The spin-chain systems are interesting for various fascinating phenomena such as geometrical frustration, single-ion-magnetism, spin-gap, etc. Recently, it is observed that spin-chain can also favor magnetoelectric (ME) coupling, though, the mechanism is not clearly understood. The spin-chain oxide Sr2Ca2CoMn2O9 exhibits long-range magnetic ordering and strong ME coupling. However, the compound Sr4CoMn2O9 (where Ca is fully replaced by Sr) exhibits single ion magnetism (SIM) without LRO, though ME coupling is still present. This is rare in literature. The proposed µSR investigation (2-50 K) in zero-field and longitudinal field of 40 kOe will enable us to understand the nature of magnetic ground state and detail spin dynamics; which in turns will help to understand the mechanism of ME coupling and the significant role of non-magnetic ions (i.e. Sr/Ca concentration) on complex magnetism