Magnetic Susceptibility of Germanium

Abstract

The magnetic susceptibility of a variety of Ge specimens has been measured as a function of temperature over the range from 70 to 300°K. The susceptibility of high-purity specimens shows an unexpected temperature dependence: a decreasing diamagnetism with increasing temperature. By subtracting the susceptibility of high-purity Ge at each temperature from that of impure material, the charge carrier susceptibility has been obtained for a number of $n$- and $p$-type specimens. The effective mass of electrons obtained from susceptibility measurements on $n$-type Ge is in agreement with values yielded by cyclotron resonance. Analysis of the range of transition from classical to Fermi-Dirac statistics suggests that the energy surfaces of the conduction band can be described by four rather than eight ellipsoids of revolution in $k$-space. In $p$-type Ge the agreement with cyclotron resonance results is not nearly so good in that a larger hole effective mass is required by the susceptibility data. Measurements have been made on one $n$-type specimen bombarded with fast neutrons. After exposures sufficient to produce essentially intrinsic behavior, there was no trace of the paramagnetic component expected from unpaired spins of trapped electrons. This result has been interpreted as indicating that the energy levels associated with bombardment-produced defects form overlapping, degenerate impurity bands for the exposure in question.