Strain/defect induced enhanced coercivity in single domain CoFe2O4 nanoparticles

• Synthesized single domain CoFe2O4 nanoparticles of similar sizes but with different amount of defects and strain by controlling the growth conditions in the hydrothermal method.
• Demonstrated that the presence of strain in the CoFe2O4 nanoparticles plays a important role in controlling their magnetic properties.
• M-H characteristics of CoFe2O4 nanoparticles were simulated using Object Oriented MicroMagetic Framework for the intrinsic strain.
• CoFe2O4 nanoparticles with higher value of intrinsic strain exhibits larger coercivity and is correlated to the strain induced enhanced anisotropy.

Two sets of single domain CoFe2O4 (CFO) nanoparticles have been synthesized using hydrothermal technique which are of the same sizes, but with different amount of strain/defects. The nanoparticles synthesized at a lower growth temperature (80 °C) exhibit high density of planar defects and oxygen vacancies as compared to the CFO nanoparticles grown at higher temperature (180 °C). The CFO nanoparticles with high density of defects also possess higher intrinsic strain. The nanoparticles with higher strain/defects exhibit higher coercivity and smaller value of saturation magnetization. The effect of strain on the magnetization characteristics of CFO nanoparticles is simulated using the Object Oriented MicroMagnetic Framework. The observed larger value of coercivity for the CFO nanoparticles with higher intrinsic strain is attributed to strain induced enhanced anisotropy of the nanoparticles.