  A general definition of the Spintronics concept of spin-pumping is proposed
as generalized forces conjugated to the spin degrees of freedom in the
framework of the theory of mesoscopic non-equilibrium thermodynamics. It is
shown that at least three different kinds of spin-pumping forces and associated
spin-currents can be defined in the most simple spintronics system (the
Ferromagnetic/Non-Ferromagnetic metal interface). Furthermore, the generalized
force associated to the ferromagnetic collective variable is also introduced in
an equal footing, in order to describe the coexistence of the spin of the
conduction electrons (paramagnetic spins attached to $s$-band electrons) and
the ferromagnetic-order parameter. The dynamical coupling between these two
kinds of magnetic degrees of freedom is presented, and interpreted in terms of
spin-transfer effects.

Mesoscale and Nanoscale Physics