Zn-ferrite is a versatile material among spinels owing to its physicochemical properties, as demonstrated in rich phase diagrams, with several conductive or magnetic behaviors dictated by its cation inversion. The strength and the type of cation inversion can be manipulated through the various thermal treatment conditions. In this study, inverted Zn-ferrite thin films prepared from radio frequency magnetron sputtering were subjected to different in situ (in vacuum) and ex situ (in air) annealing treatments. The temperature and field dependence of magnetization behaviors reveal multiple magnetic interactions compared to its bulk antiferromagnet behavior. Using the magnetic component model, the different magnetic interactions can be explained in terms of superparamagnetic (SPM), paramagnetic (PM), and ferrimagnetic (FM) contributions. At low temperatures, the SPM and FM contributions can be approximated to the hard and soft ferrimagnetic phases of Zn-ferrite, respectively, which changes with the annealing temperature and sputter power. Distinct magnetic properties emanating from in situ annealing compared to the ex situ annealing were ascribed to the nonzero Fe²⁺/Fe³⁺ ratio, leading to the different magnetic interactions. The anisotropy was found to be the key parameter that governs the behavior of annealed in situ samples.

The quest for improved ferrimagnetic insulators has garnered significant research interest for spintronic devices due to their low damping constants. In this work, we investigated the growth and frequency - dependent microwave properties of sputtered ZnFe ₂ O ₄ thin films grown under different gaseous environments and substrate temperatures ( Ts ). While an argon environment promotes (111) textured ZnFe ₂ O ₄ growth at intermediate Ts , an oxygen environment produces amorphous ZnFe ₂ O ₄ regardless of T_s . A reasonably high effective magnetization, 4π M_eff =~ 0.3-3.7 kG and effective anisotropy were estimated by ferromagnetic resonance (FMR) using Kittel equations in both gaseous environments at intermediate Ts . The lowest Gilbert damping constant (α ≈ 4.18 × 10 ^-3 ) and inhomogeneous broadening (Δ H₀ =318 Oe) were observed at the highest T_S in the argon environment. Landau-Lifshitz damping plus inhomogeneous broadening alone cannot describe the damping in all ZnFe ₂ O ₄ thin films; a low-field-loss effect has to be considered to describe the entire frequency dependence of the linewidth.