Quantitative strain analysis and growth mode of pulsed laser deposited epitaxial CoFe2O4 thin films

Axelsson, Anna‐Karin; Aguesse, Frédéric; Spillane, Liam; Valant, Matjaž; McComb, David W.; Alford, Neil McN.

doi:10.1016/j.actamat.2010.09.052

Cited by 22 publications

(7 citation statements)

References 13 publications

(13 reference statements)

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“…From first view, one could anticipate that stress effects on unit‐cell metrics and bond topology could be more relevant in oxide‐based open structures, such as the spinel, than in the more densely packed perovskite structure. Probably for this reason, the Poisson ratio of spinel‐based thin films has recently received much attention 19–21. Somehow in agreement with views just described, it has been reported that thin films of CoFe 2 O 4, a prototypical spinel‐ferrite oxide, grown on a perovskite (SrTiO 3 ) substrate, could be auxetic, i.e., display a negative Poisson ratio ( ν < 0) 19.…”

Section: Introductionsupporting

confidence: 56%

The Poisson Ratio in CoFe₂O₄ Spinel Thin Films

Foerster

Iliev

Dix

et al. 2012

Adv Funct Materials

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The response of epitaxial CoFe2O4 thin films to biaxial compressive stress imposed by MgAl2O4 and SrTiO3 single crystalline substrates is studied using X‐ray diffraction and Raman spectroscopy. It is found that the Poisson ratio ν signals a non‐auxetic behavior and depends on the substrate used. The Raman modes show an increase in frequency when increasing compressive strain by reducing film thickness; this is due to the shrinking of the unit cell volume. Such behavior is in qualitative agreement with recent ab initio calculations, although the measured values are significantly smaller than predictions. In contrast, the measured Poisson ratio is found to be in good agreement with expectations based on general arguments of atomic packing density. Possible guidelines for searching auxetic response in materials with spinel structure are discussed.

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Section: Introductionsupporting

confidence: 56%

The Poisson Ratio in CoFe₂O₄ Spinel Thin Films

Foerster

Iliev

Dix

et al. 2012

Adv Funct Materials

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“…where b is the magnitude of the Burgers vector, f is the bulk lattice mismatch, v is Poisson's ratio, α is the angle between the dislocation line and its Burgers vector, and λ is the angle between the slip direction and the Burgers vector. Taking f = 0.038, v = 0.26 [61], b = 4.195 Å, α = π/2, and λ = 0 [62], h c ∼ 5 nm, which is comparable to the shell thicknesses obtained from micromagnetic simulations and SANS. We expect variation of the displacement field toward the center of a pillar of a magnetostrictive material like the CFO will produce nonuniform magnetization and the length scales of the displacement field and magnetic nonuniformity will be related.…”

supporting

confidence: 77%

Nanoscale magnetization inhomogeneity within single phase nanopillars

Farmer

Guo

Desautels

et al. 2019

Phys. Rev. Materials

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We report observation of a radial dependence in the magnetic anisotropy of epitaxially strained CoFe 2 O 4 nanopillars in a BaTiO 3 matrix. This archetypal example of a multiferroic heterostructure with a self-assembling three-dimensional architecture possesses significant out-of-plane uniaxial magnetic anisotropy. The anisotropy originates from the large magnetostriction of CoFe 2 O 4 and the state of stress within the nanocomposite. Magnetometry suggests the existence of two magnetic phases with different anisotropies. Micromagnetic simulations of a core-shell magnetic anisotropy qualitatively reproduce features of the magnetic hysteresis and elucidate the magnetization reversal mechanism: The magnetization initially reorients within the pillar core, followed by that of the shell. This is consistent with polarized small-angle neutron scattering which can be described by a CoFe 2 O 4 magnetization that is nonuniform on nanometer length scales. As the length scale of inhomogeneity of the magnetic anisotropy is similar to estimates of the relaxation of the displacement field from the CoFe 2 O 4 -BaTiO 3 interface, stress and its influence on structure provide an important route to new functionality of vertically aligned nanopillars for applications in low-power memory, computing, and sensing.

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“…The fact that the lowest energy planes of perovskites and spinels ({001} in the former and {111} in the latter) differ is likely the driving force for the reported columnar growth. 24,31 It could be tempting to argue that defective intercolumnar areas could constitute low energy paths for the diffusion of the small Ti 4+ ions. Indeed, as mentioned above, Mg 2+ interdiffusion between MgO substrates and some ferrites had been documented; [10][11][12][13][14][15]32 therefore, Ti 4+ being smaller than Mg 2+ , it should not be a surprise to observe Ti migration through CFO as found here in CS, CS 1 M and CS 2 M samples.…”

Section: Discussionmentioning

confidence: 99%

Ti diffusion in (001) SrTiO3–CoFe2O4 epitaxial heterostructures: blocking role of a MgAl2O4 buffer

Rebled

Foerster

Estradé

et al. 2013

Phys. Chem. Chem. Phys.

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Titanium diffusion from (001) SrTiO3 (STO) substrates into CoFe2O4 (CFO) films grown using pulsed laser deposition is reported. To elucidate the reasons for Ti interdiffusion, a comparative study of CFO films grown on MgAl2O4 (MAO) and STO substrates, buffered by thin STO and MAO layers, has been made. It is shown that whereas bottom STO layers always result in Ti migration, a thin MAO layer, only 8 nm thick, is effective in blocking it. We argue that this success relies on the lower mobility of Ti ions in the MAO lattice compared to that of CFO. This result should contribute to the development of high quality epitaxial heterostructures of dissimilar complex oxides.

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Quantitative strain analysis and growth mode of pulsed laser deposited epitaxial CoFe2O4 thin films

Cited by 22 publications

References 13 publications

The Poisson Ratio in CoFe₂O₄ Spinel Thin Films

The Poisson Ratio in CoFe₂O₄ Spinel Thin Films

Nanoscale magnetization inhomogeneity within single phase nanopillars

Ti diffusion in (001) SrTiO3–CoFe2O4 epitaxial heterostructures: blocking role of a MgAl2O4 buffer

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Quantitative strain analysis and growth mode of pulsed laser deposited epitaxial CoFe2O4 thin films

Cited by 22 publications

References 13 publications

The Poisson Ratio in CoFe2O4 Spinel Thin Films

The Poisson Ratio in CoFe2O4 Spinel Thin Films

Nanoscale magnetization inhomogeneity within single phase nanopillars

Ti diffusion in (001) SrTiO3–CoFe2O4 epitaxial heterostructures: blocking role of a MgAl2O4 buffer

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The Poisson Ratio in CoFe₂O₄ Spinel Thin Films

The Poisson Ratio in CoFe₂O₄ Spinel Thin Films