The Magnetic Susceptibility of Semiconductors with Nonparabolic Energy Bands

Formulae for the Pauli paramagnetic susceptibility, and the Landau‐Peierls diamagnetic susceptibility, due to free carriers in an arbitrary spherical energy band are derived. It follows from these formulae that nonparabolicity of a band can have a considerable influence on the susceptibility. A reversal of sign can even occur if the nonparabolicity is strong enough. The formulae reduce to the well‐known expressions if the band is parabolic. A qualitative agreement with experimental results is obtained for InSb and InAs assuming KANE'S band structure. However, as BOWERS and YAFET have shown, in order to obtain a satisfactory quantative agreement with experiment the spin‐orbit interaction as well as the interaction with higher bands, must be taken into account. It is suggested that the threefold reversal of sign of the susceptibility as observed experimentally by GEIST in InAs, may be due to the g ‐factor vanishing at the Fermi energy corresponding to an electron concentration of 5 × 10 19 cm −3 .