Electron Spin Paramagnetism of Lithium and Sodium

The paramagnetic susceptibility ${{\chi }_p}^e$ of conduction electron spins is isolated experimentally from the total magnetic susceptibility in metallic lithium and sodium by studying the intensity of the conduction-electron spin resonances. The absolute intensity of absorption is calibrated by comparison with the nuclear resonance of the metal nuclei in the same sample and at the same frequency, the two resonances being observed merely by changing the static magnetic field. In this manner ${{\chi }_p}^e$ is measured in terms of the nuclear static susceptibility, ${{\chi }_p}^n$, which in turn can be calculated accurately from the Langevin-Debye formula. A narrow band modulation technique gives improved signal to noise over our earlier work. The values of ${{\chi }_p}^e$ are (2.08±0.1)×${10}^{-6\mathrm{}}$ cgs volume units for lithium at 300°K and (0.95±0.1)×${10}^{-6\mathrm{}}$ cgs volume units for sodium at 79°K, in rather good agreement with the theory of Pines and Bohm, but in substantial disagreement with the simple Pauli model, or the results of Sampson and Seitz. Experimental precision does not permit conclusions to be drawn about the diamagnetism of conduction electrons.