Composition-Driven Surface Reorganization and Fractal Scaling in PCL/BaMTi4+ Polymer–Ferrite Composite Films

Flexible polymer–ferrite composites provide a route for lightweight functional materials with tunable surface and structural properties. Here, poly(ε-caprolactone) (PCL)/Ti4+-doped barium hexaferrite (BaMTi4+) films containing 10–50 wt.% ferrite were prepared by solvent casting and characterized by XRD, FTIR, SEM, AFM, and fractal analysis. XRD confirmed the coexistence of semicrystalline PCL and magnetoplumbite-type BaMTi4+, whereas FTIR indicated preservation of the polymer backbone and non-covalent interfacial interactions. Morphological and topographical analyses revealed a composition-dependent transition from compact polymer-rich surfaces to rougher ferrite-rich architectures. Surface roughness decreased at 10 wt.% BaMTi4+ and increased at higher loadings, reaching Sa = 33.10 nm and Sq = 42.54 nm at 50 wt.%. Power spectral density and fractal analyses showed enhanced spatial correlation, with the Hurst exponent increasing from 0.51 to 0.81 and the fractal dimension decreasing from 2.49 to 2.19. These results demonstrate that ferrite loading effectively controls the multiscale surface organization of magnetically active PCL films.