  We propose a new approximation scheme within equation of motion approach
(EOM) to spin polarized transport through a quantum dot coupled to
ferromagnetic leads. It has some advantages over a widely used in the
literature standard EOM technique, in particular when we are interested in spin
polarized quantities. Namely, it gives the values of the dot spin polarization
which are closer to the ones obtained within numerical renormalization group
(NRG), than the standard EOM approach. While restoring the Kondo effect, the
spin polarization vanishes and the transport becomes unpolarized, in agreement
with NRG and a real time diagrammatic calculations. The standard EOM procedure
gives nonzero values of the spin polarization, and the transport is still spin
polarized. Both approximations give the same correct splitting of the Kondo
peaks due to ferromagnetism in the electrodes.

Mesoscale and Nanoscale Physics