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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