Magnetization noise in magnetoelectronic nanostructures
  By scattering theory we show that spin current noise in normal electric conductors in contact with nanoscale ferromagnets increases the magnetization noise by means of a fluctuating spin-transfer torque. Johnson-Nyquist noise in the spin current is related to the increased Gilbert damping due to spin pumping, in accordance with the fluctuation-dissipation theorem. Spin current shot noise in the presence of an applied bias is the dominant contribution to the magnetization noise at low temperatures. 
Jorn Foros, Arne Brataas, Yaroslav Tserkovnyak and Gerrit E. W. Bauer