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Using a a-axis-oriented epitaxial (Bi 3.25 Nd 0.65 Eu 0.10 )Ti 3 O 12 (BNEuT) thin films with a microplate-like shape as a ferroelectric pillar material, micropillar-type CoFe 2 O 4 (CFO)/BNEuT(h00)/Nb:TiO 2 (101) composite multiferroic films were fabricated by metal organic chemical vapor deposition. The deposition time was varied from 90-150 min to examine its effect on the structural, ferroelectric, and ferromagnetic characteristics of the films. All the films exhibit single-phase cobalt ferrite with a cubic inverse-spinel structure. The deposited CFO films have a similar columnar structure with a comparatively good step coverage of 37%-66%. The room-temperature magnetization−magnetic field hysteresis loop of the films showed a clear ferromagnetic hysteresis loop, and coercivity decreased from 1.1 to 0.9 kOe with increasing the deposition time. The roomtemperature polarization−electric field hysteresis loop of the films showed a ferroelectric hysteresis loop, and the effect of the leakage current was the smallest for a deposition time of 120 min.

CoFe2O4 (CFO) thin films were deposited on (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT) micropillar films by a non-aqueous sol-gel method. The pitch size of 2–5 μm in the micropillar films used as ferroelectric pillars, and 5 and 15 CFO deposition cycles were examined for high density of CFO nanoparticles. All the CFO films formed by five deposition cycles on BNEuT micropillar films with a pitch size of 2–5 μm were composed of mostly single-phase CFO with a cubic inverse-spinel structure. All the CFO films deposited on the four BNEuT micropillar films were highly dense and had excellent surface flatness, based on surface field-emission scanning electron microscope observations. Based on the structural, magnetic and ferroelectric characteristics, the optimal pitch size for achieving a high density of CFO nanoparticles was 5 μm, and the optimal number of CFO deposition cycles was five.

Highly c-axis oriented (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT) thin films were deposited on the Pt(100)/MgO(100) substrates by high-temperature sputtering. The substrate temperature was varied from 550 °C to 650 °C to examine its effect on the structural, dielectric, ferroelectric, and piezoelectric characteristics of the films, and consequently find the optimal substrate temperature for heteroepitaxial growth of BNEuT thin films. All the films deposited at 580 °C–650 °C exhibited a high degree of c-axis orientation [α(00l)] of ≥97%. All the films grown heteroepitaxially on Pt(100)/MgO(100) substrates was rotated by ±45° with respect to the underlying substrates and had a mainly upward polarization, based on data observed by piezoresponse force microscopy. Judging from the structural, dielectric, ferroelectric, and piezoelectric characteristics, it is shown that the optimal substrate temperature for heteroepitaxial growth of BNEuT films with a high α(00l) of >97% and a comparatively large remanent polarization of 2.0 μC cm−2 is 580 °C.

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.