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Iliev, M. N.; Mazumdar, Dipanjan; X., J.; Gupta, Arunava; Rigato, F.; Fontcuberta, J.

doi:10.1103/physrevb.83.014108

Cited by 81 publications

(67 citation statements)

References 18 publications

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“…hand, we observe a low wavenumber shift for the CFO band in the nanostructure, which lets us to suggest that the strong A 1g at  694 cm -1 of CFO presents a more complex relationship than that proposed in ref 15 , which deserves further experimental and theoretical attention. Due to the extreme versatility of Raman spectroscopy, we envisage that experiment aim to monitor electric/magnetic-induced changes of strain states and thus elastic coupling could be possible.…”

Section: /9supporting

confidence: 52%

Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

Chaix‐Pluchery

Cochard

Jadhav

et al. 2011

Applied Physics Letters

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We report a Raman scattering investigation of columnar BiFeO 3 -CoFe 2 O 4 (BFO-CFO) epitaxial thin film nanostructures, where BFO pillars are embedded in a CFO matrix. The feasibility of a strain analysis is illustrated through an investigation of two nanostructures with different BFO-CFO ratios. We show that the CFO matrix presents the same strain state in both nanostructures, while the strain state of the BFO pillars depends on the BFO/CFO ratio with an increasing tensile strain along the out-of-plane direction with decreasing BFO content.Our results demonstrate that Raman scattering allows monitoring strain states in complex 3D multiferroic pillar/matrix composites.

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Section: /9supporting

confidence: 52%

Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

Chaix‐Pluchery

Cochard

Jadhav

et al. 2011

Applied Physics Letters

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“…We also note that recent Raman investigations of both NFO single crystals 21 and NFO thin films 22 have provided evidence for short range cation order on the B sites compatible with P4 1 22 symmetry (or equivalently P4 3 22). Indeed, we find this to be the lowest energy configuration for both CFO and NFO over the whole investigated strain region.…”

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confidence: 99%

“…Furthermore, for both NFO and CFO, we find the (fully inverse) B site ordered arrangement with P4 1 22 symmetry to be energetically most favorable, consistent with recent experimental results for NFO. 21,22 Our results provide a reference for the interpretation of experimental data on CFO and NFO thin films and thus contribute to a better understanding of these materials as part of magnetic tunnelling junctions and spin-filter devices. …”

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Effect of epitaxial strain on the cation distribution in spinel ferrites CoFe₂O₄ and NiFe₂O₄: A density functional theory study

Fritsch¹,

Ederer²

2011

Appl. Phys. Lett.

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The effect of epitaxial strain on the cation distribution in spinel ferrites CoFe 2 O 4 and NiFe 2 O 4 is investigated by GGAþU total energy calculations. We obtain a very strong (moderate) tendency for cation inversion in NiFe 2 O 4 (CoFe 2 O 4 ), in agreement with experimental bulk studies. This preference for the inverse spinel structure is reduced by tensile epitaxial strain, which can lead to strong sensitivity of the cation distribution on specific growth conditions in thin films. Furthermore, we obtain significant energy differences between different cation arrangements with the same degree of inversion, providing further evidence for recently proposed short range B site order in [3][4][5][6][7] These applications require the growth of high quality thin films of CFO and NFO on suitable substrates. However, the electronic and magnetic properties of the corresponding films can depend strongly on substrate, film thickness, and specific preparation conditions, and eventually differ drastically from the corresponding bulk materials. For example, both increased and decreased saturation magnetizations have been reported for thin films of CFO and NFO grown on different substrates at different growth temperatures. [8][9][10] It has been suggested that the large increase in magnetization observed in some NFO films is due to the presence of Ni 2þ on the tetrahedrally coordinated cation sites of the spinel crystal structure. 8,9 The spinel crystal structure (space group Fd 3m) contains two inequivalent cation sites, the tetrahedrally coordinated A sites (T d ) and the octahedrally coordinated B sites (O h ). In the normal spinel structure, A and B sites are both occupied by a unique cation species. In the inverse spinel structure, the more abundant cation species (Fe 3þ in the present case) occupies the tetrahedral A sites and 50% of the octahedral B sites, whereas the remaining 50% of B sites are occupied by the other cation species (Co 2þ or Ni 2þ in the present case). In practice, site occupancies can vary between these two cases, depending on specific preparation conditions, and the inversion parameter k measures the fraction of less abundant cations on the B site sublattice, i.e., k ¼ 0 for the normal spinel structure and k ¼ 1 for complete inversion. Since in the ferrimagnetic Néel state of CFO and NFO, the magnetic moments of the A and B sublattices are oriented antiparallel to each other, small changes in k can lead to significant changes in magnetization.Here, we use first principles density functional theory to clarify whether epitaxial strain can influence the distribution of cations over the two different cation sites in CFO and NFO. Such epitaxial strain is generally incorporated in thin films due to the mismatch of lattice constants between the film material and the substrate, and often leads to drastic changes of properties compared to the corresponding bulk materials. 2 In order to accommodate different arrangements of cations on the tetrahedral and octahedral sites in our calculations, corresponding...

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“…The arrangement of transition metal ions in oxide magnetic materials plays a crucial role on its structure as well as on physical properties [1][2][3]. In particular the arrangement of transition metal ions in tetrahedral and/or octahedral sites of spinel structure is very appealing.…”

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Electronic structure and optical band gap of CoFe2O4 thin films

Ravindra

Padhan

Prellier

2012

Applied Physics Letters

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Electronic structure and optical band gap of thin films grown on 001 oriented have been investigated. Surprisingly, these films show additionalRaman modes at room temperature as compared to a bulk spinel structure. The splitting of Raman modes is explained by considering the short-range ordering of Co and Fe cations in octahedral site of spinel structure. In addition, an expansion of band-gap is observed with the reduction of film thickness, which is explained by the quantum size effect and misfit dislocation. Such results provide interesting insights for the growth of spinel phases.

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MonitoringB-site ordering and strain relaxation in NiFe2O4

Cited by 81 publications

References 18 publications

Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

Effect of epitaxial strain on the cation distribution in spinel ferrites CoFe₂O₄ and NiFe₂O₄: A density functional theory study

Electronic structure and optical band gap of CoFe2O4 thin films

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MonitoringB-site ordering and strain relaxation in NiFe2O4

Cited by 81 publications

References 18 publications

Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

Effect of epitaxial strain on the cation distribution in spinel ferrites CoFe2O4 and NiFe2O4: A density functional theory study

Electronic structure and optical band gap of CoFe2O4 thin films

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Effect of epitaxial strain on the cation distribution in spinel ferrites CoFe₂O₄ and NiFe₂O₄: A density functional theory study