Facile synthesis of PVA–MnFe2O4 nanocomposite: Its magnetic investigation

Manganese ferrite (MnFe2O4)–polyvinyl alcohol (PVA) nanocomposite was prepared by a PVA assisted sol–gel auto-combustion method. The magnetic core of the carriers was manganese ferrite (MnFe2O4), with average crystallite size of 9.1 ± 2.1 nm. The PVA–MnFe2O4 nanocomposite exhibited superparamagnetic behavior at room temperature and ferromagnetic behavior at low temperatures. Zero-field-cooled and field-cooled measurements further confirm the superparamagnetic behavior with a blocking temperature of 160 K. The lower reduced remanent magnetization values than theoretical value of 0.5 indicate that the PVA/MnFe2O4 nanocomposite used in this study has uniaxial anisotropy rather than the expected cubic anisotropy according to the Stoner–Wohlfarth model. The calculated magnetic anisotropy constant of the sample is ∼1.45 × 106 erg/cm3 which is significantly higher than that of the bulk MnFe2O4 due to the strong magnetic coupling between magnetic core and surface spins.