Effect of Film Thickness on Microstructural and Magnetic Properties of Lithium Ferrite Films Prepared on Strontium Titanate (001) Substrates

Epitaxial lithium ferrite (LiFe5O8) films with different thicknesses were successfully fabricated on strontium titanate (SrTiO3) (001) substrates using the magnetron sputtering deposition technique. The microstructural and magnetic properties of the films were characterized by an advanced transmission electron microscope and a magnetic measurement device. It was found that the formation of structural defects can be influenced by the thickness of the film. In addition to misfit dislocations, orientation domains form in thinner films and twin boundaries appear in thicker films, respectively, contributing to the misfit strain relaxation in the heterosystem. The magnetic measurement showed that the thinner films have enhanced magnetization and a relatively lower coercive field compared with the thicker films containing antiferromagnetic twin boundaries. Our results provide a way of tuning the microstructure and magnetic properties of lithium ferrite films by changing the film thickness.