Pillar shape modulation in epitaxial BiFeO3–CoFe2O4 vertical nanocomposite films

Kim, Dong Hun; Aimon, Nicolas M.; Ross, Caroline A.

doi:10.1063/1.4892695

Cited by 16 publications

(20 citation statements)

References 18 publications

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“…The total magnetic anisotropy (51 kOe) is dominated by the strain effect. Magnetic anisotropy of CFO and NiFe 2 O 4 (NFO) based nanocomposites have been widely studied and it is controlled by the compressive vertical strain . The direct growth of BFO:CFO VANs on LAO results in a majority of the BFO tetragonal phase.…”

Section: Functionality Tuning Driven By Strain Defect and Interfacementioning

confidence: 99%

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

et al. 2018

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Complex metal oxides, which show a variety of functional properties such as ferromagnetism, ferroelectricity, multi-ferroelectricity, superconductivity, and ionic conduction, have attracted much attention in the past decades. These exotic physical properties arise from a complex hierarchy of competing interactions among spin, charge, orbital, and lattice degrees of freedom. The development of advanced characterization techniques such as electron microscopy, neutron scattering, synchrotron scattering and imaging, spectroscopy at high magnetic fields, and others has enabled us to study the interactions among these degrees of freedom coupled with strain, defect, and interface Vertically aligned nanocomposite thin films with ordered two phases, grown epitaxially on substrates, have attracted tremendous interest in the past decade. These unique nanostructured composite thin films with large vertical interfacial area, controllable vertical lattice strain, and defects provide an intriguing playground, allowing for the manipulation of a variety of functional properties of the materials via the interplay among strain, defect, and interface. This field has evolved from basic growth and characterization to functionality tuning as well as potential applications in energy conversion and information technology. Here, the remarkable progress achieved in vertically aligned nanocomposite thin films from a perspective of tuning functionalities through control of strain, defect, and interface is summarized. Thin FilmsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201803241. 12 11 12where c 11 and c 12 are elastic moduli of the film material. Epitaxial strain gradually changes with film thickness in perovskite manganites. Figure 3 shows reciprocal space mapping or RSM (103) of La 0.7 Ca 0.3 MnO 3 (LCMO) films on STO (001) substrates. It captures the gradual strain relaxation process with increasing film thickness in manganite thin films. When the film is very thin, the interface is coherent with

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Section: Functionality Tuning Driven By Strain Defect and Interfacementioning

confidence: 99%

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

et al. 2018

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“…Moreover, the magnetic properties of the nanostructures are strongly dependent on their shape, size, and spatial arrangement . Consequently, a large number of efforts have been made to control the order and geometry of the self‐assembled structures …”

Section: Introductionmentioning

confidence: 99%

“…Among many perovskite and spinel combinations, BiFeO 3 (BFO)‐CoFe 2 O 4 (CFO) nanocomposites are the most extensively studied . They can exhibit strong magnetoelectric coupling and may be useful in magnetoelectric memory or logic devices .…”

Section: Introductionmentioning

confidence: 99%

Structure, Ferroelectricity, and Magnetism in Self‐Assembled BiFeO₃–CoFe₂O₄ Nanocomposites on (110)‐LaAlO₃ Substrates

Tian

Ojha

Ning

et al. 2019

Adv Elect Materials

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grow as a tetragonal structure with a large c/a ratio (≈1.25) when the compressive epitaxial strain exceeds ≈4.5%, e.g., when grown on LaAlO 3 (LAO). [29] In previous work on BFO-CFO nanocomposites, (001)-oriented pseudocubic substrates were typically used, and there is little work on nanocomposites grown with (110) and (111) orientations. [21,31,32] The CFO nanopillars in nanocomposites grown on (110) and (111) substrates appear as tent-like structures and triangular prisms, respectively, in contrast to the rectangular pillars obtained on the (001)-oriented substrates. Moreover, BFO films grown on (110)-oriented LAO exhibit a uniaxial in-plane strain instead of the biaxial strain found in the (001) orientation, [33,34] and the strain along the [110] in-plane direction is relaxed even in BFO films with a thickness as low as ≈10 nm. BFO-CFO nanocomposite films on (110)-oriented LAO also exhibit strain in the out-of-plane direction of both phases that differs from the strain state obtained in single-phase films. A large out-of-plane strain significantly modifies the magnetism, magnetic anisotropy, and magnetotransport properties in vertical nanocomposite films. [10] In this article, we show that the BFO in a BFO-CFO nanocomposite grown on LAO (110) substrates forms different phases, rhombohedral-like (R-like) or tetragonal-like (T-like), depending on the thickness of the film and the effects of the vertical lattice strain between the BFO and CFO. A variety of domain structures were observed in the BFO matrix, and thickness-dependent magnetic properties of the CFO are interpreted in terms of the film strain and the shape of the CFO. These results demonstrate how the properties of nanocomposites including in-plane anisotropy can be engineered on a (110) substrate. Results and DiscussionA series of epitaxial BFO-CFO nanocomposite thin films with thickness of 25 to 75 nm was deposited on single-crystal LAO (110). The LAO is a rhombohedrally distorted perovskite at room temperature, with a pseudocubic lattice parameter of 3.787 Å. The (110)-oriented LAO substrate therefore has a rectangular surface net with dimensions 5.355 Å along the pseudocubic [110] sub direction and 3.787 Å along the [001] sub direction. The films were grown using pulsed laser deposition (PLD) as described in the Experimental Section. A conductive La(Sr 0.33 ,Mn 0.67 )O 3 (LSMO) layer ≈8 nm thick was first epitaxially grown on the substrate, followed by deposition of the A strain-driven BiFeO 3 (BFO) tetragonal to rhombohedral phase transition is demonstrated in self-assembled BiFeO 3 -CoFe 2 O 4 (BFO-CFO) nanocomposites on LaAlO 3 (110)-oriented substrates with varying thickness. The CFO forms parallel nanoscale fin-shaped structures within a BFO matrix. Out-of-plane lattice strain from the BFO/CFO interfaces stabilizes the BFO rhombohedrallike phase. The BFO exhibits a range of ferroelectric textures including stripe domains and centered domain arrangements, and the magnetic anisotropy of CFO shows a thickness-dependent reorientation.

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“…[21][22][23][24][25][26][27][28] Thus, designing new multiferroic nanocomposites requires an understanding of how domain structure and interaction dictate function, while synthesis requires the ability to control the relative phase compositions and morphologies. [15,17,21,24,25,[29][30][31][32][33][34][35] Light element Li doping is known to improve the piezoelectric properties in ferroelectric ceramics by shifting the morphotropic phase boundary to room temperature, however the mechanism driving this response is elusive. [36,37] Recently, Li doped bismuth ferrite (BiFeO 3 ) was reported to show room temperature ferromagnetism and spintronic functionality.…”

Section: Introductionmentioning

confidence: 99%

Self‐Assembled Room Temperature Multiferroic BiFeO₃‐LiFe₅O₈ Nanocomposites

Sharma

Agarwal

Collins

et al. 2019

Adv Funct Materials

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Multiferroic materials have driven significant research interest due to their promising technological potential. Developing new room-temperature multiferroics and understanding their fundamental properties are important to reveal unanticipated physical phenomena and potential applications. Here, a new room temperature multiferroic nanocomposite comprised of an ordered ferrimagnetic spinel α-LiFe 5 O 8 (LFO) and a ferroelectric perovskite BiFeO 3 (BFO) is presented. We This article is protected by copyright. All rights reserved. 3 observed that lithium (Li)-doping in BFO favors the formation of LFO spinel as a secondary phase during the synthesis of Li x Bi 1-x FeO 3 ceramics. Multimodal functional and chemical imaging methods are used to map the relationship between doping-induced phase separation and local ferroic properties in both the BFO-LFO composite ceramics and self-assembled nanocomposite thin films. The energetics of phase separation in Li doped BFO and the formation of BFO-LFO composites is supported by first principles calculations. These findings shed light on Li's role in the formation of a functionally important room temperature multiferroic and open a new approach in the synthesis of light element doped nanocomposites for future energy, sensing, and memory applications.

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Pillar shape modulation in epitaxial BiFeO3–CoFe2O4 vertical nanocomposite films

Cited by 16 publications

References 18 publications

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

Structure, Ferroelectricity, and Magnetism in Self‐Assembled BiFeO₃–CoFe₂O₄ Nanocomposites on (110)‐LaAlO₃ Substrates

Self‐Assembled Room Temperature Multiferroic BiFeO₃‐LiFe₅O₈ Nanocomposites

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Pillar shape modulation in epitaxial BiFeO3–CoFe2O4 vertical nanocomposite films

Cited by 16 publications

References 18 publications

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

Structure, Ferroelectricity, and Magnetism in Self‐Assembled BiFeO3–CoFe2O4 Nanocomposites on (110)‐LaAlO3 Substrates

Self‐Assembled Room Temperature Multiferroic BiFeO3‐LiFe5O8 Nanocomposites

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Structure, Ferroelectricity, and Magnetism in Self‐Assembled BiFeO₃–CoFe₂O₄ Nanocomposites on (110)‐LaAlO₃ Substrates

Self‐Assembled Room Temperature Multiferroic BiFeO₃‐LiFe₅O₈ Nanocomposites