  The conventional Josephson effect may be modified by introducing spin-active
scattering in the interface-layer of the junction. Here, we discuss a Josephson
junction consisting of two s-wave superconducting leads coupled over a
classical spin that precesses with the Larmor frequency due to an external
magnetic field. This magnetically active interface results in a time-dependent
boundary condition with different tunnelling amplitudes for spin-up and -down
quasiparticles and where the precession produces spin-flip scattering
processes. As a result, the Andreev states develop sidebands and a
non-equilibrium population that depend on the details of the spin precession.
The Andreev states carry a steady-state Josephson charge current and a
time-dependent spin current, whose current-phase relations could be used for
characterising the precessing spin. The spin current is supported by
spin-triplet correlations induced by the spin precession and creates a
feed-back effect on the classical spin in the form of a torque that shifts the
precession frequency.
  By applying a bias voltage, the Josephson frequency adds another complexity
to the situation and may create resonances together with the Larmor frequency.
These Shapiro resonances are manifested as torques and are, under suitable
conditions, able to reverse the direction of the classical spin in
sub-nanosecond time. Another characteristic feature is the subharmonic gap
structure in the dc charge current displaying an even-odd effect that is
attributable to precession-assisted multiple Andreev reflections.
