  Materials which possess coupling between different degrees of freedom such as
charge, spin, orbital and lattice are of tremendous interest due to their
potential for device applications. It has been recently realized that some of
manganite perovskite oxides show structural and ferroelectric instabilities
which may be tuned by imposing internal or external strain. Among manganite
perovskites, AMnO3 (A = Ca, Sr and Ba) are reported to be good candidates to
show spin-phonon coupling driven multiferroicity. Here, we have probed the
correlation between vibrational and magnetic properties in the 9R-type
hexagonal Ba0.9Sr0.1MnO3 (BSM10). Nine Raman active modes are observed which
are characteristic phonon modes for 9R phase. The frequency ({omega}) of an Eg
(344 cm-1) mode which is related to Mn vibrations shows anomaly with
temperature (T) manifested as a change in slope of {omega} vs T at 260 K. The
temperature-dependent magnetization of BSM10 suggests a possible
antiferromagnetic ordering at ~ 260 K. We, therefore, attribute the phonon
anomaly to spin-phonon coupling arising due to the magnetic ordering.
