For a particular material the Hall coefficient was found to be zero. The material is

Hall coefficient is defined as: ρc = charge density σn = nμnq and σp = Pμpq Hall coefficient depends on the hole and electron concentration, and also on the mobility of carriers. In a metal, the gap between the conduction band and the valence band is very low. The concentration of ions (n) is very high in metals. So, the Hall coefficient will be zero almost for the metal as the Hall coefficient is inversely proportional to the concentration (n).

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