Micromagnetic analysis of crystallographic texturing and substrate-induced strain effects in NiFe2O4 and CoFe2O4 thin films

Abstract A three-dimensional continuum based micromagnetic model is developed to simulate the magnetization process in polycrystalline thin films and address the influence of crystallographic texturing, grain size and the substrate-induced strain on the spontaneous domain structure and hysteresis curves of NiFe2O4 and CoFe2O4 thin films. The model employs the Landau–Lifshitz–Gilbert equation along with mechanical equilibrium and Gauss' Law for magnetism to calculate the temporal and spatial distributions of the magnetic moments. Thus, this approach falls within the category of phase-field methods used for non-conserved systems. The finite element method is used to solve the partial differential equations in fully coupled fashion while using a different discretization method for each equation. The results demonstrate how the magnetization process is altered by adopting different microstructural orientations revealing stronger sensitivity in CoFe2O4 thin films than in NiFe2O4 thin films. Moreover, it is shown that the substrate-induced compressive strain favors in-plane magnetization, whereas the tensile strain switches the easy axis from the in-plane to the out-of-plane direction. The validity of the model is verified by comparing the results with recently published experimental data for sol-gel deposited NiFe2O4 thin films.