Synthesis and microwave magnetic properties of magnetite nanowire arrays in polycarbonate templates

Magnetic nanowire arrays have potential applications in magnetic memory, microwave magnetic devices and many other fields. Spinel ferrite nanowire arrays exhibit a higher resistivity compared with metal counterparts; they also possess a strong shape anisotropy, such that they have high feasibility in microwave magnetic devices. Herein crystalline Fe3O4 nanowire arrays were synthesized in polycarbonate porous membranes with pore sizes of 100 nm in diameter by one-step electrochemical deposition without heating. The phase structures, morphologies and magnetic properties were studied by XRD analysis, SEM and TEM observations and microwave magnetic measurements. The results showed that the as-prepared nanowires, characterized by polycrystalline phase structures, were uniform in size, with about 200 nm in diameter and 6-10 µm in length. Microwave magnetic properties of the arrays were characterized from microwave absorption parameters of the flip-chip on a microstrip line using a vector network analyzer (VNA). The ferromagnetic resonance (FMR) frequencies of ferrite arrays reached up to 25 GHz under a magnetic field of 9 kG, and more importantly it could be tuned in a wide frequency range by an external magnetic field. The results indicated that the Fe3O4 nanowire arrays are promising absorbing microwave materials for flexible high-performance microwave devices.