Optical band gap hierarchy in a magnetic oxide: Electronic structure of NiFe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>

Sun, Qi; Sims, Hunter; Mazumdar, Dipanjan; X., J.; Holinsworth, B. S.; O’Neal, Kenneth; Kim, G.; Butler, W. H.; Gupta, Arunava; Musfeldt, J. L.

doi:10.1103/physrevb.86.205106

Cited by 93 publications

(51 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is worth mentioning that in order to extract the band gap energies the curves are shifted such that the plateau regions are at zero absorption. For the NFO the optical band gap is estimated to be E NFO gap ≈ 1.49 eV, close to previous publications [20,39]. The optical band gap for the NiFe 2 O x1 and NiFe 2 O x2 samples is E NiFe2Ox 1 gap ≈ 1.27 eV and E NiFe2Ox 2 gap ≈ 1.09 eV, respectively, unveiling the more conducting character of the latter.…”

Section: Experimental Techniquessupporting

confidence: 87%

Electrical transport and optical band gap of NiFe2Ox thin films

Bougiatioti

Manos

Klewe

et al. 2017

Journal of Applied Physics

View full text Add to dashboard Cite

We fabricated NiFe2Ox thin films on MgAl2O4(001) substrates by reactive dc magnetron cosputtering varying the oxygen partial pressure during deposition. The fabrication of a variable material with oxygen deficiency leads to controllable electrical and optical properties which would be beneficial for the investigations of the transport phenomena and would, therefore, promote the use of such materials in spintronic and spin caloritronic applications. We used several characterization techniques in order to investigate the film properties, focusing on their structural, magnetic, electrical, and optical properties. From the electrical resistivity measurements we obtained the conduction mechanisms that govern the systems in high and low temperature regimes, extracting low thermal activation energies which unveil extrinsic transport mechanisms. The thermal activation energy decreases in the less oxidized samples revealing the pronounced contribution of a large amount of electronic states localized in the band gap to the electrical conductivity. Hall effect measurements showed the mixed-type semiconducting character of our films. The optical band gaps were determined via ultraviolet-visible spectroscopy. They follow a similar trend as the thermal activation energy, with lower band gap values in the less oxidized samples.

show abstract

Section: Experimental Techniquessupporting

confidence: 87%

Electrical transport and optical band gap of NiFe2Ox thin films

Bougiatioti

Manos

Klewe

et al. 2017

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…The effective U (i.e. U -J = 3 eV) is applied to Ni-d, Fe-d and Yb-f orbitals and the calculations are carried out using rotationally invariant Dudarev approach [33] The electronic structure of pure NFO has been investigated by many in the past in the context of strong correlation effect [32,34], spin-filter efficiency [3] and stability of normal and inverse spinel configuration [17,30,31]. In the present study, the electronic structure of NFO is revisited in order to examine the effect of substitution of Yb as well as to explain the insulating mechanism of the parent compound.…”

Section: A Computational Detailsmentioning

confidence: 99%

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

et al. 2017

View full text Add to dashboard Cite

Spin-polarized density functional calculations, magnetization, and neutron diffraction (ND) measurements are carried out to investigate the magnetic exchange interactions and strong correlation effects in Yb substituted inverse spinel nickel ferrite. In the pristine form, the compound is found to be a mixed insulator under the Zaanen-Sawatzky-Allen classification scheme as it features both charge transfer and Mott insulator mechanism. Estimation of magnetic exchange couplings reveals that both octahedral-octahedral and octahedral-tetrahedral spin-spin interactions are antiferromagnetic. This is typical of spin-frustrated triangular lattice with one of the vertices occupied by tetrahedral spins and remaining two are occupied by octahedral spins. However, since the octahedral-tetrahedral interaction is dominant, it leads to a forced parallel alignment of the spins at the octahedral site which is in agreement with the results of ND measurements. The substituent Yb is found to be settled in +3 charge state, as confirmed from the XPS measurements, to behave like a spin-half impurity carried by the localized f z(x 2 −y 2 ) orbital. The impurity f spin significantly weakens the antiferromagnetic coupling with the spins at the tetrahedral site, which explains the experimental observation of fall in Curie temperature with Yb substitution.

show abstract

“…4 depicts the optical absorption spectrum of an NFO film in an energy range from 0.8 eV to 5.6 eV. Experimental data by Holinsworth et al 28,29 and a calculated spectrum by Meinert et al 30 are shown for comparison. The absorption coefficient α(E) was obtained from the measured transmission and reflectance spectra by α = .…”

Section: Electronic Propertiesmentioning

confidence: 99%

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

Self Cite

View full text Add to dashboard Cite

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+ .

show abstract

Optical band gap hierarchy in a magnetic oxide: Electronic structure of NiFe2O4

Cited by 93 publications

References 39 publications

Electrical transport and optical band gap of NiFe2Ox thin films

Electrical transport and optical band gap of NiFe2Ox thin films

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

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

Contact Info

Product

Resources

About