Coexistence of ferri and ferromagnetism in cobalt substituted samarium iron garnet

[Display omitted] •The effect of Co substitution on structural, morphological, chemical and magnetic properties of Sm3Fe5O12 is studied.•The effect of Co substitution on the Sm3Fe5O12 crystal structure, especially on the Fe(a)-O-Fe(d) bond has been done by performing Rietveld refinement on the respective XRD data.•Modification in the particle morphology and chemical properties of Sm3Fe5-xCoxO12 were studied using SEM images and XPS analysis respectively.•Co substitution noticeably enhance the magnetic properties including (MS), (MR) and (HC) in Sm3Fe5-xCoxO12. Samarium iron garnet (Sm3Fe5O12) is a potential but less explored ferromagnetic rare earth iron garnet. Cobalt substitution induced structural modifications that results enhancement in room temperature as well as low temperature magnetic behavior of Sm3Fe5O12 prepared by co-precipitation has been probed using superconducting quantum interface device. At room temperature, replacement of 0.3 atomic% Fe by Co improves the saturation value from 12.63 to 25.26 emu/g and the coercivity is found to be increased from 0.023 to 0.09 kOe. Similarly, at low temperature (∼5K) the enhancement in saturation magnetization and coercivity is found to be 17.62 to 31.23 emu/g and 1.55 to 2.32 kOe respectively. Rooted from the morphological modifications, the enhanced magnetism observed here might also be from the modifications in the super-exchange interaction and formation of oxygen vacancies due to the larger ionic radius of replaced Co2+ ions in the Fe3+ sites of Sm3Fe5O12.