  Superconductor/ferromagnet/superconductor Josephson junctions are
paradigmatic systems for studying the delicate interplay of superconductivity
and magnetism via proximity effects as well as their composite excitations.
Here, we analyse the collective modes (CM) in such a heterostructure by taking
into account the interplay between the de-magnetisation field $H_{dem}$ and the
field caused by the anisotropy of the ferromagnet $H_{an}$, which was
previously neglected. It turns out that the spectrum of composite collective
modes, $\omega(k)$, has a qualitatively different form in the case of
$H_{dem}<H_{an}$ and of $H_{dem}>H_{an}$. In the first case, the dependence
$\omega(k)$ has the same form as in previous studies, whereas in the second
case, the spectrum looks completely different. In particular, for moderate or
weak anisotropy in ferromagnet the group velocity of collective modes
demonstrates inflection point where the group velocity become infinite and is
superluminal. Furthermore, this point separates purely real and
complex-conjugate solutions for the collective modes and is also {\it exception
point}. We show that the difference of the CMs spectra can be revealed by Fiske
experiment, i.\,e.\,by measuring the $I-V$ characteristics in the presence of
magnetic field and voltage.
