Understanding the role of iron in the magnetism of Fe doped ZnO nanoparticles

Abstract

The actual role of transition metals like iron in the room temperature ferromagnetism (RTFM) of Fe doped ZnO nanoparticles is still an unsolved problem. While some studies concluded that the Fe ions participate in the magnetic interaction, others in contrast do not believe Fe to play a direct role in the magnetic exchange interaction. To contribute to the understanding of this issue, we have carefully investigated the structural, optical, vibrational and magnetic properties of sol-gel synthesized Zn1-xFexO (0 < x < 0.10) nanoparticles. No Fe(2+) was detected in any sample. We found that high spin Fe(3+) ions are substitutionally incorporated at the Zn(2+) in the tetrahedral-core sites and in pseudo-octahedral surface sites in ZnO. Superficial OH(-) was observed in all samples. For x ≤ 0.03, an increment in Fe doping concentration decreased a and c lattice parameters, average Zn-O bond length, average crystallite size and band gap; while it increased the degree of distortion and quadrupole splitting. Undoped ZnO nanoparticles exhibited very weak RTFM with a saturation magnetization (Ms) of ∼0.47 memu g(-1) and this value increased to ∼2.1 memu g(-1) for Zn0.99Fe0.01O. Very interestingly, the Ms for Zn0.99Fe0.01O and Zn0.97Fe0.03O increased by a factor of about ∼2.3 by increasing annealing for 1 h to 3 h. For x ≥ 0.05, ferrimagnetic disordered spinel ZnFe2O4 was formed and this phase was found to become more ordered with increasing annealing time. Fe does not contribute directly to the RTFM, but its presence promoted the formation of additional single charged oxygen vacancies, zinc vacancies, and more oxygen-ended polar terminations at the nanoparticle surface. These defects, which are mainly superficial, altered the electronic structure and are considered as the main sources of the observed ferromagnetism.

Disinfection of Multidrug Resistant Escherichia coli by Solar-Photocatalysis using Fe-doped ZnO Nanoparticles

“…The lattice parameters of Fe/ZnO and ZnO NPs were calculated from the XRD and were found to be; a = b = 3.246 Å, c = 5.2053 Å and a = b = 3.248 Å, c = 5.2058 Å, respectively. Lattice parameters of Fe/ZnO were slightly less than those of ZnO, suggesting that the Fe 3+ ions were doped into the ZnO crystal lattice without changing the wurtzite structure 30 .

Figure 1( a ) XRD pattern, ( b ) FTIR spectrum, and ( c ) photoluminescence spectrum of Fe/ZnO NPs.

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Composition‐Dependent Microstructures and Properties of La‐, Zn‐, and Cr‐Modified 0.675BiFeO3–0.325BaTiO3 Ceramics

“…First, room‐temperature switchable magnetization in BF–BT:Zn is predominantly attributed to the isolated ZnO particles. Some of the Zn cations have entered into lattice to substitute B‐site Fe/Ti cations, therefore, some substituted Fe/Ti cations enter into the ZnO to form diluted magnetic materials of ZnO:Fe and/or ZnO:Ti, both show room‐temperature ferromagnetic behavior . Second, the origin for room‐temperature switchable magnetization of BF–BT:Cr includes the two factors.…”

“…It is noted that doping a low amount of oxide can not only promote the sintering of perovskite oxides and enhance their resistivity, 37 but also lead to different chemical clusters and point defects, which have positive effects on room-temperature magnetic property. [38][39][40][41] More interestingly, such a low amount of doping can tune ferroelectric property without detrimental effects on ferroelectric T c . 37,42 Accordingly, doping appropriate chemical oxides might be an effective way to achieve switchable polarization and magnetization of BiFeO 3 -BaTiO 3 .…”

Electrical and magnetic phase transition studies of Fe and Mn co-doped BaTiO 3

“…Such trend excludes the possible spin glass behavior in the material[41]. The possible AFM ordering in an otherwise diamagnetic host depend on several factors like site occupancy, optimal doping concentration and suitable annealing time[42]. It is seen fromFig.…”