Charge transfer mediated magnetic response of cobalt ferrite nanoparticles

• π-donor head groups of the surfactant promotes greater ferrimagnetism in CoFe2O4 nanoparticles than σ-donor one.
• Surfactant with larger number of σ-donor head groups activates more ferrimagnetism in CoFe2O4 nanoparticles than the surfactant with smaller number of σ-donor head groups.
• Surfactant having longer chain length enhances the coercivity of CoFe2O4 nanoparticles more than the surfactants with smaller chain length.
• We report a tuned magnetic response of CoFe2O4 nanoparticles depending on the nature of the surface binding ligand.

Herein, we have performed rational surface modification of CoFe2O4 nanoparticles (NPs) to tune its room temperature ferrimagnetic properties by using different non-ionic surfactants. The NPs have been prepared by surfactant-assisted chemical co-precipitation technique with a narrow size distribution. For our study, we have chosen four non-ionic surfactants of triton X and tween group having different chain-lengths. Interestingly, we have found that surfactant co-ordinated magnetic NPs show a maximum of ~94% increase in coercivity along with a considerable decrease in magnetization as compared to the bare one. Systematic investigation reveals that both the nature and number of surfactant׳s head group and chain-length of its alkyl tail group have a remarkable impact on the magnetic properties of CoFe2O4 NPs. We believe that the tuned magnetic response of CoFe2O4 NPs depending on the nature of the surface binding ligand would open up many new opportunities as well as enhance their beneficial activities toward diverse application fields.

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