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Ziatdinov M, Banerjee A, Maksov A, Berlijn T, Zhou W, Cao HB, Yan JQ, Bridges CA, Mandrus DG, Nagler SE, Baddorf AP, Kalinin SV. Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl 3. Nat Commun 2016; 7:13774. [PMID: 27941761 PMCID: PMC5159869 DOI: 10.1038/ncomms13774] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 11/01/2016] [Indexed: 01/24/2023] Open
Abstract
A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, α-RuCl3. Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of α-RuCl3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at the nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of ≈0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual α-RuCl3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface.
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Affiliation(s)
- M Ziatdinov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A Banerjee
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A Maksov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Bredesen Center for Interdisciplinary Research, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - T Berlijn
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - W Zhou
- Material Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H B Cao
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J-Q Yan
- Material Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Department of Material Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - C A Bridges
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - D G Mandrus
- Material Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Department of Material Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - S E Nagler
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Bredesen Center for Interdisciplinary Research, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - A P Baddorf
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - S V Kalinin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Bredesen Center for Interdisciplinary Research, University of Tennessee, Knoxville, Tennessee 37996, USA
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Kalinin SV, Shin J, Kachanov M, Karapetian E, Baddorf AP. Nanoelectromechanics of Piezoresponse Force Microscopy: Contact Properties, Fields Below the Surface and Polarization Switching. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-784-c2.6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTTo achieve quantitative interpretation of Piezoresponse Force Microscopy (PFM), including resolution limits, tip bias- and strain-induced phenomena and spectroscopy, knowledge of elastic and electrostatic field distributions below the tip is required. The exact closed form solution of the coupled electroelastic problem for piezoelectric indentation is derived and used to obtain the tip-induced electric field and strain distribution in the ferroelectric material. This establishes a complete continuum mechanics description of the PFM imaging mechanism. These solutions are reduced to the point charge/force behavior for large separations from contact, and the applicability limits and charge/force magnitude for these models are established. The implications of these results for ferroelectric polarization switching processes are analyzed.
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Seidel J, Maksymovych P, Batra Y, Katan A, Yang SY, He Q, Baddorf AP, Kalinin SV, Yang CH, Yang JC, Chu YH, Salje EKH, Wormeester H, Salmeron M, Ramesh R. Domain wall conductivity in La-doped BiFeO3. Phys Rev Lett 2010; 105:197603. [PMID: 21231197 DOI: 10.1103/physrevlett.105.197603] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Indexed: 05/30/2023]
Abstract
The transport physics of domain wall conductivity in La-doped bismuth ferrite (BiFeO3) has been probed using variable temperature conducting atomic force microscopy and piezoresponse force microscopy in samples with arrays of domain walls in the as-grown state. Nanoscale current measurements are investigated as a function of bias and temperature and are shown to be consistent with distinct electronic properties at the domain walls leading to changes in the observed local conductivity. Our observation is well described within a band picture of the observed electronic conduction. Finally, we demonstrate an additional degree of control of the wall conductivity through chemical doping with oxygen vacancies, thus influencing the local conductive state.
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Affiliation(s)
- J Seidel
- Department of Physics, University of California, Berkeley, California 94720, USA
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Balke N, Choudhury S, Jesse S, Huijben M, Chu YH, Baddorf AP, Chen LQ, Ramesh R, Kalinin SV. Deterministic control of ferroelastic switching in multiferroic materials. Nat Nanotechnol 2009; 4:868-75. [PMID: 19893529 DOI: 10.1038/nnano.2009.293] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Accepted: 09/03/2009] [Indexed: 05/22/2023]
Abstract
Multiferroic materials showing coupled electric, magnetic and elastic orderings provide a platform to explore complexity and new paradigms for memory and logic devices. Until now, the deterministic control of non-ferroelectric order parameters in multiferroics has been elusive. Here, we demonstrate deterministic ferroelastic switching in rhombohedral BiFeO(3) by domain nucleation with a scanning probe. We are able to select among final states that have the same electrostatic energy, but differ dramatically in elastic or magnetic order, by applying voltage to the probe while it is in lateral motion. We also demonstrate the controlled creation of a ferrotoroidal order parameter. The ability to control local elastic, magnetic and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based and strain-coupled devices.
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Affiliation(s)
- N Balke
- The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Yang CH, Seidel J, Kim SY, Rossen PB, Yu P, Gajek M, Chu YH, Martin LW, Holcomb MB, He Q, Maksymovych P, Balke N, Kalinin SV, Baddorf AP, Basu SR, Scullin ML, Ramesh R. Electric modulation of conduction in multiferroic Ca-doped BiFeO3 films. Nat Mater 2009; 8:485-93. [PMID: 19396162 DOI: 10.1038/nmat2432] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Accepted: 03/20/2009] [Indexed: 05/12/2023]
Abstract
Many interesting materials phenomena such as the emergence of high-Tc superconductivity in the cuprates and colossal magnetoresistance in the manganites arise out of a doping-driven competition between energetically similar ground states. Doped multiferroics present a tantalizing evolution of this generic concept of phase competition. Here, we present the observation of an electronic conductor-insulator transition by control of band-filling in the model antiferromagnetic ferroelectric BiFeO3 through Ca doping. Application of electric field enables us to control and manipulate this electronic transition to the extent that a p-n junction can be created, erased and inverted in this material. A 'dome-like' feature in the doping dependence of the ferroelectric transition is observed around a Ca concentration of approximately 1/8, where a new pseudo-tetragonal phase appears and the electric modulation of conduction is optimized. Possible mechanisms for the observed effects are discussed on the basis of the interplay of ionic and electronic conduction. This observation opens the door to merging magnetoelectrics and magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom already present in the multiferroic BiFeO3.
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Affiliation(s)
- C-H Yang
- Department of Physics, University of California, Berkeley, California 94720, USA.
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Rodriguez BJ, Jesse S, Baddorf AP, Kim SH, Kalinin SV. Controlling polarization dynamics in a liquid environment: from localized to macroscopic switching in ferroelectrics. Phys Rev Lett 2007; 98:247603. [PMID: 17677994 DOI: 10.1103/physrevlett.98.247603] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Indexed: 05/16/2023]
Abstract
The effect of disorder on polarization switching in ferroelectric materials is studied using piezoresponse force microscopy in a liquid environment. The spatial extent of the electric field created by a biased tip is controlled by the choice of medium, resulting in a transition from localized switching dictated by tip radius, to uniform switching across the film. In the localized regime, the formation of fractal domains has been observed with dimensionality controlled by the length scale of the frozen disorder. In the nonlocal regime, preferential nucleation at defect sites and the presence of long-range correlations has been observed.
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Affiliation(s)
- B J Rodriguez
- Materials Science and Technology Division and The Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Kalinin SV, Jesse S, Rodriguez BJ, Shin J, Baddorf AP, Lee HN, Borisevich A, Pennycook SJ. Spatial resolution, information limit, and contrast transfer in piezoresponse force microscopy. Nanotechnology 2006; 17:3400-11. [PMID: 19661582 DOI: 10.1088/0957-4484/17/14/010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Scanning probe-based ferroelectric domain imaging and patterning has attracted broad attention for use in the characterization of ferroelectric materials, ultrahigh density data storage, and nanofabrication. The viability of these applications is limited by the minimal domain size that can be fabricated and reliably detected by scanning probe microscopy. Here, the contrast transfer mechanism in piezoresponse force microscopy (PFM) of ferroelectric materials is analysed in detail. A consistent definition of resolution is developed both for the writing and the imaging processes, and the concept of an information limit in PFM is established. Experimental determination of the object transfer function and the subsequent reconstruction of an 'ideal image' is demonstrated. This contrast transfer theory provides a quantitative basis for image interpretation and allows for the comparison of different instruments in PFM. It is shown that experimentally observed domain sizes can be limited by the resolution of the scanning probe microscope to the order of tens of nanometres even though smaller domains, of the order of several nanometres, can be created.
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Rodriguez BJ, Jesse S, Baddorf AP, Kalinin SV. High resolution electromechanical imaging of ferroelectric materials in a liquid environment by piezoresponse force microscopy. Phys Rev Lett 2006; 96:237602. [PMID: 16803404 DOI: 10.1103/physrevlett.96.237602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Indexed: 05/10/2023]
Abstract
High-resolution imaging of ferroelectric materials using piezoresponse force microscopy (PFM) is demonstrated in an aqueous environment. The elimination of both long-range electrostatic forces and capillary interactions results in a localization of the ac field to the tip-surface junction and allows the tip-surface contact area to be controlled. This approach results in spatial resolutions approaching the limit of the intrinsic domain-wall width. Imaging at frequencies corresponding to high-order cantilever resonances minimizes the viscous damping and added mass effects on cantilever dynamics and allows sensitivities comparable to ambient conditions. PFM in liquids will provide novel opportunities for high-resolution studies of ferroelectric materials, imaging of soft polymer materials, and imaging of biological systems in physiological environments on, ultimately, the molecular level.
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Affiliation(s)
- Brian J Rodriguez
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Kalinin SV, Rodriguez BJ, Shin J, Jesse S, Grichko V, Thundat T, Baddorf AP, Gruverman A. Bioelectromechanical imaging by scanning probe microscopy: Galvani's experiment at the nanoscale. Ultramicroscopy 2006; 106:334-40. [PMID: 16387441 DOI: 10.1016/j.ultramic.2005.10.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Revised: 10/25/2005] [Accepted: 10/26/2005] [Indexed: 11/25/2022]
Abstract
Since the discovery in the late 18th century of electrically induced mechanical response in muscle tissue, coupling between electrical and mechanical phenomena has been shown to be a near-universal feature of biological systems. Here, we employ scanning probe microscopy (SPM) to measure the sub-Angstrom mechanical response of a biological system induced by an electric bias applied to a conductive SPM tip. Visualization of the spiral shape and orientation of protein fibrils with 5 nm spatial resolution in a human tooth and chitin molecular bundle orientation in a butterfly wing is demonstrated. In particular, the applicability of SPM-based techniques for the determination of molecular orientation is discussed.
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Affiliation(s)
- Sergei V Kalinin
- Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Rodriguez BJ, Kalinin SV, Shin J, Jesse S, Grichko V, Thundat T, Baddorf AP, Gruverman A. Electromechanical imaging of biomaterials by scanning probe microscopy. J Struct Biol 2006; 153:151-9. [PMID: 16403652 DOI: 10.1016/j.jsb.2005.10.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2005] [Revised: 09/23/2005] [Accepted: 10/04/2005] [Indexed: 10/25/2022]
Abstract
The majority of calcified and connective tissues possess complex hierarchical structure spanning the length scales from nanometers to millimeters. Understanding the biological functionality of these materials requires reliable methods for structural imaging on the nanoscale. Here, we demonstrate an approach for electromechanical imaging of the structure of biological samples on the length scales from tens of microns to nanometers using piezoresponse force microscopy (PFM), which utilizes the intrinsic piezoelectricity of biopolymers such as proteins and polysaccharides as the basis for high-resolution imaging. Nanostructural imaging of a variety of protein-based materials, including tooth, antler, and cartilage, is demonstrated. Visualization of protein fibrils with sub-10nm spatial resolution in a human tooth is achieved. Given the near-ubiquitous presence of piezoelectricity in biological systems, PFM is suggested as a versatile tool for micro- and nanostructural imaging in both connective and calcified tissues.
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Affiliation(s)
- B J Rodriguez
- Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Farnan GA, Fu CL, Gai Z, Krcmar M, Baddorf AP, Zhang Z, Shen J. Electronic stability of magnetic Fe/Co superlattices with monatomic layer alternation. Phys Rev Lett 2003; 91:226106. [PMID: 14683255 DOI: 10.1103/physrevlett.91.226106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2003] [Indexed: 05/24/2023]
Abstract
We report a surprising observation that the growth of the [Fe(1 ML)/Co(1 ML)](n) superlattice of L1(0) structure on Cu(100) is stable only up to six atomic layers (n=3), which cannot be rationalized by stress arguments. Instead, first-principles calculations reveal a transition from the L1(0) to the B2 structure due to the effect of dimensionality on the stability of the electronic structure of the superlattice. Whereas the majority-spin electrons are energetically insensitive to the layer thickness, the minority-spin electrons induce the transition at n=3.
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Affiliation(s)
- G A Farnan
- Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Baddorf AP, Swan AK, Wendelken JF. Comment on "In-plane lattice reconstruction of Cu(001)". Phys Rev Lett 1996; 76:3658. [PMID: 10061026 DOI: 10.1103/physrevlett.76.3658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Helgesen G, Gibbs D, Baddorf AP, Zehner DM, Mochrie SG. X-ray reflectivity of the Cu(110) surface. Phys Rev B Condens Matter 1993; 48:15320-15325. [PMID: 10008070 DOI: 10.1103/physrevb.48.15320] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Baddorf AP, Zehner DM, Helgesen G, Gibbs D, Sandy AR, Mochrie SG. X-ray-scattering determination of the Cu(110)-(2 x 3)N structure. Phys Rev B Condens Matter 1993; 48:9013-9020. [PMID: 10007121 DOI: 10.1103/physrevb.48.9013] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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