Electron interaction effect on the spin diffusion and transport in half metallic magnets

For half metallic magnets, spin fluctuation is the same as charge fluctuation. The length scale is controlled by electron-electron interaction and is of the order of the screening length, typically of the order of an Angstrom whereas the ordinary spin diffusion length is of the order of 100 Å or more. We examine the eigenstates for charge and spin transport for systems close to half-metallicity. Due to the electron-electron interaction, the decay length of the eigenstate that corresponds to the longitudinal spin diffusion length is much reduced, consistent with recent experimental results. We explore the consequence of this. We find that there are two parameters that characterize half-metallicity and illustrate our results numerically with a simple model.