Sol–gel auto-combustion synthesis of PVP/CoFe2O4 nanocomposite and its magnetic characterization

• The Poly(vinyl pyrrolidone) (PVP) was used as a surface capping agent.
• PVP/CoFe2O4 nanocomposite was synthesized by a sol-gel auto-combustion method.
• The existence of the spin-disordered surface layer was established.

Poly(vinyl pyrrolidone)/CoFe2O4 nanocomposite has been fabricated by a sol–gel auto-combustion method. Poly(vinyl pyrrolidone) was used as a reducing agent as well as a surface capping agent to prevent particle aggregation and stabilize the particles. The average crystallite size estimated from X-ray line profile fitting was found to be 20 ± 7 nm. The high field irreversibility and unsaturated magnetization behaviours indicate the presence of the core–shell structure in the sample. The exchange bias effect observed at 10 K suggests the existence of the magnetically aligned core surrounded by spin-disordered surface layer. The reduced remanent magnetization value of 0.6 at 10 K (higher than the theoretical value of 0.5) shows the PVP/CoFe2O4 nanocomposite to have cubic magnetocrystalline anisotropy according to the Stoner–Wohlfarth model.

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