Ferroelectric size effects in multiferroic BiFeO3 thin films

Chu, Ying Hao; Zhao, Tong; Cruz, M. P.; Zhan, Qian; Yang, Pingxiong; Martin, Lane W.; Huijben, Mark; Yang, Chul–Su; Zavaliche, F.; Zheng, Haimei; Ramesh, R.

doi:10.1063/1.2750524

Cited by 186 publications

(134 citation statements)

References 19 publications

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“…The full width at half maximum of the rocking curve of the (006) h reflection ( fig. 1(c)) is 0.12 • , which is comparably narrow in comparison to reported values for films grown by sputtering [21,22], pulsed laser deposition [20,21,32] and molecular beam epitaxy [33], confirms the high crystalline quality of the films. This is however still four times as broad as for a bulk single crystal, indicating the presence of strain, inhomogeneity or mosaic spread.…”

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confidence: 57%

Coherent Magnetoelastic Domains in Multiferroic BiFeO3 Films

et al. 2016

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The physical properties of epitaxial films can fundamentally differ from those of bulk single crystals even above the critical thickness. By a combination of non-resonant x-ray magnetic scattering, neutron diffraction and vector-mapped x-ray magnetic linear dichroism photoemission electron microscopy, we show that epitaxial (111)-BiFeO 3 films support sub-micron antiferromagnetic domains, which are magneto-elastically coupled to a coherent crystallographic monoclinic twin structure. This unique texture, which is absent in bulk single crystals, should enable control of magnetism in BiFeO 3 film devices via epitaxial strain.PACS numbers: 77.55. Nv, 68.37.Yz, 75.60.Ch, Electrical manipulation of spins in insulators is a promising route to a new generation of fast, low consumption electronics [1][2][3]. Although direct electrical control of ferromagnets is challenging, much progress has been made towards electrical switching of antiferromagnetic spins [4]. Multiferroic BiFeO 3 (BFO) is one of the most promising materials: at room temperature, BFO is both ferroelectric and antiferromagnetic, and its spins can be rotated by switching the direction of the electrical polarisation [5,6]. Thus far, a fundamental limitation towards practical BFO devices has been the lack of understanding of the interplay between ferroelectricity, ferromagnetism and lattice distortions (ferroelasticity). Using a combination of non-resonant x-ray magnetic scattering (NXMS), neutron diffraction and vectormapped x-ray magnetic linear dichroism photoemission electron microscopy (XMLD-PEEM), we show that the antiferromagnetic domain structure of 1 µm thick, epitaxial (111)-oriented BFO films displays a ≈100 nm-scale texture, dramatically different from the mm-size features in bulk single crystals. We also demonstrate that this magnetic texture is coherent (having matching topography and symmetry elements) with a pattern of monoclinic domains at the nanoscale. This texture is reminiscent of the dense polydomain states that are thermodynamically stable in ferroelectric perovskites such as PbTiO 3 in the presence of strain misfit [7]. This strongly suggests that the relaxed (111)-oriented BFO structure is not trigonal, but is a texture of coherent monoclinic micro twins. Besides providing a new pathway towards strainengineering multiferroic domains in BFO, our approach yielded a detailed picture of the interplay between magnetism and lattice over 5 orders of magnitude in length * p.g.radaelli@physics.ox.ac.uk scales, and could be applied to many classes of functional magnetic oxide devices.Below its ferroelectric Curie temperature of T C = 1103 K, bulk BFO is generally believed to possess a rhombohedrally-distorted perovskite structure with space group R3c (pictured in fig. 1(a) and (b)) [8,9], although very recent high-resolution synchrotron measurements have suggested a small monoclinic distortion [10]. The Bi 3+ and Fe 3+ cations are displaced away from their centrosymmetric positions along the (111) (pseudocubic setting) axis [11], producing a ...

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confidence: 57%

Coherent Magnetoelastic Domains in Multiferroic BiFeO3 Films

et al. 2016

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“…Out-of-plane PFM measurements show that all the films are polarized down, also in agreement with previous reports. 18 In Fig. 2͑b͒, inplane PFM ͑IP-PFM͒ images of the same films are shown.…”

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confidence: 99%

“…1͑c͔͒ in agreement with previous reports. 18 We have been able to understand why. This is confirmed by PFM imaging ͓Fig.…”

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confidence: 99%

Tuning the atomic and domain structure of epitaxial films of multiferroicBiFeO3

et al. 2010

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Recent works have shown that the domain walls of room-temperature multiferroic BiFeO 3 ͑BFO͒ thin films can display distinct and promising functionalities. It is thus important to understand the mechanisms underlying domain formation in these films. High-resolution x-ray diffraction and piezoforce microscopy, combined with first-principles simulations, have allowed us to characterize both the atomic and domain structure of BFO films grown under compressive strain on ͑001͒-SrTiO 3 , as a function of thickness. The clamping of the substrate has been observed to exist in two different regimes: ultrathin, d Ͻ 18 nm, and thin, d Ͼ 18 nm. When this is taken into account in the calculations, an excellent agreement between the predicted and observed lattice parameters is shown. We derive a twinning model that describes the experimental observations and could explain why the 71°domain walls are the only ones showing insulating character. This understanding of the exact mechanism for domain formation provides us with a new degree of freedom to control the structure and, thus, the properties of BiFeO 3 thin films.

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“…Its lead-free nature and large remanent polarization [4] have already motivated Fujitsu to use it as the active layer in prototype ferroelectric memories [5]; also, sublattice magnetic switching using voltage has been demonstrated [6], which may find its way into spintronic applications via exchange bias [7]. The possible coupling between ferroelectric and antiferromagnetic domains has triggered a flurry of work on the morphology and functional properties of the domains [6,[8][9][10][11]. Standard BFO films are generally found to have straightwalled domains which follow the well-known scaling law of Landau, Lifshitz, and Kittel (LLK) [12 -14], that is, domain width grows proportionally to the square root of film thickness [10].…”

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Fractal Dimension and Size Scaling of Domains in Thin Films of MultiferroicBiFeO3

et al. 2008

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Domains in ferroelectric films are usually smooth, stripelike, very thin compared with magnetic ones, and satisfy the Landau-Lifshitz-Kittel scaling law (width proportional to square root of film thickness). However, the ferroelectric domains in very thin films of multiferroic BiFeO 3 have irregular domain walls characterized by a roughness exponent 0.5-0.6 and in-plane fractal Hausdorff dimension H jj 1:4 0:1, and the domain size scales with an exponent 0:59 0:08 rather than 1 2 . The domains are significantly larger than those of other ferroelectrics of the same thickness, and closer in size to those of magnetic materials, which is consistent with a strong magnetoelectric coupling at the walls. A general model is proposed for ferroelectrics, ferroelastics or ferromagnetic domains which relates the fractal dimension of the walls to domain size scaling.

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Ferroelectric size effects in multiferroic BiFeO3 thin films

Cited by 186 publications

References 19 publications

Coherent Magnetoelastic Domains in Multiferroic BiFeO3 Films

Coherent Magnetoelastic Domains in Multiferroic BiFeO3 Films

Tuning the atomic and domain structure of epitaxial films of multiferroicBiFeO3

Fractal Dimension and Size Scaling of Domains in Thin Films of MultiferroicBiFeO3

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