Hall effect negative

The Hall effect, an electric field perpendicular to both the impressed current flow and to the applied magnetic field, gives information about the mobility of the charge carriers as well as their sign. The Hall coefficient RH - Ey/JxHe is proportional to the reciprocal of the carrier density. The Hall coefficient is negative for electron charge carriers. 

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). 

The final transport measurement to be considered is the Hall effect. This is the most intriguing transport property, but has been so difiicult to imderstand that it has not contributed much towards the elucidation of the conduction mechanisms. The reason is that the Hall effect is anomalous and has the opposite sign from that which is normally expected. Thus holes give a negative Hall voltage and... 

M-S is an electrochemical impedance spectroscopy (EIS) technique [10-12] that can be difficult to perform and interpret if the system is not ideal. When the measurement is successful, it is able to determine both the fb and the free charge carrier density (donors or acceptors, A/Dopant) of the photoelectrode. Efb, along with the band gap (Eg) and the A dopant. can be used to determine the band structure of a photoelectrode and if it possesses the proper alignment with respect to the water splitting potentials (see chapter Introduction ). The A dopant also plays a role in the bulk and surface semiconductor properties such as the width of the depletion layer and rate of recombination. The conductivity type is also revealed by M-S analysis. The M-S plot will possess a negative slope for p-type materials and a positive slope for n-type materials (positive slope). In the case that the M-S measurement is not successful, then other techniques such as Hall Effect can still yield conductivity and A dopant for materials which can be deposited onto non-conductive substrates such as quartz. 

The atomic disorder associated with the amorphous state leads to completely different transport properties from those encountered in the crystalline state. Experimental results of the electrical resistivity, the Hall effect, magnetoresistance, thermoelectric power and the occurrence of. superconductivity are discussed in section 8. The main emphasis is placed on the electrical resistivity. The occurrence of negative temperature coefficients of the resistivity is related to models based on the extended Ziman theory. In the low temperature regime the resistivity often shows a In T... 

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