Influence of oxygen vacancies on the electronic structure and magnetic properties of NiFe2O4 thin films

Jaffari, G. Hassnain; Rumaiz, Abdul K.; Woicik, J. C.; Shah, S. İsmat

doi:10.1063/1.4704690

Cited by 85 publications

(45 citation statements)

References 30 publications

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“…The net magnetization comes from the Ni 2+ (O h ) cations alone,~2µ B , whereas the Fe 3+ moments,~5µ B , in a high spin state for both the O h and T d sites, are antiparallel and cancel each other. This leads to an overall magnetic moment of 2µ B per formula unit (FU) [42]. Density functional theory (DFT) calculations yielded a consistent result for the magnetic moment of nickel ferrite with inverse spinel structure,~2µ B /FU, corresponding to a saturation magnetization, M s , of 50 emu·g −1 [39].…”

Section: Magnetic Measurementsmentioning

confidence: 84%

See 1 more Smart Citation

Development of Novel Magnetoliposomes Containing Nickel Ferrite Nanoparticles Covered with Gold for Applications in Thermotherapy

Rio

Rodrigues

et al. 2020

Materials

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Multifunctional nanosystems combining magnetic and plasmonic properties are a promising approach for cancer therapy, allowing magnetic guidance and a local temperature increase. This capability can provide a triggered drug release and synergistic cytotoxic effect in cancer cells. In this work, nickel ferrite/gold nanoparticles were developed, including nickel ferrite magnetic nanoparticles decorated with plasmonic gold nanoparticles and core/shell nanostructures (with a nickel ferrite core and a gold shell). These nanoparticles were covered with a surfactant/lipid bilayer, originating liposome-like structures with diameters below 160 nm. The heating capacity of these systems, upon excitation with light above 600 nm wavelength, was assessed through the emission quenching of rhodamine B located in the lipid layer. The developed nanosystems show promising results for future applications in thermotherapy.Materials 2020, 13, 815 2 of 19 field, with no remnant magnetization upon magnetic field removal [11][12][13][14]. Generally, nickel ferrite nanoparticles are superparamagnetic when their size is smaller than a critical diameter of around 30 nm [15]. However, nickel-based nanoparticles present some issues such as potential toxicity, high reactivity, and easy degradation, due to the high surface/volume ratio [16]. In order to overcome these problems and make them suitable for biological applications, nickel-containing nanoparticles are usually protected by a suitable coating, such as lipids, polymers, or silica [15,[17][18][19].Combined therapies provide a promising solution for addressing tumor heterogeneity and drug resistance issues, exploring synergistic effects of the different mechanisms of action of multiple therapies, and achieving multiple targets. Hereby, magnetic/plasmonic nanoparticles afford a high therapeutic potentiality owing to the combination of different strategies, such as photothermia, photodynamic therapy, magnetic hyperthermia, and magnetic-guided drug delivery [19]. In this context, iron-oxide magnetic nanoparticles covered with gold or carbon were used [20][21][22]. Recently, manganese ferrite/gold core/shell nanoparticles entrapped in lipid bilayers were also developed as nanocarriers for antitumor drugs [23].Considering these advantages, in this work, both core/shell nickel ferrite/gold nanoparticles and gold-decorated nickel ferrite nanoparticles were prepared. These nanoparticles were covered with a surfactant/lipid bilayer, forming the so-called solid magnetoliposomes. The local heating capacity of these nanosystems was assessed through the inhibition of fluorescence of a fluorophore linked to the lipid layer, when the systems were excited with a light source. The new nanosystems exhibit a strong potential to promote local heating, making them promising for photothermia applications. Materials and MethodsIn all preparations, spectroscopic-grade solvents and ultrapure water of Milli-Q grade (MilliporeSigma, St. Louis, MO, USA) were used. Preparation of Nickel Ferrite/Gold Nanoparticles Pre...

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Section: Magnetic Measurementsmentioning

confidence: 84%

“…The net magnetization comes from the Ni 2+ (Oh) cations alone, ~2μB, whereas the Fe 3+ moments, ~5μB, in a high spin state for both the Oh and Td sites, are antiparallel and cancel each other. This leads to an overall magnetic moment of 2μB per formula unit (FU) [42]…”

Section: Magnetic Measurementsmentioning

confidence: 99%

Development of Novel Magnetoliposomes Containing Nickel Ferrite Nanoparticles Covered with Gold for Applications in Thermotherapy

Rio

Rodrigues

et al. 2020

Materials

View full text Add to dashboard Cite

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“…6 Auger does not overlap with the Fe 2p spectrum and also the characteristic charge transfer feature appears, even though somewhat weaker in intensity compared to that of Fe 2 O 3 . However, the Fe 2p spectrum recorded with the Mg K α source resembles the hard xray PES spectrum of Jaffari et al 44 . Hence, we observe a divalent Ni and a trivalent Fe valence state in this NFO thin film.…”

Section: Cation Distribution and Element Resolved Magnetic Momentsmentioning

confidence: 92%

Physical characteristics and cation distribution of NiFe2O4 thin films with high resistivity prepared by reactive co-sputtering

Klewe¹,

Meinert²,

Boehnke³

et al. 2014

Journal of Applied Physics

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We fabricated NiFe 2 O 4 thin films on MgAl 2 O 4 (001) substrates by reactive dc magnetron co-sputtering in a pure oxygen atmosphere at different substrate temperatures. The film properties were investigated by various techniques with a focus on their structure, surface topography, magnetic characteristics, and transport properties. Structural analysis revealed a good crystallization with epitaxial growth and low roughness and a similar quality as in films grown by pulsed laser deposition. Electrical conductivity measurements showed high room temperature resistivity (12 Ωm), but low activation energy, indicating an extrinsic transport mechanism. A band gap of about 1.55 eV was found by optical spectroscopy. Detailed x-ray spectroscopy studies confirmed the samples to be ferrimagnetic with fully compensated Fe moments. By comparison with multiplet calculations of the spectra we found that the cation valencies are to a large extent Ni 2+ and Fe 3+ .

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“…A number of reasons might be responsible for a strongly increased H c such as exchange coupled grains 51 or a high defect density. 47 On the other hand, similar values for the coercive field measured here have been found on polycrystalline as well as epitaxial Ni x Fe 3−x O 4 thin films.…”

Section: 4951mentioning

confidence: 99%

FromFe3O4/NiO bilayers toNiFe2O4-like thin films through Ni interdiffus

et al. 2016

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Ferrites with (inverse) spinel structure display a large variety of electronic and magnetic properties making some of them interesting for potential applications in spintronics. We investigate the thermally induced interdiffusion of Ni 2+ ions out of NiO into Fe3O4 ultrathin films resulting in off-stoichiometric nickelferrite-like thin layers. We synthesized epitaxial Fe3O4/NiO bilayers on Nb-doped SrTiO3(001) substrates by means of reactive molecular beam epitaxy. Subsequently, we performed an annealing cycle comprising three steps at temperatures of 400• C, 600• C, and 800• C under an oxygen background atmosphere. We studied the changes of the chemical and electronic properties as result of each annealing step with help of hard x-ray photoelectron spectroscopy and found a rather homogenous distribution of Ni and Fe cations throughout the entire film after the overall annealing cycle. For one sample we observed a cationic distribution close to that of the spinel ferrite NiFe2O4. Further evidence comes from low energy electron diffraction patterns indicating a spinel type structure at the surface after annealing. Site and element specific hysteresis loops performed by x-ray magnetic circular dichroism uncovered the antiferrimagnetic alignment between the octahedral coordinated Ni 2+ and Fe 3+ ions and the Fe 3+ in tetrahedral coordination. We find a quite low coercive field of 0.02 T, indicating a rather low defect concentration within the thin ferrite films.

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Influence of oxygen vacancies on the electronic structure and magnetic properties of NiFe2O4 thin films

Cited by 85 publications

References 30 publications

Development of Novel Magnetoliposomes Containing Nickel Ferrite Nanoparticles Covered with Gold for Applications in Thermotherapy

Development of Novel Magnetoliposomes Containing Nickel Ferrite Nanoparticles Covered with Gold for Applications in Thermotherapy

Physical characteristics and cation distribution of NiFe2O4 thin films with high resistivity prepared by reactive co-sputtering

FromFe3O4/NiO bilayers toNiFe2O4-like thin films through Ni interdiffus

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