By depositing a high-density ferromagnetic cobalt ferrite (CFO) layer in the rod gaps in c-axis-oriented epitaxial Bi3.9Nd0.3Eu0.1Ti3O12.5 (BNEuT) films with a microrod morphology by metal organic decomposition (MOD), microrod-type multiferroic CFO/BNEuT composite thin films were fabricated. The effects of the soaking time during the annealing treatment on the structural, magnetic, and ferroelectric characteristics of the resulting composite films were investigated. The MOD-deposited and annealed films contained single-phase CFO with a cubic inverse-spinel structure. The Fe/Co ratio for the annealed samples gradually increased with increasing soaking time from 3 to 10 h, because of the transfer of Co atoms from the bottom layer during high-temperature aging. The CFO/BNEuT composite films annealed at 700 °C for 1–10 h exhibited magnetic shape anisotropy, and annealing under a nitrogen atmosphere was effective for improving the magnetic properties. Little soaking time dependence was found for the remanent polarization, which was almost constant at 1.0–1.5 μC cm−2.

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Microrod-type CoFe2O4(CFO)/Bi3.25Nd0.65Eu0.10Ti3O12(00ℓ) (BNEuT) composite thin films were fabricated by a combination of high-temperature sputtering, reactive ion etching, and metal organic chemical vapor deposition (MOCVD) on Pt(100)/MgO(100) substrates. The substrate temperature for MOCVD was varied from 450 °C to 600 °C to examine its effect on the structural, magnetic, and ferroelectric properties. The substrate temperature affects the compressive stress at the interface between the CFO and BNEuT. The surface morphology changed drastically above 550 °C. The room temperature magnetization–magnetic field hysteresis loops for the films showed clear ferromagnetic hysteresis loop and magnetic shape anisotropy. The room temperature polarization–electric field (P−E) hysteresis loops for the films showed a clear ferroelectric hysteresis loop, and slightly leaky P−E hysteresis loop. The coercive field increased slightly with increasing substrate temperature. Judging from the structural, ferromagnetic, and ferroelectric properties, the film deposited at 550 °C has potential as an excellent multiferroic material.