  Frequency dependent current noise in ferromagnetic double junctions with
Coulomb blockade is studied theoretically in the limit of sequential tunneling.
Two different relaxation processes are found in the correlations between spin
polarized tunneling currents; low frequency spin fluctuations and high
frequency charge fluctuations. Spin accumulation in strongly asymmetric
junctions is shown to lead to a negative differential resistance. We also show
that large spin noise activated in the range of negative differential
resistance gives rise to a significant enhancement of the current noise.
