Hall effect and magnetoresistance

The two most basic electrical parameters of interest, normally, are the carrier concentration and mobility. These quantities may be obtained from the proper measurements of current, electrical field, and applied magnetic field. 

In Section 1 we will use the theory developed in Appendix A to discuss the various measurement and analysis techniques that have been applied to SI GaAs. We will also discuss the precautions that must be observed in apparatus design, and present an automated Hall-effect and photo-electronic system capable of measuring high resistivity samples. 

The first concern in performing electrical measurements on SI GaAs is, of course, the high resistances involved, say 10 SI at room temperature for a 

The second concern is the long response times that can result from typical cable and electrometer-input capacitances of 100 pF or more (RC = 1010 x 10 10 1 s). These capacitances can be effectively reduced by operating in a guarded mode, i.e., with the inner shield (say, in a triaxial cable system) driven at the same potential as that of the center conductor. (The Keithley 

602 does this automatically in its fast-feedback mode.) In this way we have been able to reduce the effective capacitance of our system to less than 1 pF. Such a scheme is especially important when carrying out ac measurements, such as ac photoconductivity. 

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Soule D. Magnetic field dependence of the hall effect and magnetoresistance in graphite single crystals. Physical Review. 1958 112(3) 698-707. 

Hall Effect and Magnetoresistance in the Relaxation-Time Approximation... 

Pig. 2.8. (a) Phase diagram of the field-induced spin density wave (FISDW) states predicted by the standard model. The dashed line indicates the experimentally supposed reentrance in (TMTSF)2C104. (b) Phase diagram of (TMTSF)2PFe obtained from Hall effect and magnetoresistance measurements at approximately 6kbar. Prom [79]... 

The resistance of structures was measured by a four-contact method simultaneously parallel and perpendicularly to the step edges of vicinal surface in the temperature interval 4.2-300 K. The Hall effect and magnetoresistance were investigated in magnetic fields up to 0.5 T. 

Indium antimonide inorg chem InSb Crystals that melt at 535°C an intermetallic compound having semiconductor properties and the highest room-temperature electron mobility of any known material used in Hall-effect and magnetoresistive devices and as an infrared detector, j in-ds-cm, an tim-3,nTd ... 

The Hall effect of boron carbide is small (Fig. 35a and b). It depends on composition and temperature (14,147-149). Because the calculation of the Hall mobility from the measured Hall constant depends strongly on the electronic transport mechanism, which for boron carbide has not yet been finally solved, the mobilities calculated after classical theories and shown in Fig. 35 are somewhat questionable. Hall effect and magnetoresistance were measured up to 15 T (Figs. 36 and 37) (157). The behavior expected from classical theory was confirmed in a large range, and for B > 13 T the magnetoresistance seems to indicate beginning Shubnikov-de Haas oscillations. The transport parameters obtained are listed in Table 3. 

Kwan CCY, Basinski J, Wooley JC (1971) Analysis of the two-rand Hall effect and magnetoresistance. Phys Status Solid 48 699-704... 

Investigations of the normal state magnetoresistance (MR) as well as the Hall effect and the thermal conductivity in the normal and superconducting mixed states give an important information about the electronic structure and the properties of vortex lattice of the investigated materials. 

Magnetic-field effects in the transport coefficients are of particular interest because of the magnetic character of the f-scattering. Due to the enhanced local susceptibility, the Hall effect and the magnetoresistance can be of anomalous size. Figure 21 shows the Hall coefficient Rn T) of CeCu in comparison with the resistivity p(T) (Milliken et al. 1988). Two main features are intriguing besides the larger size of... 

MetaUic siiicides may present both Hall effect and/or magnetoresistance [147]. Most measurements available for these properties have been obtained for thin silidde films. 

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. 

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. 

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