Magnetic Susceptibility of Insulating and Semiconducting Strontium Titanate

The magnetic susceptibility of strontium titanate with and without charge carriers has been measured at 300, 78, and 4.2°K. Insulating SrTi${\mathrm{O}}_3$ shows a magnetic moment, which is partly diamagnetic and partly (Van Vleck) paramagnetic. The free-carrier contribution is mainly paramagnetic because of the high density of states. As the concentration of carriers is increased the temperature dependence disappears. At the highest concentration (∼6×${10}^{20}$/cc), pure Pauli paramagnetism is observed. The density-of-states effective mass at the bottom of the conduction band deduced from these measurements is $5m_0$, in good agreement with values from transport experiments.