Design, Controllable Fabrication, and Multifunctional Properties of BiFe _0.9 Cr _0.1 O ₃ Nanotubes and Ni ₈₀ Fe ₂₀ –BiFe _0.9 Cr _0.1 O ₃ Core–Shell Nanowires for Spintronic Applications

A versatile and cost-effective approach was developed to fabricate highly oriented BiFe 0.9 Cr 0.1 O 3 (BFCO) nanotubes and Ni 80 Fe 20 –BiFe 0.9 Cr 0.1 O 3 (NF-BFCO) core–shell nanowires with diameters of approximately 85 nm using a combined sol–gel and electrodeposition process. Uniform and well-aligned antiferromagnetic (AFM) BFCO nanotubes were subsequently filled with a ferromagnetic (FM) NF core to form well-defined FM/AFM interfaces. X-ray diffraction analysis confirmed the rhombohedral perovskite structure (space group R 3 c ) of the BFCO shell, along with the characteristic crystalline peaks of NF. A promising platform for interfacial spin engineering is created by FM/AFM core–shell nanowires. Here, NF-BFCO core–shell nanowires are engineered to take advantage of exchange coupling between an antiferromagnetic oxide shell and a metallic ferromagnetic core, leading to increased exchange bias and coercivity. The temperature dependence of coercivity and magnetization followed the expected 3/2 law and Bloch’s T 3/2 behavior, respectively. Electrochemical tests show that the dense shell structure restricts electrolyte accessibility, resulting in poorer capacitance compared to that of hollow BFCO nanotubes, even though the metallic core enhances electrical transport. These findings demonstrate how multifunctional core–shell designs inherently trade magnetic and electrochemical properties. Overall, the NF-BFCO core–shell nanostructures exhibit multifunctional characteristics, making them promising candidates for magnetic and spintronic device applications.