  We investigate the noise in spin transport through a single quantum dot (QD)
tunnel coupled to ferromagnetic electrodes with noncollinear magnetizations.
Based on a spin-resolved quantum master equation, auto- and cross-correlations
of spin-resolved currents are analyzed to reveal the underlying spin transport
dynamics and characteristics for various polarizations. We find the currents of
majority and minority spins could be strongly autocorrelated despite
uncorrelated charge transfer. The interplay between tunnel coupling and the
Coulomb interaction gives rise to an exchange magnetic field, leading to the
precession of the accumulated spin in the QD. It strongly suppresses the
bunching of spin tunneling events and results in a unique double-peak structure
in the noise of the net spin current. The spin autocorrelation is found to be
susceptible to magnetization alignments, which may serve as a sensitive tool to
measure the magnetization directions between the ferromagnetic electrodes.
