Mechanism of electrical conductivity in Nickel-Iron Ferrite

Measurements of the frequency dependence of the dielectric conductivity, Hall mobility, and thermal EMF as a function of temperature on polycrystalline Ni
0.6
Fe
0.4
Fe
2
O
4
indicate that these data can be interpreted in terms of the band model. Previous analyses of the semiconductor properties of ferrites according to the hopping model assume that the number of carriers
n
is identical with the concentration of divalent iron ions. Hall measurements indicate that this is not the case here, and that
n
is best described by the equation
n^{2} = (N_{D}-n)N_{0}[\frac{m*}{m}]^{3/2} g^{-1} \exp (\frac{-E_{D}}{kT})
. Assigning a value of 2 to
g , m*/m
is 9.3, and E
D
is 0.034 eV.