Bloch Equation for Conduction-Electron Spin Resonance

An effective Bloch equation describing the spin magnetization of the electrons in a metal is derived starting from the usual spin transport equation. No assumption is made as to the direction of the static field, so the effect of the orientation of the field on the diffusion constant is taken into account. The diffusion constant, at resonance, is unchanged when the magnetic field is normal to the surface of the metal, but is altered by a factor ${(1+{{\omega }_c}^2{\tau }^2)}^{-1\mathrm{}}$ for the parallel direction, where ${\omega }_c$ is the cyclotron frequency and $\tau$ the relaxation time. The effect of these results on the transmitted magnetization is discussed.