  We studied Josephson flux-flow (JFF) in Bi-2212 stacks fabricated from single
crystal whiskers by focused ion beam technique. For long junctions with the
in-plane sizes 30 x 2 (mu)m^2, we found considerable contribution of the
in-plane dissipation to the JFF resistivity, (rho)_(Jff), at low temperatures.
According to recent theory [A. Koshelev, Phys. Rev. B62, R3616 (2000)] that
results in quadratic type dependence of (rho)_(Jff)(B) with the following
saturation. The I-V characteristics in JFF regime also can be described
consistently by that theory. In JFF regime we found Shapiro-step response to
the external mm-wave radiation. The step position is proportional to the
frequency of applied microwaves and corresponds to the Josephson emission from
all the 60 intrinsic junctions of the stack being synchronized. That implies
the coherence of the JFF over the whole thickness of the stack and demonstrates
possibility of synchronization of intrinsic junctions by magnetic field. We
also found a threshold character of an appearance of the JFF branch on the I-V
characteristic with the increase of magnetic field, the threshold field B_t
being scaled with the junction size perpendicular to the field L (L = 30-1.4
(mu)m), as B_t = (Phi)_0/Ls, where (Phi)_0 is flux quantum, s is the interlayer
spacing. On the I-V characteristics of small stacks in the JFF regime we found
Fiske-step features associated with resonance of Josephson radiation with the
main resonance cavity mode in transmission line formed by stack.
