Paramagnetic Susceptibility of Metallic Lithium and Sodium by Electron Spin Resonance Saturation

Abstract

The total conduction electron spin moment of lithium and sodium dispersions has been measured in polarizing fields of about 10 G. The steady-state change in sample polarization at electron spin resonance was detected and then extrapolated to the limit of full saturation. Surprisingly, it was found that because the rf fields were linearly polarized and comparable to the polarizing field, the saturation level did not increase monotonically with rf field strength. The data were in good fit with saturation curves derived by means of numerical integration of the modified Bloch equation. The conduction electron spin susceptibility ${\chi }_s$ for lithium at 300°K was (1.96±0.10)×${10}^{-6\mathrm{}}$ cgs volume units. The relative values of ${\chi }_s$ in lithium were the same at 300, 77, and 1.5°K, within an estimated uncertainty of 3%, and the relative values of ${\chi }_s$ in sodium were the same at 77 and 1.5°K, within an estimated uncertainty of 5%.