Co_1-xZn_xFe₂O₄ nanofiber：Synthesized by electrospinning and its magnetic properties

Well-aligned and uniform Co_0.8Zn_0.2Fe₂O₄ nanofibers (NFs) are prepared by electrospinning via sol–gel and subsequent heat treatment. Each of the as-spun NFs has a diameter of about 300 nm and a smooth surface morphology. The scanning electron microscope (SEM) image shows that the diameter decreases to 70 nm after the Co_0.8Zn_0.2Fe₂O₄ NF has been annealed at 650 ℃ for 3 h. The structure and chemical of Co_0.8Zn_0.2Fe₂O₄ NF are investigated by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS), respectively. Single phase cubic spinel structure, Co_0.8Zn_0.2Fe₂O₄ NF, is successfully obtained after having been calcined at 550 ℃ in air for 3 h, and a reduced lattice constant of the Co_0.8Zn_0.2Fe₂O₄ NF provides the evidence of effective Zn²⁺ substitution. The magnetic measurements show that the substitution of Zn²⁺ for Co²⁺, i.e., the introduction of non-magnetic Zn²⁺ ions into A sites, can increase the saturation magnetization (M_s) and reduce the coercivity (H_c). The obtained H_c results of different samples reveal that the critical single-domain size of the Co_0.8Zn_0.2Fe₂O₄ NF is approximately 44 nm. By doping Zn²⁺ with different concentrations, the morphologies of Co_1-xZn_xFe₂O₄ (0≤ x ≤ 0.5) NFs do not show obvious changes. For magnetic properties, the M_s increases and H_c decreases monotonically, respectively.