Current fluctuations in ferromagnetic tunnel junctions

Current shot noise in a double junction consisting of a small metallic grai n connected to two ferromagnetic electrodes is analysed in the limit of seq uential tunneling. We show that, apart from charge fluctuations, there are strong spin fluctuations. We also show that two distinct relaxation process es can be distinguished in the frequency dependent current noise: one in a low frequency range and corresponding to spin fluctuations and another one in a high frequency range corresponding to charge fluctuations.