Laser ablation was used to successfully fabricate multiferroic bilayer thin films, composed of BaTiO₃ (BTO) and CoFe₂O₄ (CFO), on highly doped (100) Si substrates. This study investigates the influence of BaTiO₃ layer thickness (50–220 nm) on the films’ structural, magnetic, and dielectric properties. The dense, polycrystalline films exhibited a tetragonal BaTiO₃ phase and a cubic spinel CoFe₂O₄ layer. Structural analysis revealed compression of the CoFe₂O₄ unit cell along the growth direction, while the BaTiO₃ layer showed a tetragonal distortion, more pronounced in thinner BTO layers. These strain effects, attributed to the mechanical interaction between both layers, induced strain-dependent wasp-waisted behavior in the films’ magnetic hysteresis cycles. The strain effects gradually relaxed with increasing BaTiO₃ thickness. Raman spectroscopy and second harmonic generation studies confirmed BTO’s non-centrosymmetric ferroelectric structure at room temperature. The displayed dielectric permittivity dispersion was modeled using the Havriliak–Negami function combined with a conductivity term. This analysis yielded relaxation times, DC conductivities, and activation energies. The observed BTO relaxation time behavior, indicative of small-polaron transport, changed significantly at the BTO ferroelectric Curie temperature (Tc), presenting activation energies E_τ in the 0.1–0.3 eV range for T < Tc and E_τ > 0.3 eV for T > Tc. The BTO thickness-dependent Tc behavior exhibited critical exponents ν ~ 0.82 consistent with the 3D random Ising universality class, suggesting local disorder and inhomogeneities in the films. This was attributed to the composite structure of BTO grains, comprising an inner bulk-like structure, a gradient strained layer, and a disordered surface layer. DC conductivity analysis indicated that CoFe₂O₄ conduction primarily occurred through hopping in octahedral sites. These findings provide crucial insights into the dynamic dielectric behavior of multiferroic bilayer thin films at the nanoscale, enhancing their potential for application in emerging Si electronics-compatible magneto-electric technologies.

The laser annealing of a Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) thin film on a metglas substrate was simulated in order to understand how the annealing parameters (energy and fluence of the laser, pulse duration, etc) influence the optimization of the crystallinity of the film. Using a 1D heat diffusion equation combined with a finite difference method, the variation of the temperature with the depth relative to the film’s surface and on annealing time was studied. The laser intensity, BCZT’s reflectivity and the temperature dependence of the ther¬mal conductivity and specific heat of the BCZT were considered. No structural phase changes were detected in both the BCZT and the metglas for the values of laser fluence studied, but for 80 mJ/cm2 the maximum temperature approached near the BCZT’s melting temperature. It was observed that since the film’s ther¬mal conductivity decreases with increasing fluence, lower fluences allow for a better distribution of the laser’s energy throughout the crystal lattice, increasing the crystallinity. It was further observed that between consecutive pulses the film’s temperature stabilizes at room temperature.