Polyvinylpyrrolidone (PVP)/MnFe2O4 nanocomposite: Sol–Gel autocombustion synthesis and its magnetic characterization

A polyvinylpyrrolidone (PVP)/MnFe2O4 nanocomposite was prepared by the sol–gel autocombustion method and its structural, thermal, spectroscoppic, morphological and magnetic characterizations were done by XRD, FT-IR, TGA, SEM and VSM techniques. The presence of MnFe2O4 was confirmed by XRD and the size of crystallites was estimated to be 11±3 nm. Morphology analysis by SEM revealed spherical agglomerates of 15 nm. The magnetization curves confirm a superparamagnetic behavior with a blocking temperature of 287 K. The Mr/Ms value suggests the presence of uniaxial anisotropy in MnFe2O4 nanoparticles, instead of the expected cubic anisotropy according to the Stoner–Wohlfarth model. The effective magnetic anisotropy constant Keff has been determined to be about 1.42×106 erg/cm3 which is significantly higher than that of the bulk MnFe2O4. This suggests a strong magnetic coupling between magnetically ordered core spins and disordered surface spins of the nanoparticles in the nanocomposite.