  Detection of current-induced spin accumulation via ferromagnetic contacts is
discussed. Onsager's relations forbid that in a two-probe configuration spins
excited by currents in time-reversal symmetric systems can be detected by
switching the magnetization of a ferromangetic detector contact. Nevertheless,
current-induced spins can be transferred as a torque to a contact magnetization
and affect the charge currents in many-terminal configurations. We demonstrate
the general concepts by solving the microscopic transport equations for the
diffuse Rashba system with magnetic contacts.
