  We investigate the linear and nonlinear transport through a single level
quantum dot connected to two ferromagnetic leads in Kondo regime, using the
slave-boson mean field approach for finite on-site Coulomb repulsion. We find
that for antiparallel alignment of the spin orientations in the leads, a single
zero-bias Kondo peak always appears in the voltage-dependent differential
conductance with peak height going down to zero as the polarization grows to
P=1. For parallel configuration, with increasing polarization from zero, the
Kondo peak descends and greatly widens by the appearance of shoulders, and
finally splits into two peaks on both sides of the bias voltage around $P\sim
0.7$ until disappears at even larger polarization strength. At any spin
orientation angle $\theta$, the linear conductance generally drops with growing
polarization strength. For a given finite polarization, the minimum linear
conductance always appears at $\theta=\pi$.
