  The interplay between different degrees of freedom such as charge, spin,
orbital, and lattice has received a great deal of interest due to its potential
to engineer materials properties and their functionalities for device
applications. In this work, we have explored the crystallographic phase diagram
of Ba1-xSrxMnO3 and studied the correlation between two degrees of freedom,
namely phonons and spins using magnetization and inelastic light scattering
measurements. The system undergoes a series of crystallographic phase
transitions 2H -> 9R -> 4H as a function of doping (Sr) as observed by X-ray
diffraction measurements. Investigation of their temperature-dependent
magnetization reveals a para- to antiferro-magnetic transition for all the
compositions. An Eg phonon in the 9R phase and an E1g phonon in the 4H phase
involving Mn or O-vibrations, show anomalous temperature-dependence in the
antiferromagnetic phase arising due to spin-phonon coupling.
