Tuning of crystallographic orientation in CoFe2O4 spinel ferrite thin films at liquid-vapour interface

Abstract

Achieving magnetic anisotropy and directional crystallographic orientation in a magnetic film, typically requires either epitaxial substrates for growth or post-deposition processing, which limits the scalability and transferability of the films. Here, we report an innovative substrate-free, liquid-vapour interfacial method for growing free-standing/floating CoFe2O4 films on the surface of precursor solution under different applied magnetic field orientations. The films grown without magnetic field (CoFe2O4)0 possesses randomly oriented crystallites with low coercivity (Hc = 100.9 Oe), saturation magnetization (Ms = 17.1 emu/cm3), and crystallite size (∼ 17 nm). In contrast, films grown under out-of-plane (CoFe2O4)⊥ and in-plane (CoFe2O4)∥ magnetic fields showed strong preferential (220) orientation with enhanced crystallite sizes of ∼ 19.06 nm and 24.67 nm, respectively. Significantly enhanced Ms = 59.8 emu/cm3, Hc = 910.3 Oe for (CoFe2O4)⊥, and Ms = 118.98 emu/cm3, Hc = 2336.2 Oe for (CoFe2O4)∥ have been obtained. Lotgering orientation factor 0.05, 0.91, and 0.90 for (CoFe2O4)0, (CoFe2O4)⊥ and (CoFe2O4)∥, respectively, shows strong field-induced crystallography alignment in the field-grown films. Angular remanence measurements displayed strong uniaxial anisotropy symmetry aligned with the direction of the applied perpendicular magnetic field, with a residual moment of 1.67 × 10−4 emu, whereas the (CoFe2O4)0 and (CoFe2O4)⊥ films exhibited comparatively weak residual magnetic moments. X-ray photoelectron spectroscopy (XPS) studies shows that the distribution of Co2+ and Fe3+ at octahedral (Oh) and tetrahedral (Td) sites influences the magnetic anisotropy in the films. © 2026 Elsevier B.V.