Computational study of cobalt-modified nickel-ferrite/PZT magnetoelectric composites for voltage tunable inductor applications

Control of magnetic permeability through voltage in magnetoelectric materials promises to create novel voltage tunable inductors. Domain-level phase field modeling and computer simulation are employed to study magnetoelectric composites of Co-modified NiCuZn ferrite and PZT, where ferrite outperforms metallic magnetostrictive materials at high frequencies important for inductor applications. The simulations focus on the interplay between magnetocrystalline anisotropy and stress-induced anisotropy and reveal different regimes of permeability and tunability behaviors. It is shown that the permeability and its tunability can be significantly increased by reducing the intrinsic magnetocrystalline anisotropy through doping NiCuZn-ferrite with Co ²⁺ to form solid solution (1-x)(Ni _0.6 Cu _0.2 Zn _0.2 )Fe ₂ O ₄ -xCoFe ₂ O ₄ , and the optimal performance is achieved at vanishing magnetocrystalline anisotropy constant K ₁ = 0 corresponding to composition x∼0.02. The findings are confirmed by complementary experiments with good agreements. The effect of internal bias stress is further investigated, which is shown to shift the permeability regimes and thus provides an effective engineering technique to optimize the voltage tunable inductor performance. A tunability as high as ∼500% is obtained under the optimal condition, which is much higher than that obtained in conventional high-frequency voltage tunable inductors.