Tuning of structural, magnetic and optical properties of NiFe2O4films by implementing high magnetic fields

•Floating films of nickel ferrite were formed on the surface of precursor solution.•During the formation of the films, a magnetic field was applied.•Different morphologies of its constituents results due to varying magnetic field.•Properties of the films get influenced by the applied magnetic field. Films of nickel ferrite (NiFe2O4) with tunable geometries possessed by their constituent's viz. nanoparticles, nanopillars, and nanorods have been formed by a one-step film formation method. Floating films were formed on the surface of a precursor solution by exposing the solution to ammonia (NH3) vapor. During the process of film formation, a high magnetic field (˃ 1 Tesla (T)) was applied to influence the formation process and hence the properties of the films. Thus formed films were transferred on glass substrates and annealed at 300 °C. Morphological characterizations demonstrated that depending upon the strength of the applied magnetic field during the formation process, different structures get evolved on the surface of the film. The structures have oriented growth directions of their constituent nano-crystallites. The morphology of the film crystallites and their oriented growth is found to affect the properties of the films. By varying the strength of the applied magnetic field, from 1.25 to 1.75 T, the size of the nano-crystallites is found to vary from 23 to 27 nm. The variations in the crystallite parameters are found to influence the magnetic properties of the films; the optical bandgap is also influenced as it reduced from ~ 4.0 eV to 3.45 eV with the magnetic field.