Magnetization in Phosphorus Doped Silicon

Magnetization in phosphorus doped silicon was measured with magnetic fields up to 95 kG and temperatures down to 1.5 K. The donor concentration of measured samples ranged from 0.53 to 6.5 times 10 18 cm -3 . The most heavily doped sample shows diamagnetic susceptibility which is consistent with a simplified picture of degenerate semiconductor. Other samples, including two metallic ones, show a temperature dependence of magnetization which can be attributed to free spins, and the number densities of free spins estimated from the magnetization curve are shown consistent with those estimated from the specific heat anomaly. The origin of these free spins is discussed with taking into account the intrastate Coulomb energy of localized states.