Ferromagnetic Behaviors in Fe‐Doped NiO Nanofibers Synthesized by Electrospinning Method

Abstract

Ni1−xFexOnanofibers with different Fe doping concentration have been synthesized by electrospinning method. An analysis of the phase composition and microstructure shows that Fe doping has no influence on the crystal structure and morphology of NiO nanofibers, which reveals that the doped Fe ions have been incorporated into the NiO host lattice. Pure NiO without Fe doping is antiferromagnetic, yet all the Fe-doped NiO nanofiber samples show obvious room-temperature ferromagnetic properties. The saturation magnetization of the nanofibers can be enhanced with increasing Fe doping concentration, which can be ascribed to the double exchange mechanism through the doped Fe ions and free charge carriers. In addition, it was found that the diameter of nanofibers has significant impact on the ferromagnetic properties, which was discussed in detail.

Understanding the Magnetic Memory Effect in Fe-Doped NiO Nanoparticles for the Development of Spintronic Devices

“…Therefore, a question remains unanswered: what could be the possible mechanism for RT FM properties from TM-doped TMOs? To answer this question, we summarize the grain size ( d ) dependency of the reported RT magnetic properties from Ni 1– x M x O (M = Cr, Mn, ,,, Fe, ,,,− , Co, ,, Cu, Zn, , Sn, and Ce) and Ni 1– x Fe x O in Figures a and b, respectively, where the vertical axis represents the concentration x of the dopant. Here different colors are used to represent the grain-size-dependent magnetic properties of undoped NiO NPs as discussed in the Introduction, which can be split into three regions (Re), namely Re-I ( d ≤ 10 nm) SPM/SG/SSG, Re-II (10 nm ≤ d ≤ 30 nm) FM, and Re-III ( d ≥ 30 nm) AF (no finite size effect induced magnetism), respectively from left to right.…”

“…Interestingly, nonstoichiometric properties in NiO can be enhanced further by doping with TMs such as Cr, Mn, − Fe, ,− Co, ,, Cu, and Zn, , which mostly depend on the method of sample preparation, and experimental variables such as thermal treatment (i.e., grain size), oxygen activity, and the fraction of dopant . The above-mentioned factors affect the magnetic, structural, and electronic properties which are of great importance for the basic understanding of TMO-DMSs.…”