Normal Hall coefficient

Ey electric field in the y-direction Ro normal Hall coefficient... 

On lowering the temperature through Ty, a bandgap Eg = 0.1 eV appears in the FeB-ai(l) conduction band of Fig. 3 at Ep. The Hall coefficient increases as Rh exp(Ty/T), indicating that the charge-carrier density increases exponentially with T" , as in a normal semiconductor, and the Hall mobility increases from about 0.1 to 0.4 cm /Vs on lowering the temperature from Ty = 120 K to 77 K ... 

Figure 22 Temperature dependence of the Hall coefficient RH in single crystal Nd-Ce-Cu-O with Tc = 20 K. The field of 15 Tesla is applied normal to the Cu02 planes. Ref. 82.

The Hall coefficient is normal in the metallic region, but drops off as we approach the metal-non-metal transition (Fig. 10.18). It is found to be temperature-independent. 

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). 

Among the normal-state transport properties of the high-temperature cuprate superconductors, the Hall effect remains one of the most difflcult to explain. In the majority of the cuprates, the Hall coefficient Jin falls monotonically with increasing temperature. The... 

Fig. 52. Variation in Hall coefficient (normalized with respect to the initial value before hydrogenation) as a function of hydrogen concentration (Azofeifa and Clark, 2000).

Figure 3.22. Temperature dependence of the Hall coefficient for currents in the a6-plane and magnetic field normal to the plane of T-(P-5, 5-DMEDT-TTF)2(AuBr ) (AuBr2)o,75.

There are two contributions to pxy and so two terms in Eq. (22) the first one (normal HE) is caused by the Lorentz force and is proportional to magnetic induction B the second one (anomalous HE) is proportional to magnetization M (R0 and Rs are coefficients of normal and anomalous Hall effects, respectively). The second term is related to the influence of the spin-orbital interaction (SOI) on the scattering of the spin-polarized electrons and essentially exceeds the normal component [97],... 

To assign values to the molecular orbital coefficients, c, many computational methods apply Hartree-Fock theory (which is based on the variational method).44 This uses the result that the calculated energy of a system with an approximate, normalized, antisymmetric wavefunction will be higher than the exact energy, so to obtain the optimal wavefunction (of the single determinant type), the coefficients c should be chosen such that they minimize the energy E, i.e., dEldc = 0. This leads to a set of equations to be solved for cMi known as the Roothaan-Hall equations. For the closed shell case, the equations are... 

A surface heat transfer coefficient h can be defined as the quantity of heat flowing per unit time normal to the surface across unit area of the interface with unit temperature difference across the interface. When there is no resistance to heat flow across the interface, h is infinite. The heat transfer coefficient can be compared with the conductivity the conductivity relates the heat flux to the temperature gradient the surface heat transfer coefficient relates the heat flux to a temperature difference across an unknowm distance. Some theoretical work has been done on this subject [8], but since it is rarely possible to achieve in practice the boundary conditions assumed in the mathematical formulation, it is better to regard it as an empirical factor to be determined experimentally. Some typical values are given in Table 2. Cuthbert [9] has suggested that values greater than about 6000 W/m K can be regarded as infinite. The spread of values in the Table is caused by mold pressure and by different fluid velocities. Heat loss by natural convection also depends on whether the sample is vertical or horizontal. Hall et al. [10] have discussed the effect of a finite heat transfer coefficient on thermal conductivity measurement. 

The diffusion coefficient 0 2 of NH3 in air is about 0.219 cm /s at normal atmospheric pressures and room temperature. A container of ammonia is opened at the front of a lecture hall. Assuming that the air is perfectly still and that diffusion alone accounts for the transport of NH3 in the air, how long before ammonia molecules can be expected to diffuse 20.0 m away from the source ... 

Adopting the hypothesis of Trugman [60], most of the normal-state properties of the cuprates may be explained by the dressing of quasi-particles due to magnetic interactions and the subsequent modification of their dispersion relation. Then, once the quasi-particle band has been obtained, the Hall resistivity Rh = OxyzIr xxPyy can be calculated in the relaxation time approximation, using standard formulas for the transport coefficients ... 

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