Electronic structure and optical band gap of CoFe2O4 thin films

Ravindra, A. V.; Padhan, P.; Prellier, W.

doi:10.1063/1.4759001

Cited by 61 publications

(18 citation statements)

References 23 publications

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“…3. Although a strong background signal from STO substrates overwhelms most of the phonon modes161718, the Raman peaks from BFO and CFO can still be clearly detected owing to their smaller band gaps of 2.82 eV1920 and 2.51 eV21, respectively. According to the rhombohedral R 3 c symmetry of BFO, the fingerprint around 162 cm −1 , is assigned as A 1 symmetry mode1922.…”

Section: Resultsmentioning

confidence: 99%

“…According to the rhombohedral R 3 c symmetry of BFO, the fingerprint around 162 cm −1 , is assigned as A 1 symmetry mode1922. The peaks at around 700 cm −1 can then be identified as the A 1g phonon mode of the 192123 cubic spinel CFO. This phonon mode corresponds to the vibration of oxygen towards tetrahedral Fe, which can be utilized to characterize the lattice strains of CFO18192324.…”

Section: Resultsmentioning

confidence: 99%

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Tuning the functionalities of a mesocrystal via structural coupling

Liu

Tsai

et al. 2015

Sci Rep

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In the past decades, mesocrystal, a kind of nanocrystals with specific crystallographic orientation, has drawn a lot of attention due to its intriguing functionalities. While the research community keeps searching for new mesocrystal systems, it is equally crucial to develop new approaches to tune the properties of mesocrystals. In this work, a self-organized two-dimensional mesocrystal composed of highly oriented CoFe2O4 (CFO) nano-crystals with assistance of different perovskite matrices is studied as a model system. We have demonstrated that the strain state and corresponding magnetic properties of the CFO mesocrystal can be modulated by changing the surrounding perovskite matrix through their intimate structural coupling. Interestingly, this controllability is more strongly correlated to the competition of bonding strength between the matrices and the CFO mesocrystals rather than the lattice mismatch. When embedded in a matrix with a higher melting point or stiffness, the CFO mesocrystal experiences higher out-of-plane compressive strain and shows a stronger magnetic anisotropy as well as cation site-exchange. Our study suggests a new pathway to tailor the functionalities of mesocrystals.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Tuning the functionalities of a mesocrystal via structural coupling

Liu

Tsai

et al. 2015

Sci Rep

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“…The CFO-PTO nanostructure has a lower PTO Raman intensity than pure PTO film, which implies the PTO Raman oscillator strength decreases. The larger band gap of PTO 39,40 than that of CFO 41,42 might cause the Raman response function v 00 to decrease. Additionally, high strains and small grains of PTO could cause phonon softening.…”

Section: Resultsmentioning

confidence: 99%

Anisotropic strain, magnetic properties, and lattice dynamics in self-assembled multiferroic CoFe2O4-PbTiO3 nanostructures

Tsai

Chen

Chang

et al. 2014

Journal of Applied Physics

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“…CoFe 2 O 4 , a ferromagnetic-semiconductor with n-type conductivity, can be a potential candidate for studying magnetic field effect induced tuning of the PEC properties owing to its high magnetostriction 21 , high rate of change of strain with magnetic field 22 , moderate saturation magnetization 23 and an optical bandgap in the visible light region 24,25 . CoFe 2 O 4 has inverse spinel structure where, Co 2+ ions occupy the octahedral sites and half of the Fe 3+ ions occupy the tetrahedral sites and remaining half of the Fe 3+ ions occupy the octahedral sites.…”

Section: Introductionmentioning

confidence: 99%

Low field magneto-tunable photocurrent in CoFe2O4 nanostructure films for enhanced photoelectrochemical properties

Singh¹,

Khare²

2018

Sci Rep

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Efficient solar to hydrogen conversion using photoelectrochemical (PEC) process requires semiconducting photoelectrodes with advanced functionalities, while exhibiting high optical absorption and charge transport properties. Herein, we demonstrate magneto-tunable photocurrent in CoFe2O4 nanostructure film under low applied magnetic fields for efficient PEC properties. Photocurrent is enhanced from ~1.55 mA/cm2 to ~3.47 mA/cm2 upon the application of external magnetic field of 600 Oe leading to ~123% enhancement. This enhancement in the photocurrent is attributed to the reduction of optical bandgap and increase in the depletion width at CoFe2O4/electrolyte interface resulting in an enhanced generation and separation of the photoexcited charge carriers. The reduction of optical bandgap in the presence of magnetic field is correlated to the shifting of Co2+ ions from octahedral to tetrahedral sites which is supported by the Raman spectroscopy results. Electrochemical impedance spectroscopy results confirm a decrease in the charge transfer resistance at the CoFe2O4/electrolyte interface in the presence of magnetic field. This work evidences a coupling of photoexcitation properties with magnetic properties of a ferromagnetic-semiconductor and the effect can be termed as magnetophototronic effect.

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Electronic structure and optical band gap of CoFe2O4 thin films

Cited by 61 publications

References 23 publications

Tuning the functionalities of a mesocrystal via structural coupling

Tuning the functionalities of a mesocrystal via structural coupling

Anisotropic strain, magnetic properties, and lattice dynamics in self-assembled multiferroic CoFe2O4-PbTiO3 nanostructures

Low field magneto-tunable photocurrent in CoFe2O4 nanostructure films for enhanced photoelectrochemical properties

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