. [From Look (1980).]...

In Part II we discussed how to measure the electrical parameters n and pn (and/or p and pp), namely, by means of the conductivity and Hall coefficient. Now we must ask how these parameters relate to the more fundamental quantities of interest, such as impurity concentrations and impurity activation energies. Much can be learned from a consideration of thermal excitation processes only, i.e., processes in which the only variable parameter is temperature. Thus, we are specifically excluding cases involving electron or hole injection by high electric fields or by light. We are also excluding systems that have been perturbed from their thermal equilibrium state and have not yet had sufficient time to return. Some of these nonequilibrium situations will be considered in Part IV. 

The variation in the measured electron mobilities from sample to sample in sintered materials (also observed by Hahn, ref. 24), may be due to any of several effects. The most probable reason for this variation in the well-sintered samples studied is a difference in history the individual samples are obtained with different numbers of conduction electrons per cm. frozen in in the necks. That is, the different history has allowed different amounts of oxygen to be adsorbed on the surface. Thus the concentration of electrons in the grain, as measured by the Hall coefficient, will have little relation to the concentration of electrons in the neck, as measured by the conductivity, and the mobility, obtained from the product of the Hall coefficient and the conductivity, will be neither the true mobility nor constant from sample to sample. The different samples may also end up with varying geometry of their necks, according to their previous treatment. 

The carrier concentration n = Nt, — and the compensation ratio 6 which were obtained by measurements of the Hall coefficient and carrier mobility, respectively, were found to be functions of Fas or Pas- The compensation ratio 0 exhibits a minimum and the carrier concentration n a maximum, at the optimum temperature 617 °C, shown in Fig. 3.47. From the compensation ratio and the carrier concentration, the concentrations of the ionized donors, A, are calculated as a function of Tas, as shown in Fig. 3.48.At the optimum temperature 617 °C, Aq shows a maximum and Aa a minimum. The total concentration of ionized impurities, N, = N/ + N, remains essentially constant in the measured Tas range. This result suggests that vacancy-related mechanisms are associated with the formation of dislocations during growth and the compensation process. Thus, high quality crystal GaAs with a low density of dislocations has been grown by precise... 

Table 1.6 compares the Hall coefficients of the elements with those of the carbides and nitrides. The Hall coefficients are obtained by measuring the transverse electrical potential in samples made to carry current in a magnetic field. The coefficient gives a measure of the carrier concentration ... 

The metallic nature of concentrated metal-ammonia solutions is usually called "well known." However, few detailed studies of this system have been aimed at correlating the properties of the solution with theories of the liquid metallic state. The role of the solvated electron in the metallic conduction processes is not yet established. Recent measurements of optical reflectivity and Hall coefficient provide direct determinations of electron density and mobility. Electronic properties of the solution, including electrical and thermal conductivities, Hall effect, thermoelectric power, and magnetic susceptibility, can be compared with recent models of the metallic state. 

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