Graphene nanoplatelets/Li-Mg-Sm spinel ferrite nanocomposites with improved dielectric and magnetic properties

•SGAC route was employed to prepare Li0.2Mg0.6Sm0.03Fe2.17O4/Graphene nanoplatelets composites.•The crystallite size was minimum for GNPs concentration 5 wt%GNPs.•Raman modes also confirmed the existence of GNPs in the LMSF lattice.•The ε′ and tanδ was reduced with increasing frequency.•The MS was also reduced with the substitution of non-magnetic GNPs.•The as-prepared LMSF/GNPs composites are useful for high frequency and recording and storing media devices.