Structural and magnetic properties of sol–gel derived NiFe2O4 thin films on silicon substrates

Spinel NiFe2O4 thin films are derived via chemical solution deposition on silicon substrates. The films show a granular microstructure with surface roughness of less than 3 nm. The effects of varying the pyrolysis and annealing conditions on the microstructure and resulting magnetic properties have been studied. Microstructural studies confirm the formation of randomly oriented, phase-pure spinel nickel ferrite for pyrolysis at 100 °C to 500 °C and crystallization at 650 °C to 900 °C for 10 to 30 min. It is shown that the pyrolysis temperature does not affect the microstructure and the resulting magnetic properties, while increasing annealing temperature results in increased grain size and saturation magnetization. Transmission electron microcopy shows that no intermediate or secondary phase has formed at the interface even at annealing temperature as high as 900 °C. - Highlights: • Nanocrystalline NiFe2O4 thin films are derived by a chemical solution deposition. • The pyrolysis temperature has no effect on microstructure and magnetic properties. • Increase in annealing temperature results in larger grain size. • Higher annealing temperature leads to higher saturation magnetization. • TEM confirms purity of the films even at annealing temperature as high as 900 °C