Reduced Surface Effects and Reduced Inter-particle Interactions in NiFe2O4/TiO2 Nanocomposites.

The magnetic properties of nickel ferrite (NiFe₂O₄) nanoparticles (NPs) and its composite with titanium oxide (TiO₂) have been studied in detail. The average crystallite size was found to be ~ 32 nm for NiFe₂O₄ NPs with and without presence of TiO₂ and confirmed that TiO₂ did not affect the crystalline growth of NiFe₂O₄ NPs. The transmission electron microscopy confirmed the spherical morphology of NPs, whereas the selected area electron diffraction patterns confirmed the polycrystalline nature of these NPs. The zero-field cooled and field cooled magnetization curves confirmed that the blocking temperature lies above the room temperature for both the samples. The gradual increase of magnetization in field cooled curve at low temperatures for NiFe₂O₄/TiO₂ nanocomposites (NCs) indicates the reduced inter-particle magnetic interactions. The value of saturation magnetization was found to be same for both NiFe₂O₄ NPs and NiFe₂O₄/TiO₂ NCs after subtracting the mass contribution of TiO₂ which is non-magnetic in nature. The higher value of fitting parameter B in Bloch's law fit for NiFe₂O₄/TiO₂ NCs indicates the weak exchange coupling constant (J). As the average crystallite size of NiFe₂O₄ NPs is same with and without presence of TiO₂, the lower value of blocking temperature for NiFe₂O₄/TiO₂ NCs indicates the lower value of effective anisotropy constant and reduced surface effects caused by TiO₂. In summary, NiFe₂O₄/TiO₂ NCs showed reduced inter-particle interactions and reduced surface effects. [ABSTRACT FROM AUTHOR]